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Iapetus Thermal Radiation Im
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| Description |
Iapetus Thermal Radiation Image |
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This image of the infrared heat radiation from Saturn's moon Iapetus was obtained by the Cassini composite infrared spectrometer instrument 16 hours before Cassini's closest approach to this mysterious moon, on December 31, 2004. The thermal radiation is shown as both a grayscale image, equivalent to what we would see if our eyes were sensitive to infrared wavelengths near 15 microns, and as a color-coded temperature map. A previously-released mosaic obtained by Cassini's imaging camera shortly before the composite infrared spectrometer observation, with similar scale and orientation, is also shown for comparison. Temperatures reach nearly 130 Kelvin (-226 Fahrenheit) at noon on the equator on the dark material that covers most of this side of Iapetus, making high noon on Iapetus's dark side probably the warmest places in the Saturn system. This is much warmer than temperatures on another Saturnian moon, Phoebe, measured by composite infrared spectrometer in June 2004. Those Phoebe temperature measurements peaked near 112 Kelvin (-258 Fahrenheit), because though Phoebe is almost as dark as Iapetus's dark material and absorbs nearly as much sunlight, Phoebe rotates much more quickly (once every 9 hours, compared to 79 days for Iapetus). That means the surface has less time to heat up during the day. Temperatures on Iapetus's bright material are much colder, peaking near 100 Kelvin (-280 Fahrenheit), both because the bright material absorbs less sunlight and because it is further from the equator on this side of Iapetus. Temperatures in the large crater near the center of the disc are slightly different from those in surrounding areas, because sloping surfaces within the crater are warmer where they are tilted towards the Sun and cooler when tilted away from the Sun. The Cassini-Huygens mission is a cooperative project of NASA, the European Space Agency and the Italian Space Agency. The Jet Propulsion Laboratory, a division of the California Institute of Technology in Pasadena, manages the mission for NASA's Science Mission Directorate, Washington, D.C. The Cassini orbiter and its two onboard cameras were designed, developed and assembled at JPL. The composite infrared spectrometer team is based at NASA's Goddard Space Flight Center, Greenbelt, Md. For more information about the Cassini-Huygens mission visit, http://saturn.jpl.nasa.gov and the instrument team's home page, http://cirs.gsfc.nasa.gov/. *Credit*: NASA/JPL/GSFC |
| Date |
January 10, 2005 |
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Iapetus Surface Composition
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Iapetus Surface Composition |
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The Cassini visual and infrared mapping spectrometer analyzed the surface composition of Saturn's moon Iapetus as Cassini flew over the polar region on Dec. 31, 2004. The image at left shows the reflectance at 4-microns, which is dominated by the minerals on Iapetus' surface. Two large craters are seen in this image. The polar water ice is relatively dark at this wavelength, so the ice cap is not seen. The next frame shows carbon dioxide on the surface. The carbon dioxide peaks at mid latitudes and shows less strength at the pole and along the equator (the dark band curving near the left edge of the image). The third frame shows the strength of water absorption on Iapetus. The brightest regions are due to water ice near the pole. The grayer areas indicate water bound to minerals on the surface. The color composite shows water as blue, carbon dioxide as green, and non-ice minerals as red. The Cassini-Huygens mission is a cooperative project of NASA, the European Space Agency and the Italian Space Agency. The Jet Propulsion Laboratory, a division of the California Institute of Technology in Pasadena, manages the mission for NASA's Science Mission Directorate, Washington, D.C. The Cassini orbiter and its two onboard cameras were designed, developed and assembled at JPL. The visible and infrared mapping spectrometer team is based at the University of Arizona, Tucson. For more information about the Cassini-Huygens mission visit, http://saturn.jpl.nasa.gov. For more information about the visual and infrared mapping spectrometer visit http://wwwvims.lpl.arizona.edu/. *Credit*: NASA/JPL/GSFC |
| Date |
January 10, 2005 |
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Iapetus Temperature Variatio
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Iapetus Temperature Variation Map |
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This plot shows how daytime temperatures at low latitudes on the dark material on Saturn's moon Iapetus vary with time of day, from about 130 Kelvin (-226 Fahrenheit) at noon to about 70 Kelvin (-334 Fahrenheit) at sunset. The observations are compared to a "forecast" model (green line) which predicts temperatures based on an assumed value of a parameter called the "thermal inertia. This measures how well the surface can retain heat as conditions change. Rock or solid ice has a high thermal inertia, roughly 2,000,000 as measured in the obscure units used for thermal inertia, meaning that it is good at storing heat and cools down or heats up relatively slowly. On Iapetus, in contrast, temperatures drop precipitously in the afternoon as the Sun sinks towards the horizon, and a very small value of the thermal inertia (30,000 units) is needed in the model to match the data. This means that Iapetus's surface is extremely bad at storing heat, and is thus extremely fluffy, probably due to the pulverizing effect of billions of years of meteorite impacts, though the mysterious process that has darkened this side of Iapetus may also have played a role. The Cassini-Huygens mission is a cooperative project of NASA, the European Space Agency and the Italian Space Agency. The Jet Propulsion Laboratory, a division of the California Institute of Technology in Pasadena, manages the mission for NASA's Science Mission Directorate, Washington, D.C. The Cassini orbiter and its two onboard cameras were designed, developed and assembled at JPL. The composite infrared spectrometer team is based at NASA's Goddard Space Flight Center, Greenbelt, Md. For more information about the Cassini-Huygens mission visit, http://saturn.jpl.nasa.gov and the instrument team's home page, http://cirs.gsfc.nasa.gov/. *Credit*: NASA/JPL/GSFC |
| Date |
January 10, 2005 |
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Enceladus Keeps the Home Fir
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| Description |
Enceladus Keeps the Home Fires Burning |
| Full Description |
On Nov. 9, 2006, Cassini's composite infrared spectrometer captured its first view of the infrared heat radiation emanating from the "tiger stripe" fractures at the south pole of Saturn's moon Enceladus (right) since the discovery of the hot spot 16 months earlier (left). The original discovery was made just before a close flyby of Enceladus on July 14, 2005, and coincided with the discovery of plumes of water-rich gas and ice particles jetting out of the tiger stripes. However, the spacecraft's orbit did not provide any good views of the south pole for follow-up observations until November 2006. The new observations were made from a range of 110,000 kilometers (68,350 miles), slightly more distant than the 80,000-kilometer range (49,700 miles) of the original observations. Comparison of the two images shows that the south polar region continues to be active, and the distribution of temperatures there has changed little in 16 months. The distribution of heat radiation suggests that most or all of the south polar heat comes from the tiger stripes themselves, though the individual stripes are not resolved at the approximate 30-kilometer (19-mile) spatial resolution of these images. The images show the intensity of heat radiation in the 10- to 16-micron wavelength range, translated into temperature and displayed in false color. Peak south polar temperature on both dates reached about 85 Kelvin (minus 306 degrees Fahrenheit), averaged over the 30-kilometer (19-mile) spatial resolution of the data. However, the variation in brightness with wavelength, which is also measured by the composite infrared spectrometer, reveals that the warm region includes small areas, possibly zones a few 100 meters (320 feet) wide along the length of the tiger stripes, that are at higher temperatures, reaching at least 130 Kelvin (minus 225 degrees Fahrenheit) and perhaps much warmer still. While the south polar tiger stripes are almost certainly heated by energy from the moon's interior, daytime regions at low latitudes are warmed by sunlight to temperatures in the high 70s Kelvin (about minus 320 degrees Fahrenheit). The white numbers on the images show west longitudes on Enceladus, which is 500 kilometers (310 miles) in diameter. The dashed line shows the terminator, the boundary between day and night. The blotchy appearance of the cooler regions away from the south pole, and of the sky beyond the globe of Enceladus, is an artifact resulting from the fact that apart from the polar hot spot, the composite infrared spectrometer can barely detect the very faint heat radiation from this very cold moon. The Cassini-Huygens mission is a cooperative project of NASA, the European Space Agency and the Italian Space Agency. The Jet Propulsion Laboratory, a division of the California Institute of Technology in Pasadena, manages the mission for NASA's Science Mission Directorate, Washington, D.C. The Cassini orbiter was designed, developed and assembled at JPL. The, composite infrared spectrometer team is based at NASA's Goddard Space Flight Center, Greenbelt, Md. For more information about the Cassini-Huygens mission visit http://saturn.jpl.nasa.gov/. The composite infrared spectrometer team homepage is http://cirs.gsfc.nasa.gov/. *Image Credit:* NASA/JPL/GSFC/Southwest Research Institute |
| Date |
December 22, 2006 |
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Warm and Dry on Iapetus
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T |
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The imaging operations center is based at the Space Science Institute in Boulder, Colo. For more information about the Cassini-Huygens mission visit http://saturn.jpl.nasa.gov . The composite infrared spectrometer team homepage is http://cirs.gsfc.nasa.gov/. The Cassini imaging team homepage is at http://ciclops.org . Credit: NASA/JPL/GSFC/SwRI/SSI, This image compares midday temperatures on Saturn's moon Iapetus, recorded by the composite infrared spectrometer instrument during Cassini's close Sept. 10, 2007 flyby, with images of the same region recorded during the same flyby by the Cassini imaging science subsystem, shown on the right. See The Other Side of Iapetus for full imaging mosaic. Smallest features visible in the composite infrared spectrometer image (on the left) are about 8 kilometers (5 miles) across. The red rectangle on the visible light (right) image shows the region covered by infrared spectrometer, which extends a distance of 385 kilometers (240 miles) from 36 north, 212 west to 22 south, 220 west. The composite infrared spectrometer determined surface temperatures by measuring the spectrum of infrared radiation emitted by Iapetus in the 9 to 16 micron wavelength range. The dark regions are warmer because they absorb more of the sunlight shining on Iapetus, so dark spots in the visible (right) image show up as warm spots in the infrared image on the left. Temperatures near the equator vary between about 128 Kelvin (minus 229 degrees Fahrenheit) in the darkest regions and about 113 Kelvin (minus 256 degrees Fahrenheit) in the brightest regions. This relatively small temperature difference has a large effect on Iapetus, because at the temperature of the dark regions, a large amount of water ice, which is abundant on most moon surfaces in the Saturn system, can be lost by evaporation over the several-billion year age of Iapetus' surface. Composite infrared spectrometer scientists calculate that when daytime temperatures reach 128 Kelvin (minus 229 degrees Fahrenheit), about 20 meters (65 feet) of ice can be lost per billion years. In the bright regions, with peak temperatures of 113 Kelvin (minus 256 degrees Fahrenheit), only about 10 centimeters, or 2.5 inches, of ice is lost in the same period. It is thus likely that the ice has evaporated completely from the surface of the dark regions of Iapetus, darkening them further, and has collected in the neighboring bright regions, making them brighter, thereby exaggerating initially modest brightness variations. This process is known as thermal segregation. Models by the composite infrared spectrometer team also show that ice evaporated from the warm dark terrain at low latitudes can collect at higher latitudes, and can thus explain the bright polar caps on the dark leading side of Iapetus as well as the relatively dark equatorial regions on the bright trailing side. The Cassini-Huygens mission is a cooperative project of NASA, the European Space Agency and the Italian Space Agency. The Jet Propulsion Laboratory, a division of the California Institute of Technology in Pasadena, manages the mission for NASA's Science Mission Directorate, Washington, D.C. The Cassini orbiter was designed, developed and assembled at JPL. The composite infrared spectrometer team is based at NASA's Goddard Space Flight Center, Greenbelt, Md. |
| Date |
October 8, 2007 |
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Saturn's Rings, Cold and Col
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| Description |
Here on the Gallery page you can find the very latest images, videos and products from the Cassini-Huygens mission to Saturn, including the spectacular launch, spacecraft assembly and the exciting trip to Saturn. |
| Full Description |
The varying temperatures of Saturn's rings are depicted here in this false-color image from the Cassini spacecraft. This image represents the most detailed look to date at the temperature of Saturn's rings. The image was made from data taken by Cassini's composite infrared spectrometer instrument. Red represents temperatures of about 110 Kelvin (-261 degrees Fahrenheit), and blue 70 Kelvin (-333 degrees Fahrenheit). Green is equivalent to 90 Kelvin (-298 degrees Fahrenheit). Water freezes at 273 Kelvin (32 degrees Fahrenheit). The spatial resolution of the ring portion of the image is 200 kilometers (124 miles). The data show that the opaque region of the rings, like the outer A ring (on the far right) and the middle B ring, are cooler, while more transparent sections, like the Cassini Division (in red just inside the A ring) or the inner C ring (shown in yellow and red), are relatively warmer. The temperature data were taken on July 1, 2004, of the unlit side of the rings. In order to show the full breadth of the rings, a strip of temperature data was mapped onto a picture of the lit side of the rings taken with the Cassini narrow angle camera on May 11, 2004, a little over a month before Saturn orbit insertion. Cassini is too close to the planet and hence no pictures of the unlit side of the rings are available, so the temperature data were mapped onto a picture of the lit side of rings. Saturn is overexposed and pure white in this picture. Saturn's moon Enceladus is visible below the rings, toward the center. The original picture and caption are available at http://photojournal.jpl.nasa.gov/catalog/PIA05410. The Cassini-Huygens mission is a cooperative project of NASA, the European Space Agency and the Italian Space Agency. The Jet Propulsion Laboratory, a division of the California Institute of Technology in Pasadena, manages the Cassini-Huygens mission for NASA's Science and Mission Directorate, Washington, D.C. The Cassini orbiter was designed, developed and assembled at JPL. The Composite Infrared Spectrometer team is based at NASA's Goddard Space Flight Center, Greenbelt, Md. For more information about the Cassini-Huygens mission, visit http://saturn.jpl.nasa.gov and the instrument team's home page, http://cirs.gsfc.nasa.gov . Image Credit: NASA/JPL/GSFC/Ames |
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Saturn's Rings, Cold and Col
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| Description |
Here on the Gallery page you can find the very latest images, videos and products from the Cassini-Huygens mission to Saturn, including the spectacular launch, spacecraft assembly and the exciting trip to Saturn. |
| Full Description |
The varying temperatures of Saturn's rings are depicted here in this false-color image from the Cassini spacecraft. This image represents the most detailed look to date at the temperature of Saturn's rings. The image was made from data taken by Cassini's composite infrared spectrometer instrument. Red represents temperatures of about 110 Kelvin (-261 degrees Fahrenheit), and blue 70 Kelvin (-333 degrees Fahrenheit). Green is equivalent to 90 Kelvin (-298 degrees Fahrenheit). Water freezes at 273 Kelvin (32 degrees Fahrenheit). The spatial resolution of the ring portion of the image is 200 kilometers (124 miles). The data show that the opaque region of the rings, like the outer A ring (on the far right) and the middle B ring, are cooler, while more transparent sections, like the Cassini Division (in red just inside the A ring) or the inner C ring (shown in yellow and red), are relatively warmer. The temperature data were taken on July 1, 2004, of the unlit side of the rings. In order to show the full breadth of the rings, a strip of temperature data was mapped onto a picture of the lit side of the rings taken with the Cassini narrow angle camera on May 11, 2004, a little over a month before Saturn orbit insertion. Cassini is too close to the planet and hence no pictures of the unlit side of the rings are available, so the temperature data were mapped onto a picture of the lit side of rings. Saturn is overexposed and pure white in this picture. Saturn's moon Enceladus is visible below the rings, toward the center. The original picture and caption are available at http://photojournal.jpl.nasa.gov/catalog/PIA05410. The Cassini-Huygens mission is a cooperative project of NASA, the European Space Agency and the Italian Space Agency. The Jet Propulsion Laboratory, a division of the California Institute of Technology in Pasadena, manages the Cassini-Huygens mission for NASA's Science and Mission Directorate, Washington, D.C. The Cassini orbiter was designed, developed and assembled at JPL. The Composite Infrared Spectrometer team is based at NASA's Goddard Space Flight Center, Greenbelt, Md. For more information about the Cassini-Huygens mission, visit http://saturn.jpl.nasa.gov and the instrument team's home page, http://cirs.gsfc.nasa.gov . Image Credit: NASA/JPL/GSFC/Ames |
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Warm Fractures on Enceladus
| Description |
Warm Fractures on Enceladus |
| Full Description |
This image shows the warmest places in the south polar region of Saturn's moon Enceladus. The unexpected temperatures were discovered by Cassini's composite infrared spectrometer during a close flyby on July 14, 2005. The image shows how these temperatures correspond to the prominent, bluish fractures dubbed "tiger stripes," first imaged by Cassini's imaging science subsystem cameras. Working together the two teams were able to pinpoint the exact location of the warmest regions on Enceladus. The composite infrared spectrometer instrument measured the infrared heat radiation from the surface at wavelengths between 9 and 16.5 microns within each of the 10 squares shown here. Each square is 6 kilometers (4 miles) across. The color of each square, and the number shown above it, describe the composite infrared spectrometer's measurement of the approximate average temperature of the surface within that square. The warmest temperature squares, at 91 and 89 degrees Kelvin (minus 296 and minus 299 degrees Fahrenheit), are located over one of the "tiger stripe" fractures. They contrast sharply with the surrounding temperatures, which are in the range 74 to 81 degrees Kelvin (minus 326 to minus 313 degrees Fahrenheit). The detailed composite infrared spectrometer data suggest that small areas near the fracture are at substantially higher temperatures, well over 100 degrees Kelvin (minus 279 degrees Fahrenheit). Such "warm" temperatures are unlikely to be due to heating of the surface by the feeble sunlight striking Enceladus' south pole. They are a strong indication that internal heat is leaking out of Enceladus and warming the surface along these fractures. Evaporation of this relatively warm ice probably generates the cloud of water vapor detected above Enceladus' south pole by several other Cassini instruments. Scientists are unsure how the internal heat reaches the surface. The process might involve liquid water, slushy brine, or soft but solid ice. The imaging science subsystem image is an enhanced color view with a pixel scale of 122 meters (400 feet) that was acquired at the same time as the composite infrared spectrometer data. It covers a region 125 kilometers (75 miles) across. The spacecraft's distance from Enceladus was 21,000 kilometers (13,000 miles). The broad bluer fractures that can be seen running from the upper left to the lower right of the image are 1 to 2 kilometers (0.6 to 1.2 miles) wide and more than 100 kilometers (60 miles) long. The fractures are thought to be bluer than the surrounding surface because coarser-grained ice (which has a blue color just as thick masses of ice, like glaciers and icebergs, do on Earth) has been exposed in the fractures. The color image was constructed using an ultraviolet filter (centered at 338 nanometers) in the blue channel, a clear filter in the green channel, and an infrared filter (centered at 930 nanometers) in the red channel. The Cassini-Huygens mission is a cooperative project of NASA,, the European Space Agency and the Italian Space Agency. The Jet Propulsion Laboratory, a division of the California Institute of Technology in Pasadena, manages the mission for NASA's Science Mission Directorate, Washington, D.C. The Cassini orbiter was designed, developed and assembled at JPL. The composite infrared spectrometer team is based at NASA's Goddard Space Flight Center, Greenbelt, Md. The imaging operations center is based at the Space Science Institute in Boulder, Colo. For more information about the Cassini-Huygens mission visit http://saturn.jpl.nasa.gov . The composite infrared spectrometer team homepage is http://cirs.gsfc.nasa.gov/ . The imaging team homepage is at http://ciclops.org . Credit: NASA/JPL/GSFC/Space Science Institute |
| Date |
July 29, 2005 |
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Enceladus Temperature Map
| Description |
Enceladus Temperature Map |
| Full Description |
This image shows the surprise that startled Cassini scientists on the composite infrared spectrometer team when they got their first look at the infrared (heat) radiation from the south pole of Saturn's moon Enceladus. There is a dramatic warm spot centered on the pole that is probably a sign of internal heat leaking out of the icy moon. The data were taken during the spacecraft's third flyby of this intriguing moon on July 14, 2005. Based on data from previous flybys, which did not show the south pole well, team members expected that the south pole would be very cold, as shown in the left panel. Enceladus is one of the coldest places in the Saturn system because its extremely bright surface reflects 80 percent of the sunlight that hits it, so only 20 percent is available to heat the surface. As on Earth, the poles should be even colder than the equator because the sun shines at such an oblique angle there. The right hand panel shows a global temperature image made from measurements of Enceladus' heat radiation at wavelengths between 9 and 16.5 microns. Cassini made the observation from a distance of 84,000 kilometers (52,000 miles) on the approach to Enceladus, and the image shows details as small as 25 kilometers (16 miles). Equatorial temperatures are much as expected, topping out at about 80 degrees Kelvin (-315 degrees Fahrenheit), but the south pole is occupied by a well-defined warm region reaching 85 Kelvin (-305 degrees Fahrenheit). That is 15 degrees Kelvin (27 degrees Fahrenheit) warmer than expected. The composite infrared spectrometer data further suggest that small areas of the pole are at even higher temperatures, well over 110 degrees Kelvin (-261 degrees Fahrenheit). Evaporation of this relatively warm ice probably generates the cloud of water vapor detected above Enceladus' south pole by several other Cassini instruments. The south polar temperatures are very difficult to explain if sunlight is the only energy source heating the surface, though exotic sunlight-trapping mechanisms have not yet been completely ruled out. It therefore seems likely that portions of the polar region are warmed by heat escaping from the interior of the moon. This would make Enceladus only the third solid body in the solar system, after Earth and Jupiter's volcanic moon Io, where hot spots powered by internal heat have been detected. The Cassini-Huygens mission is a cooperative project of NASA, the European Space Agency and the Italian Space Agency. The Jet Propulsion Laboratory, a division of the California Institute of Technology in Pasadena, manages the mission for NASA's Science Mission Directorate, Washington, D.C. The Cassini orbiter was designed, developed and assembled at JPL. The composite infrared spectrometer team is based at NASA's Goddard Space Flight Center, Greenbelt, Md. For more information about the Cassini-Huygens mission visit http://saturn.jpl.nasa.gov . The composite infrared spectrometer team homepage is, http://cirs.gsfc.nasa.gov/ . Credit: NASA/JPL/GSFC |
| Date |
July 29, 2005 |
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Phoebe's Radiation
| Description |
Phoebe's Radiation |
| Full Description |
This image shows thermal radiation from the day and night sides of Saturn's moon Phoebe, taken by the composite infrared spectrometer onboard Cassini 1.8 hours before the spacecraft's closest approach to Phoebe on June 11, 2004. The left-hand panel displays the image in grayscale format, showing the brightness of Phoebe's radiation in the wavelength range 15-17 microns, which is about 25 times the longest wavelength visible to the naked eye. In the middle panel this brightness is used to estimate the surface temperature distribution across Phoebe. Temperatures are given in degrees Kelvin, and vary from a relatively toasty 107 Kelvin (-267 Fahrenheit), in the late morning near the equator (white, lower right), to less than 75 Kelvin (-324 Fahrenheit) in the northern hemisphere in the pre-dawn hours (dark blue, upper left). The "ragged edge" of Phoebe in this region is an instrumental artifact. Temperatures are affected strongly by topography, as can be seen by comparison with the visible-wavelength image (right). Some of the coldest temperatures are found in the shadowed region inside the large depression in the northern hemisphere (upper right). The Cassini-Huygens mission is a cooperative project of NASA, the European Space Agency and the Italian Space Agency. The Jet Propulsion Laboratory, a division of the California Institute of Technology in Pasadena, manages the Cassini-Huygens mission for NASA's Office of Space Science, Washington, D.C. The Cassini orbiter and its two onboard cameras were designed, developed and assembled at JPL. The composite infrared spectrometer team is based at NASA's Goddard Space Flight Center, Greenbelt, Md. For more information about the Cassini-Huygens mission, visit http://saturn.jpl.nasa.gov and the Cassini composite infrared spectrometer home page at http://cirs.gsfc.nasa.gov/ . Image Credit: NASA/JPL/Goddard Space Flight Center |
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Atlas Found!
| Description |
Here on the Gallery page you can find the very latest images, videos and products from the Cassini-Huygens mission to Saturn, including the spectacular launch, spacecraft assembly and the exciting trip to Saturn. |
| Full Description |
The Cassini spacecraft has sighted the tiny moon Atlas, which is seen here for the first time since Voyager 1 flew past Saturn in 1980. Cassini's narrow angle camera captured a sequence of 112 images in visible light, which were used to create a movie of Atlas and other moons racing around the outer edge of Saturn's rings. One of those images is shown here. Over the course of almost five and one-quarter hours, Cassini watched the moons as they circled the planet, snapping 1.2-second exposures about 12 minutes apart. These images were part of a sequence designed specifically to search for small moons near Saturn's F ring. Contrast was enhanced in the images, and the rings themselves were overexposed intentionally, to make these small moons visible. A group of three moons can be seen rounding the right loop of Saturn's rings, followed by a fourth moon. In the first group, the moon exterior to Saturn's thin, knotted F ring is Epimetheus (116 kilometers, 72 miles across), the two moons interior to the F ring are Prometheus (102 kilometers, 63 miles across) and tiny unresolved Atlas (32 kilometers, 20 miles across). The fourth moon seen here, exterior to the F ring and tagging along behind the others, is Pandora (84 kilometers, 52 miles across). At the same time, on the left side, Janus can be seen (181 kilometers, 113 miles across). The view is taken looking upward from Cassini's southern vantage point beneath the ring plane. The moons visible here are orbiting Saturn in a plane that is tilted 67 degrees away from the viewer. These images were taken on May 26 and 27, 2004, from a distance of approximately 19.2 million kilometers (11.9 million miles) from Saturn. The image scale is approximately 114 kilometers (71 miles) per pixel. The Cassini-Huygens mission is a cooperative project of NASA, the European Space Agency and the Italian Space Agency. The Jet Propulsion Laboratory, a division of the California Institute of Technology in Pasadena, manages the Cassini-Huygens mission for NASA's Office of Space Science, Washington, D.C. The Cassini orbiter and its two onboard cameras were designed, developed and assembled at JPL. The imaging team is based at the Space Science Institute, Boulder, Colo. For more information about the Cassini-Huygens mission, visit http://saturn.jpl.nasa.gov and the Cassini imaging team home page, http://ciclops.org . Image Credit: NASA/JPL/Goddard Space Flight Center |
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Phoebe Temperature Maps
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Phoebe Temperature Maps |
| Full Description |
A montage of maps of Saturn's moon Phoebe shows surface temperatures at various times of day as determined by the composite infrared spectrometer onboard Cassini during the June 11, 2004, Phoebe flyby. The asterisk on each map shows the location of the subsolar point, where the Sun is directly overhead. This point moves across the surface as Phoebe rotates. It is morning in regions to the left of the subsolar point, and afternoon in regions to the right. Like a newspaper weather map, different colors indicate different temperatures, though Phoebe's temperatures are distinctly cooler than even the coldest January day on Earth. Equatorial temperatures peak in the early afternoon near 112 Kelvin (-257 Fahrenheit), plunging to 78 Kelvin (-319 Fahrenheit) before dawn, and are even colder at higher latitudes. The large day/night temperature contrasts imply that Phoebe's surface is covered in loose dust or ice particles that store little heat and thus cool off rapidly at night. Regions of Phoebe's surface that were not observed are shown in black. Most of the maps show the effect on surface temperatures of the large crater-like depression seen in Cassini's visible-wavelength images of Phoebe, which is located just left of center in these maps. Crater walls that are shadowed and cold in the early morning in the first map are sunlit and warm in the late afternoon in the final map. The Cassini-Huygens mission is a cooperative project of NASA, the European Space Agency and the Italian Space Agency. The Jet Propulsion Laboratory, a division of the California Institute of Technology in Pasadena, manages the Cassini-Huygens mission for NASA's Office of Space Science, Washington, D.C. The Cassini orbiter was designed, developed and assembled at JPL. The composite infrared spectrometer team is based at NASA's Goddard Space Flight Center, Greenbelt, Md. For more information about the Cassini-Huygens mission, visit http://saturn.jpl.nasa.gov and the Cassini composite infrared spectrometer home page at http://cirs.gsfc.nasa.gov/ . Image Credit: NASA/JPL/Goddard Space Flight Center |
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Iapetus Temperature Map
| Description |
Iapetus Temperature Map |
| Full Description |
This temperature map of Saturn's moon Iapetus is constructed from observations of Iapetus's infrared heat radiation taken with the Cassini composite infrared spectrometer instrument during the Dec. 31, 2004 flyby. The orange asterisk marks the point on Iapetus where the Sun is directly overhead. Temperatures reach nearly 130 Kelvin (-226 Fahrenheit) at noon on the equator on the dark material that covers most of this side of Iapetus, making high noon on Iapetus's dark side probably the warmest places in the Saturn system. This is much warmer than temperatures on the moon Phoebe measured by the composite infrared spectrometer in June 2004, which peaked near 112 Kelvin (-258 Fahrenheit). That's because, although Phoebe is almost as dark as Iapetus's dark material and absorbs nearly as much sunlight, Phoebe rotates much more quickly (once every 9 hours, compared to 79 days for Iapetus). That means the surface has less time to heat up during the day. Temperatures on Iapetus' bright material are much colder, peaking near 100 Kelvin (-280 Fahrenheit), both because the bright material absorbs less sunlight and because it is further from the equator on this side of Iapetus. The Cassini-Huygens mission is a cooperative project of NASA, the European Space Agency and the Italian Space Agency. The Jet Propulsion Laboratory, a division of the California Institute of Technology in Pasadena, manages the mission for NASA's Science Mission Directorate, Washington, D.C. The Cassini orbiter and its two onboard cameras were designed, developed and assembled at JPL. The composite infrared spectrometer team is based at NASA's Goddard Space Flight Center, Greenbelt, Md. For more information about the Cassini-Huygens mission visit, http://saturn.jpl.nasa.gov and the instrument team's home page, http://cirs.gsfc.nasa.gov/. *Credit*: NASA/JPL/GSFC |
| Date |
January 10, 2005 |
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Searching for Warmth
| Description |
The exciting mystery of an active south polar region on Saturn's icy moon Enceladus continues to unfold as scientists make the correlation between geologically youthful surface fractures and unusually warm temperatures. |
| Full Description |
The exciting mystery of an active south polar region on Saturn's icy moon Enceladus continues to unfold as scientists make the correlation between geologically youthful surface fractures and unusually warm temperatures. This view shows excess heat radiation from cracks near the moon's south pole. These warm fissures are the source of plumes of dust and gas seen by multiple instruments on the Cassini spacecraft during its flyby of Enceladus on July 14, 2005, as described in a series of papers in the March 10, 2006, issue of the journal Science. This image shows two arrays of temperature readings across the surface of Enceladus, as measured by the Cassini composite infrared spectrometer, superimposed on images of the surface taken simultaneously by the imaging science subsystem. Surface temperatures in Kelvin, derived from the intensity of infrared radiation detected by the composite infrared spectrometer, are shown along with their formal uncertainties, although true uncertainties for temperatures below about 75 Kelvin (minus 325 degrees Fahrenheit) are not easily described by a single number. Enhanced thermal emission is seen in the vicinity of the prominent "tiger stripe" fissures discovered by the imaging cameras. In this image, the excess emission is most strongly seen in the left-most composite infrared spectrometer field of view, which includes a fissure near the end of one of the tiger stripes. The peak temperatures, 86 Kelvin and 90 Kelvin (minus 305 and minus 298 degrees Fahrenheit) respectively, are averages over the composite infrared spectrometer field of view, and other composite infrared spectrometer data suggest that much higher temperatures, up to at least 145 Kelvin (minus 199 degrees Fahrenheit), occur in narrow zones a few hundred meters wide along the tiger stripe fissures. See (PIA07794) for a related image. This image is centered near longitude 135 west, latitude 65 south, and each square from the composite infrared spectrometer field of view is 17.5 kilometers (10.9 miles) across. This Cassini narrow-angle camera image has been cropped and resized for presentation. The Cassini-Huygens mission is a cooperative project of NASA, the European Space Agency and the Italian Space Agency. The Jet Propulsion Laboratory, a division of the California Institute of Technology in Pasadena, manages the mission for NASA's Science Mission Directorate, Washington, D.C. The Cassini orbiter was designed, developed and assembled at JPL. The composite infrared spectrometer team is based at NASA's Goddard Space Flight Center, Greenbelt, Md. The imaging operations center is based at the Space Science Institute in Boulder, Colo. For more information about the Cassini-Huygens mission visit http://saturn.jpl.nasa.gov. The composite infrared spectrometer team homepage is http://cirs.gsfc.nasa.gov/. The imaging team homepage is at http://ciclops.org *Credit:* NASA/JPL/GSFC/Space Science Institute |
| Date |
March 9, 2006 |
|
Searching for Warmth
| Description |
The exciting mystery of an active south polar region on Saturn's icy moon Enceladus continues to unfold as scientists make the correlation between geologically youthful surface fractures and unusually warm temperatures. |
| Full Description |
The exciting mystery of an active south polar region on Saturn's icy moon Enceladus continues to unfold as scientists make the correlation between geologically youthful surface fractures and unusually warm temperatures. This view shows excess heat radiation from cracks near the moon's south pole. These warm fissures are the source of plumes of dust and gas seen by multiple instruments on the Cassini spacecraft during its flyby of Enceladus on July 14, 2005, as described in a series of papers in the March 10, 2006, issue of the journal Science. This image shows two arrays of temperature readings across the surface of Enceladus, as measured by the Cassini composite infrared spectrometer, superimposed on images of the surface taken simultaneously by the imaging science subsystem. Surface temperatures in Kelvin, derived from the intensity of infrared radiation detected by composite infrared spectrometer, are shown along with their formal uncertainties, although true uncertainties for temperatures below about 75 Kelvin (minus 325 degrees Fahrenheit) are not easily described by a single number. Enhanced thermal emission is seen in the vicinity of the prominent "tiger stripe" fissures discovered by the imaging cameras. In this image, the excess emission is near the center of the composite infrared spectrometer array, directly over a tiger stripe fissure. The peak temperatures, 86 Kelvin and 90 Kelvin (minus 305 and minus 298 degrees Fahrenheit) respectively, are averages over the composite infrared spectrometer field of view, and other composite and infrared spectrometer data suggest that much higher temperatures, up to at least 145 Kelvin (minus 199 degrees Fahrenheit), occur in narrow zones a few hundred meters wide along the tiger stripe fissures. See (PIA07793) for a related image. This image was taken nearly three times closer to the moon and is centered near longitude 120 west, latitude 82 south, and each composite infrared spectrometer field of view is 6.0 kilometers (3.7 miles) across. This Cassini narrow-angle camera image was cropped and resized for presentation. The Cassini-Huygens mission is a cooperative project of NASA, the European Space Agency and the Italian Space Agency. The Jet Propulsion Laboratory, a division of the California Institute of Technology in Pasadena, manages the mission for NASA's Science Mission Directorate, Washington, D.C. The Cassini orbiter was designed, developed and assembled at JPL. The composite infrared spectrometer team is based at NASA's Goddard Space Flight Center, Greenbelt, Md. The imaging operations center is based at the Space Science Institute in Boulder, Colo. For more information about the Cassini-Huygens mission visit http://saturn.jpl.nasa.gov. The composite infrared spectrometer team homepage is http://cirs.gsfc.nasa.gov/. The imaging team homepage is at http://ciclops.org *Credit:* NASA/JPL/GSFC/Space Science Institute |
| Date |
March 9, 2006 |
|
The Secret Lives of Galaxies
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| Title |
The Secret Lives of Galaxies Unveiled in Deep Survey |
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The Secret Lives of Galaxies
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| Title |
The Secret Lives of Galaxies Unveiled in Deep Survey |
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NASA's Hubble Looks for Poss
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| Title |
NASA's Hubble Looks for Possible Moon Resources |
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Cassiopeia A - The Colorful
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| Title |
Cassiopeia A - The Colorful Aftermath of a Violent Stellar Death |
| General Information |
What is Hubble Heritage? A monthly showcase of new and archival Hubble images. Go to the Heritage site. A new image taken with NASA's Hubble Space Telescope provides a detailed look at the tattered remains of a supernova explosion known as Cassiopeia A (Cas A). It is the youngest known remnant from a supernova explosion in the Milky Way. The new Hubble image shows the complex and intricate structure of the star's shattered fragments. The image is a composite made from 18 separate images taken in December 2004 using Hubble's Advanced Camera for Surveys (ACS). |
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Spitzer and Hubble Capture E
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| Title |
Spitzer and Hubble Capture Evolving Planetary Systems |
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The Carina Nebula: Star Birt
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| Title |
The Carina Nebula: Star Birth in the Extreme |
| General Information |
What is Hubble Heritage? A monthly showcase of new and archival Hubble images. Go to the Heritage site. In celebration of the 17th anniversary of the launch and deployment of NASA's Hubble Space Telescope, a team of astronomers is releasing one of the largest panoramic images ever taken with Hubble's cameras. READ: Junior version of this article Amazing Space Learn about this story in the Star Witness, a science newspaper available on our sister site, Amazing Space. [ http://amazing-space.stsci.edu/news/archive/2007/02/ ] It is a 50-light-year-wide view of the central region of the Carina Nebula where a maelstrom of star birth —, and death —, is taking place. This image is a mosaic of the Carina Nebula assembled from 48 frames taken with Hubble's Advanced Camera for Surveys. The Hubble images were taken in the light of neutral hydrogen during March and July 2005. Color information was added with data taken in December 2001 and March 2003 at the Cerro Tololo Inter-American Observatory in Chile. Red corresponds to sulfur, green to hydrogen, and blue to oxygen emission. |
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The Carina Nebula: Star Birt
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| Title |
The Carina Nebula: Star Birth in the Extreme |
| General Information |
What is Hubble Heritage? A monthly showcase of new and archival Hubble images. Go to the Heritage site. In celebration of the 17th anniversary of the launch and deployment of NASA's Hubble Space Telescope, a team of astronomers is releasing one of the largest panoramic images ever taken with Hubble's cameras. READ: Junior version of this article Amazing Space Learn about this story in the Star Witness, a science newspaper available on our sister site, Amazing Space. [ http://amazing-space.stsci.edu/news/archive/2007/02/ ] It is a 50-light-year-wide view of the central region of the Carina Nebula where a maelstrom of star birth —, and death —, is taking place. This image is a mosaic of the Carina Nebula assembled from 48 frames taken with Hubble's Advanced Camera for Surveys. The Hubble images were taken in the light of neutral hydrogen during March and July 2005. Color information was added with data taken in December 2001 and March 2003 at the Cerro Tololo Inter-American Observatory in Chile. Red corresponds to sulfur, green to hydrogen, and blue to oxygen emission. |
|
The Carina Nebula: Star Birt
…
| Title |
The Carina Nebula: Star Birth in the Extreme |
| General Information |
What is Hubble Heritage? A monthly showcase of new and archival Hubble images. Go to the Heritage site. In celebration of the 17th anniversary of the launch and deployment of NASA's Hubble Space Telescope, a team of astronomers is releasing one of the largest panoramic images ever taken with Hubble's cameras. READ: Junior version of this article Amazing Space Learn about this story in the Star Witness, a science newspaper available on our sister site, Amazing Space. [ http://amazing-space.stsci.edu/news/archive/2007/02/ ] It is a 50-light-year-wide view of the central region of the Carina Nebula where a maelstrom of star birth —, and death —, is taking place. This image is a mosaic of the Carina Nebula assembled from 48 frames taken with Hubble's Advanced Camera for Surveys. The Hubble images were taken in the light of neutral hydrogen during March and July 2005. Color information was added with data taken in December 2001 and March 2003 at the Cerro Tololo Inter-American Observatory in Chile. Red corresponds to sulfur, green to hydrogen, and blue to oxygen emission. |
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A Lunar Eclipse in Three Exp
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| Title |
A Lunar Eclipse in Three Exposures |
| Explanation |
Our Moon turned red last week. The reason was that during the night of January 20, a total lunar eclipse [ http://sunearth.gsfc.nasa.gov/eclipse/SEextra/TLE2000Jan20.html ] occurred. The above digitally superimposed photographs captured the Moon [ http://stardate.utexas.edu/resources/ssguide/moon.html ] three times during this lunar eclipse [ http://spacescience.com/headlines/y2000/ast19jan_1.htm ], once just as the Moon entered the Earth's shadow [ http://antwrp.gsfc.nasa.gov/apod/ap990830.html ], once when the Moon was near the middle of the shadow [ http://antwrp.gsfc.nasa.gov/apod/ap951128.html ], and once just before the Moon exited. The red tint of the eclipsed Moon [ http://eclipse.span.ch/liveshow.htm ] is created by sunlight first passing through the Earth's atmosphere, which preferentially scatters blue light (making the sky blue [ http://math.ucr.edu/home/baez/physics/blue_sky.html ]) but passes and refracts [ http://www.treasure-troves.com/physics/Refraction.html ] red light, before reflecting back off the Moon. Differing amounts of clouds [ http://vortex.plymouth.edu/clouds.html ] and volcanic dust [ http://octopus.gma.org/surfing/weather/dust.html ] in the Earth's atmosphere make each lunar eclipse [ http://aa.usno.navy.mil/AA/data/docs/LunarEclipse.html ] appear differently. |
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Super-Earths May Circle Othe
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| Title |
Super-Earths May Circle Other Stars |
| Explanation |
Are "super-Earths" common around other star systems? Quite possibly. Unexpected evidence [ http://www.cfa.harvard.edu/press/pr0614.html ] for this came to light recently when a planet orbiting a distant star gravitationally magnified [ http://astron.berkeley.edu/~jcohn/lens.html ] the light of an even more distant star. Assuming the planet's parent star is normal red dwarf [ http://en.wikipedia.org/wiki/Red_dwarf ], the brightening is best explained if the planet is about 13 times the mass of the Earth [ http://antwrp.gsfc.nasa.gov/apod/ap030324.html ] and orbiting at the distance of the asteroid belt [ http://antwrp.gsfc.nasa.gov/apod/ap060319.html ] in our own Solar System [ http://space.jpl.nasa.gov/ ]. Given the small number of objects observed and similar determinations already obtained for other star systems, these super-Earths might be relatively common. Astronomers speculate [ http://arxiv.org/PS_cache/astro-ph/pdf/0603/0603276.pdf ] that the planet might have grown into a Jupiter-sized [ http://antwrp.gsfc.nasa.gov/apod/ap050911.html ] planet if its star system had more gas. Since the planet was not observed directly, significant uncertainty [ http://www.aip.org/history/heisenberg/p08c.htm ] remains in its defining attributes, and future research will be aimed at better understanding this intriguing system. The above drawing [ http://www.cfa.harvard.edu/press/pr0614image.html ] gives an artist's depiction of what a super-Earth orbiting a distant red dwarf [ http://imagine.gsfc.nasa.gov/docs/science/know_l2/stars.html ] star might look like, complete with a hypothetical moon [ http://antwrp.gsfc.nasa.gov/apod/ap050805.html ]. |
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Three Galaxies in Draco
| Title |
Three Galaxies in Draco |
| Explanation |
This intriguing trio [ http://www.angelfire.com/id/jsredshift/ triplets.htm ] of galaxies is sometimes called the NGC 5985/Draco Group and so (quite reasonably) is located in the northern constellation Draco [ http://en.wikipedia.org/wiki/Draco_(constellation) ]. From left to right are face-on spiral [ http://antwrp.gsfc.nasa.gov/apod/ap040410.html ] NGC 5985, elliptical galaxy [ http://antwrp.gsfc.nasa.gov/apod/ap991121.html ] NGC 5982, and edge-on spiral [ http://antwrp.gsfc.nasa.gov/apod/ap010510.html ] NGC 5981 -- all within this single telescopic field of view spanning a little more than half the width of the full moon. While this grouping is far too small to be a galaxy cluster [ http://www.seds.org/messier/gal_clus.html ] and has not been cataloged [ http://www.astro.ubc.ca/people/hickson/hcg/ ] as a compact group [ http://antwrp.gsfc.nasa.gov/apod/ap990906.html ], these galaxies all do lie roughly 100 million light-years from planet Earth. On close examination with spectrographs [ http://imagine.gsfc.nasa.gov/docs/ science/how_l1/spectral.html ], the bright core of the striking face-on spiral NGC 5985 shows prominent emission in specific wavelengths of light, prompting astronomers to classify it as a Seyfert [ http://www.seds.org/~spider/spider/ScholarX/ seyferts.html ], a type of active galaxy. Not as well known as other tight groupings of galaxies [ http://antwrp.gsfc.nasa.gov/apod/ap050716.html ], the contrast in visual appearance makes this triplet an attractive subject for astrophotographers [ http://home.tiscali.de/heutz_st/ ]. This impressively deep exposure of region also reveals faint and even more distant background galaxies [ http://www.noao.edu/outreach/aop/observers/ bggalaxies.html ]. |
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Descent Panorama of Saturn's
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| Title |
Descent Panorama of Saturn's Titan |
| Explanation |
You're the first spacecraft ever to descend to Titan -- what do you see? Immediately after the Huygen's probe [ http://en.wikipedia.org/wiki/Huygens_probe ] pierced the cloud deck of Saturn [ http://en.wikipedia.org/wiki/Saturn_%28planet%29 ]'s moon Titan [ http://antwrp.gsfc.nasa.gov/cgi-bin/apod/apod_search?titan ] last January, it took a unique series of pictures of one of the Solar System [ http://www.windows.ucar.edu/our_solar_system/solar_system.html ]'s most mysterious moon's. Those pictures have recently been digitally stitched together to create spectacular panoramas and a dramatic descent movie [ http://photojournal.jpl.nasa.gov/catalog/PIA08117 ]. Pictured above [ http://photojournal.jpl.nasa.gov/catalog/PIA08114 ] is a panoramic fisheye view Huygen's obtained from about five kilometers above Titan's surface [ http://antwrp.gsfc.nasa.gov/apod/ap050117.html ]. The digital projection makes the local surface, mostly flat, appear as a ball, but allows one to see in all directions. Huygen's eventual landing site [ http://antwrp.gsfc.nasa.gov/apod/ap050518.html ] was in the large dark area below, just right of the center. This relatively featureless, dark, sandy basin appears to be surrounded by light colored hills to the right and a landscape fractured by streambeds and canyons [ http://antwrp.gsfc.nasa.gov/apod/ap050124.html ] above. Recent evidence [ http://uanews.org/cgi-bin/WebObjects/UANews.woa/16/wa/MainStoryDetails?ArticleID=12614 ] indicates that Titan's lakebeds and streambeds are usually dry but sometimes filled with a flashflood of liquid methane [ http://en.wikipedia.org/wiki/Methane ] from rare torrents of methane rain [ http://www.astrobio.net/news/article1413.html ]. |
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Simulated Gamma-ray Sky
| Title |
Simulated Gamma-ray Sky |
| Explanation |
Scheduled for launch in 2007, the Gamma-ray Large Area Space Telescope [ http://glast.gsfc.nasa.gov/public/ ] (GLAST) will explore the Universe in gamma-rays [ http://cossc.gsfc.nasa.gov/docs/cgro/epo/vu/ index.html ], the most energetic form of light. To get ready, consider this dynamic gamma-ray sky animation - constructed from simulating the first 55 days (seen above at one frame per day) of GLAST observations of cosmic gamma-ray sources. The all-sky view is projected in an astronomical (RA-Dec) coordinate [ http://www.astronomynotes.com/nakedeye/s6.htm ] system that shows the plane of our Milky Way Galaxy as a broad U-shape, with the center of the galaxy toward the right. So what shines in this gamma-ray sky [ http://antwrp.gsfc.nasa.gov/apod/ap020112.html ]? Besides the diffuse Milky Way glow, astronomers testing their skills on the simulated data have found flaring active galaxies [ http://imagine.gsfc.nasa.gov/docs/science/know_l2/ active_galaxies.html ], pulsars [ http://antwrp.gsfc.nasa.gov/apod/ap010602.html ], gamma-ray bursts [ http://www.pbs.org/wgbh/nova/gamma/milkyway.html ], the flaring Sun [ http://hesperia.gsfc.nasa.gov/hessi/flares.htm ], and of course, the gamma-ray Moon [ http://antwrp.gsfc.nasa.gov/apod/ap060527.html ]. |
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Gamma-Ray Moon
| Title |
Gamma-Ray Moon |
| Explanation |
If you could see gamma rays [ http://antwrp.gsfc.nasa.gov/apod/ap000722.html ] - photons with a million or more times the energy of visible light - the Moon would appear brighter than the Sun! The startling notion is demonstrated by this image of the Moon from the Energetic Gamma Ray Experiment Telescope (EGRET [ http://cossc.gsfc.nasa.gov/docs/cgro/cgro/egret.html ]) in orbit on NASA's Compton Gamma Ray Observatory [ http://cossc.gsfc.nasa.gov/docs/cgro/index.html ] from April 1991 to June 2000. Then, the most sensitive instrument of its kind, even EGRET could not see the quiet Sun which is extremely faint at gamma-ray energies. So why [ http://www.aas.org/publications/baas/v28n4/aas189/abs/ S025002.html ] is the Moon bright? High energy charged particles, known as cosmic rays [ http://imagine.gsfc.nasa.gov/docs/features/topics/snr_group/ cosmic_rays.html ], constantly bombard the unprotected lunar surface generating gamma-ray photons. EGRET's gamma-ray vision [ http://cossc.gsfc.nasa.gov/docs/cgro/epo/vu/ index.html ] was not sharp enough to resolve a lunar disk or any surface features, but its sensitivity reveals the induced gamma-ray [ http://antwrp.gsfc.nasa.gov/apod/ap050331.html ] moonglow. So far unique [ http://glast.gsfc.nasa.gov/ ], the image was generated from eight exposures made during 1991-1994 and covers a roughly 40 degree wide field of view with gamma-ray intensity represented in false color. |
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Ultraviolet Earth from the M
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| Title |
Ultraviolet Earth from the Moon |
| Explanation |
Here's a switch: the above picture is of the " Earth " taken from a " lunar " observatory! [ http://antwrp.gsfc.nasa.gov/apod/ap960608.html ] This false color picture [ http://images.jsc.nasa.gov/images/pao/AS16/10075878.htm ] shows how the Earth [ http://antwrp.gsfc.nasa.gov/apod/earth.html ] glows in ultraviolet [ http://antwrp.gsfc.nasa.gov/apod/lib/glossary.html#uv ] (UV) light. UV light is so blue humans can't see it. Very little UV light [ http://titan.srrb.noaa.gov/UV/ ] is transmitted through the Earth's atmosphere but what sunlight does make it through can cause a sunburn [ http://uhs.bsd.uchicago.edu/uhs/infoline/sunburn.htm ]. The Far UV Camera / Spectrograph [ http://cass.jsc.nasa.gov/pub/expmoon/Apollo16/A16_Experiments_UVC.html ] deployed and left on the Moon by the crew of Apollo 16 [ http://antwrp.gsfc.nasa.gov/apod/ap000319.html ] took the above picture. The part of the Earth facing the Sun [ http://antwrp.gsfc.nasa.gov/apod/sun.html ] reflects much UV light, but perhaps more interesting is the side facing away from the Sun. Here bands of UV emission [ http://imagine.gsfc.nasa.gov/docs/science/know_l2/emspectrum.html ] are also apparent. These bands [ http://antwrp.gsfc.nasa.gov/apod/ap970402.html ] are the result of aurorae [ http://antwrp.gsfc.nasa.gov/cgi-bin/apod/apod_ts?aurora ] and are caused by charged particles [ http://www-spof.gsfc.nasa.gov/Education/Intro.html ] expelled by the Sun. |
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Moon And Venus Share The Sky
| Title |
Moon And Venus Share The Sky |
| Explanation |
July is drawing to a close and in the past few days, some early morning risers [ http://antwrp.gsfc.nasa.gov/apod/ap990714.html ] could have looked east and seen a crescent Moon sharing the pre-dawn [ http://science.nasa.gov/headlines/y2000/ast25jul_1m.htm ] skies with planets Jupiter and Saturn. Planet Mercury will also pass about 2 degrees from the thin waning crescent Moon [ http://aa.usno.navy.mil/AA/faq/docs/moon_phases.html ] just before sunrise near the eastern horizon on Saturday, July 29. And finally, on the evening of July 31st, Venus will take its turn near the crescent Moon [ http://antwrp.gsfc.nasa.gov/apod/ap991108.html ]. But this time it will be a day-old crescent Moon near the western horizon, shortly after sunset [ http://antwrp.gsfc.nasa.gov/apod/ap000507.html ]. In fact [ http://pages.prodigy.net/pam.orman/JoeAlmanac2000.html ], on July 31 (August 1 Universal Time) the Moon will occult [ http://www.skypub.com/sights/occultations/lunar/ 0001lunarocc.html ] (pass in front of) Venus for northwestern observers [ http://www.skypub.com/sights/images2000/ 0008moonvenus_big.jpg ] in North America. This telescopic picture taken on 31 December 1997, shows a lovely young crescent Moon and brilliant crescent Venus in [ http://antwrp.gsfc.nasa.gov/apod/ap990903.html ] the early evening sky near Bursa, Turkey [ http://www.mersina.com/Turkey/Marmara/Bursa/index.html ]. And what about the Sun? On Sunday, July 30, a partial eclipse of the Sun [ http://sunearth.gsfc.nasa.gov/eclipse/extra/ PSE2000Jul31.html ] will be visible from some locations [ http://sunearth.gsfc.nasa.gov/eclipse/OH/ PSE2000Jul.gif ] in North America. |
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NGC 6960: The Witch's Broom
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| Title |
NGC 6960: The Witch's Broom Nebula |
| Explanation |
Ten thousand years ago, before the dawn of recorded human history [ http://news.bbc.co.uk/hi/english/sci/tech/newsid_334000/334517.stm ], a new light must suddenly have appeared in the night sky and faded after a few weeks. Today we know this light was an exploding star [ http://imagine.gsfc.nasa.gov/docs/science/know_l1/supernovae.html ] and record the colorful expanding cloud as the Veil Nebula [ http://nineplanets.org/twn/cygnusx.html ]. Pictured above [ http://robgendler.astrodigitals.com/Nebulas.html ] is the west end of the Veil Nebula [ http://www.astropix.com/HTML/E_SUM_N/VEIL.HTM ] known technically as NGC [ http://www.ngcic.com/dss/dss_images.htm ] 6960 but less formally as the Witch's Broom Nebula. The rampaging gas gains its colors by impacting and exciting existing [ http://antwrp.gsfc.nasa.gov/apod/ap960307.html ] nearby gas. The supernova remnant [ http://antwrp.gsfc.nasa.gov/apod/supernova_remnants.html ] lies about 1400 light-years away towards the constellation of Cygnus [ http://www.multimania.com/cdadfs/constellation/cygne/cygnus.htm ]. This Witch's Broom actually spans over three times the angular size of the full Moon [ http://antwrp.gsfc.nasa.gov/apod/moon.html ]. The bright blue star 52 Cygnus [ http://www.seds.org/Maps/Stars_en/Fig/cygnus.html ] is visible with the unaided eye from a dark location but unrelated to the ancient supernova [ http://www.chapman.edu/oca/benet/intro_sn.htm ]. |
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X-Ray Moon
| Title |
X-Ray Moon |
| Explanation |
This x-ray image [ http://heasarc.gsfc.nasa.gov/docs/rosat/gallery/ misc_moon2.html ] of the Moon [ http://antwrp.gsfc.nasa.gov/apod/ap960919.html ] was made by the orbiting ROSAT [ http://heasarc.gsfc.nasa.gov/docs/rosat/rhp_geninfo.html ] (Röntgensatellit [ http://heasarc.gsfc.nasa.gov/docs/rosat/gallery/ wilhelm.html ]) Observatory in 1990. In this digital picture, pixel brightness corresponds to x-ray intensity. Consider the image in three parts: the bright hemisphere of the x-ray moon, the darker half of the moon, and the x-ray sky [ http://antwrp.gsfc.nasa.gov/apod/ap000819.html ] background. The bright lunar hemisphere shines in x-rays [ http://imagine.gsfc.nasa.gov/docs/science/know_l1/ history1_xray.html ] because it reflects x-rays emitted by the sun ... just as it shines at night [ http://antwrp.gsfc.nasa.gov/apod/ap000113.html ] by reflecting visible sunlight. The background [ http://heasarc.gsfc.nasa.gov/docs/objects/ background/background.html ] sky has an x-ray glow in part due to the myriad of distant, powerful active galaxies, unresolved in the ROSAT picture but recently detected in Chandra Observatory x-ray images [ http://antwrp.gsfc.nasa.gov/apod/ap000114.html ]. But why isn't the dark half of the moon completely dark? It's true that the dark lunar face is in shadow [ http://antwrp.gsfc.nasa.gov/apod/ap980312.html ] and so is not reflecting solar x-rays [ http://antwrp.gsfc.nasa.gov/apod/ap981221.html ]. Still, the few x-ray photons which seem to come from the moon's dark half are currently thought to be caused by energetic particles in the solar wind [ http://www-spof.gsfc.nasa.gov/Education/wsolwind.html ] bombarding the lunar surface. |
|
A Perseid Aurora
| Title |
A Perseid Aurora |
| Explanation |
Just after the Moon set [ http://aa.usno.navy.mil/AA/data/docs/RS_OneYear.html ] but before the Sun rose [ http://antwrp.gsfc.nasa.gov/apod/ap991110.html ] in the early morning hours of August 12, meteors [ http://www.amsmeteors.org/showers.html ] pelted the Earth from the direction of the constellation Perseus [ http://www.seds.org/Maps/Stars_en/Fig/perseus.html ], while ions [ http://ParticleAdventure.org/ ] pelted the Earth from the Sun [ http://www.seds.org/nineplanets/nineplanets/sol.html ]. The meteors [ http://www.seds.org/nineplanets/nineplanets/meteorites.html ] were expected as sub-sand grains long left behind by Comet Swift-Tuttle [ http://antwrp.gsfc.nasa.gov/apod/ap960219.html ] annually create the Perseids Meteor Shower [ http://www.science.nasa.gov/newhome/headlines/ast09aug99_1.htm ]. The aurorae [ http://www.geo.mtu.edu/weather/aurora/ ] were unexpected, however, as electrons [ http://www.aip.org/history/electron/ ], protons [ http://hyperphysics.phy-astr.gsu.edu/hbase/particles/proton.html ], and heavier ions [ http://www-spof.gsfc.nasa.gov/Education/Ielect.html ] raced out from a large Coronal Mass Ejection [ http://science.nasa.gov/ssl/pad/solar/cmes.htm ] that had occurred [ http://antwrp.gsfc.nasa.gov/apod/ap000817.html ] just days before on the Sun. In the foreground is Hahn's Peak, an extinct volcano in Colorado [ http://www.state.co.us/ ], USA [ http://www.odci.gov/cia/publications/factbook/us.html ]. |
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The Car, the Hole, and the P
…
| Title |
The Car, the Hole, and the Peekskill Meteorite |
| Explanation |
The Peekskill meteor [ http://uregina.ca/~astro/mb_5.html ] of 1992 was captured on 16 independent video [ http://aquarid.physics.uwo.ca/~pbrown/Videos/peekskill.htm ]s and then struck a car. Documented [ http://nyrockman.com/peekskill.htm ] as brighter than the full Moon [ http://antwrp.gsfc.nasa.gov/apod/ap020316.html ], the spectacular fireball [ http://starchild.gsfc.nasa.gov/docs/StarChild/shadow/solar_system_level2/peekskill.html ] crossed parts of several US [ https://cia.gov/cia//publications/factbook/geos/us.html ] states during its 40 seconds of glory before landing in Peekskill [ http://www.hudsonriver.com/rivertowns/peekskill.htm ], New York [ http://en.wikipedia.org/wiki/New_York ]. The resulting meteorite [ http://www.nineplanets.org/meteorites.html ], pictured here, is composed of dense rock and has the size and mass of an extremely heavy bowling ball [ http://www2.ncsu.edu/ncsu/pams/science_house/learn/floatingballs.html ]. If you are lucky [ http://video.google.com/videoplay?docid=-4683502345579146769 ] enough to find a meteorite [ http://en.wikipedia.org/wiki/Meteorite ] just after impact [ http://antwrp.gsfc.nasa.gov/apod/ap990711.html ], do not pick it up -- parts of it are likely to be either very hot or very cold. In this weekend [ http://www.arm.ac.uk/leonid/2006/info2006.html ]'s Leonid meteor shower [ http://comets.amsmeteors.org/meteors/showers/leonidsez.html ], few meteors, if any, are expected to hit [ http://antwrp.gsfc.nasa.gov/apod/ap020623.html ] the ground. |
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X-Ray Moon and X-Ray Star
| Title |
X-Ray Moon and X-Ray Star |
| Explanation |
An x-ray star [ http://imagine.gsfc.nasa.gov/docs/science/know_l2/binaries.html ] winks out behind the Moon in these [ http://heasarc.gsfc.nasa.gov/docs/rosat/gallery/ misc_gx5-1_moon_occult.html ] before (left) and after views of a lunar occultation [ http://www.skypub.com/sights/occultations/occultations.shtml ] of the galactic x-ray source designated GX5-1 [ http://antwrp.gsfc.nasa.gov/apod/ap000909.html http://adsabs.harvard.edu/cgi-bin/ nph-bib_query?bibcode=1997PASJ...49..589K&db_key=AST&high=3899d8d98228744 ]. The false color images were made using data from the ROSAT [ http://heasarc.gsfc.nasa.gov/docs/rosat/rosat3.html ] (ROentgen SATellite), orbiting observatory. They show high energy x-rays in yellow (mostly from GX5-1), and lower energy x-rays in red (the Moon reflecting x-rays [ http://antwrp.gsfc.nasa.gov/apod/ap000902.html ] from the Sun). GX5-1 is a binary system [ http://heasarc.gsfc.nasa.gov/docs/binary.html ] consisting of a neutron star [ http://antwrp.gsfc.nasa.gov/apod/lib/glossary.html#ns ] and a companion star in mutual orbit about the system's center of mass. The gas in the companion star's outer envelope falls toward the neutron star and accumulates in a disk [ http://antwrp.gsfc.nasa.gov/apod/ap991219.html ] around it. This disk material swirls deeper in to the neutron star's gravitational well [ http://antwrp.gsfc.nasa.gov/htmltest/rjn_bht.html ], and is finally dumped onto its surface - in the process creating tremendous temperatures and generating the high energy x-rays. |
|
Halo and Hexagons
| Title |
Halo and Hexagons |
| Explanation |
As a bright November Moon lit up the night sky last week, Gil Esquerdo spotted this lovely Moon halo overhead [ http://www.atoptics.co.uk/ ] at the Whipple Observatory on Mt. Hopkins, Arizona. In the foreground, the structure and individual component mirrors of Whipple's 10 meter gamma-ray telescope [ http://veritas.sao.arizona.edu/old/ VERITAS_whipple_photos.html ] actually block direct light from the lunar disk, emphasizing the halo in this dramatic view. The halo was caused by ice crystals in the thin high clouds above the observatory - crystals that are hexagonal in shape [ http://hyperphysics.phy-astr.gsu.edu/hbase/atmos/ moonhalo.html ] and produce the characteristic ring of light with a 22 degree radius. In fact, the ice crystal shapes are much like the flat, hexagonal mirrors of the specialized [ http://antwrp.gsfc.nasa.gov/apod/ap041015.html ] telescope in the picture. Used together the mirrors can collect brief flashes of optical light caused by high-energy gamma-rays impacting [ http://imagine.gsfc.nasa.gov/docs/science/how_l2/ cerenkov.html ] Earth's atmosphere. |
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M82's Middle Mass Black Hole
| Title |
M82's Middle Mass Black Hole |
| Explanation |
Black holes [ http://www.ncsa.uiuc.edu/Cyberia/NumRel/BlackHoles.html ] are probably the most bizarre [ http://antwrp.gsfc.nasa.gov/htmltest/rjn_bht.html ] creatures in the modern astronomical zoo. And after years of pondering black holes [ http://chandra.harvard.edu/xray_sources/blackholes.html ] as either stellar mass objects seen in binary star systems [ http://imagine.gsfc.nasa.gov/docs/features/movies/ binaries.html ] or enormous supermassive black holes at the centers of galaxies [ http://oposite.stsci.edu/pubinfo/PR/2000/22/ index.html ], astronomers now have strong evidence for another exotic species -- middle mass black holes [ http://chandra.harvard.edu/press/00_releases/ press_091200.html ]. The leading candidate for the ultradense middle ground is indicated in this false-color detail of a sharp x-ray picture from the space-based Chandra Observatory. A close-up of x-ray sources near the center of starburst galaxy M82 [ http://antwrp.gsfc.nasa.gov/apod/ap000421.html ], the cropped Chandra image [ http://chandra.harvard.edu/photo/cycle1/0094/index.html ] spans about 4,000 light-years. M82 itself is around 11 million light-years distant. The arrowed source has recently been convincingly demonstrated to exhibit x-ray characteristics [ http://chandra.harvard.edu/xray_sources/ bh_midmass3.html ] of an object whose gravitational field holds more than 500 times the mass of the sun within a volume the size of the moon! Astronomers also note [ http://chandra.harvard.edu/photo/cycle1/m82bh/index.html ] that unlike the supermassive variety which are thought to lie at the centers of galaxies, this middle mass black hole is about 600 light-years from the center of M82. Theories for the formation of a middle mass black hole include the collapse of a "hyperstar" formed by the coalescence [ http://www.physics.uiuc.edu/Research/cta/movies/se/ max_boltz.html ] of many normal stars, or the direct merger of [ http://www.physics.uiuc.edu/Research/cta/movies/se/ collide.html ] stellar mass black holes. |
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Sputnik: Traveling Companion
| Title |
Sputnik: Traveling Companion |
| Explanation |
Sputnik means [ http://www.hq.nasa.gov/office/pao/History/sputnik/index.html ]"traveling companion". Despite the innocuous sounding name, the launch [ http://www.nytimes.com/partners/aol/special/sputnik/ launch.1.jpg.html ] of the Earth's first "artificial moon", Sputnik 1 [ http://www.nytimes.com/partners/aol/special/sputnik/ ], by the Soviet Union on October 4, 1957 shocked the free world, setting in motion events which resulted in the creation of NASA [ http://antwrp.gsfc.nasa.gov/apod/ap981001.html ] and the race to the Moon [ http://antwrp.gsfc.nasa.gov/apod/ap970202.html ]. Sputnik 1 [ http://whyfiles.org/047sputnik/main1.html ] was a 184 pound, 22 inch diameter sphere with four whip antennas connected to battery powered transmitters. The transmitters broadcast a continuous "beeping" signal to an astounded [ http://www.sciam.com/explorations/100697sputnik/ hall1.html ] earthbound audience for 23 days. A short month later, on November 3, the Soviet Union followed this success by launching a dog [ http://ham.spa.umn.edu/kris/animals.html ] into orbit aboard Sputnik 2 [ http://asca.gsfc.nasa.gov/docs/StarChild/space_level2/laika.html ]. |
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Apollo 17 Panorama: Astronau
…
| Title |
Apollo 17 Panorama: Astronaut Running |
| Explanation |
What would it be like to explore the surface of another world? In 1972 during the Apollo 17 [ http://www.hq.nasa.gov/alsj/a17/a17j.html ] mission, astronaut Harrison Schmitt [ http://www.jsc.nasa.gov/Bios/htmlbios/schmitt-hh.html ] found out first hand. In this case, the world was Earth [ http://antwrp.gsfc.nasa.gov/apod/ap001127.html ]'s own Moon [ http://www.nineplanets.org/luna.html ]. In this recently compiled panorama of lunar photographs originally taken by astronaut Eugene Cernan [ http://www.jsc.nasa.gov/Bios/htmlbios/cernan-ea.html ], the magnificent desolation [ http://antwrp.gsfc.nasa.gov/apod/ap001209.html ] of the barren Moon [ http://antwrp.gsfc.nasa.gov/apod/ap981031.html ] is apparent. Visible above and by scrolling right are lunar rocks [ http://csep10.phys.utk.edu/astr161/lect/moon/moon_surface.html ] in the foreground, lunar mountains [ http://antwrp.gsfc.nasa.gov/apod/ap980705.html ] in the background, some small craters, a lunar rover [ http://starchild.gsfc.nasa.gov/docs/StarChild/space_level2/apollo15_rover.html ], and astronaut Schmidt on his way back to the rover. A few days after this image [ http://www.hq.nasa.gov/alsj/a17/a17.sta1.html#1222614 ] was taken, humanity left the Moon [ http://en.wikipedia.org/wiki/Moon ] and has yet to return. |
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NGC 6960: The Witch's Broom
…
| Title |
NGC 6960: The Witch's Broom Nebula |
| Explanation |
Ten thousand years ago, before the dawn of recorded human history [ http://news.bbc.co.uk/hi/english/sci/tech/newsid_334000/334517.stm ], a new light must suddenly have appeared in the night sky and faded after a few weeks. Today we know this light was an exploding star [ http://imagine.gsfc.nasa.gov/docs/science/know_l1/supernovae.html ] and record the colorful expanding cloud as the Veil Nebula [ http://antwrp.gsfc.nasa.gov/apod/ap010928.html ]. Pictured above [ http://www.noao.edu/image_gallery/html/im0852.html ] is the west end of the Veil Nebula [ http://antwrp.gsfc.nasa.gov/apod/ap030204.html ] known technically as NGC [ http://en.wikipedia.org/wiki/New_General_Catalog ] 6960 but less formally as the Witch [ http://antwrp.gsfc.nasa.gov/apod/ap061211.html ]'s Broom [ http://www.broomshop.com/history/ ] Nebula. The rampaging gas gains its colors by impacting and exciting existing [ http://www.seds.org/billa/twn/cygnusx.html ] nearby gas. The supernova remnant [ http://antwrp.gsfc.nasa.gov/apod/supernova_remnants.html ] lies about 1400 light-years [ http://starchild.gsfc.nasa.gov/docs/StarChild/questions/question19.html ] away towards the constellation of Cygnus [ http://www.multimania.com/cdadfs/constellation/cygne/cygnus.htm ]. This Witch's Broom actually spans over three times the angular size [ http://imagine.gsfc.nasa.gov/YBA/HTCas-size/more-ang_size.html ] of the full Moon [ http://antwrp.gsfc.nasa.gov/apod/ap030810.html ]. The bright star 52 Cygnus [ http://www.seds.org/Maps/Stars_en/Fig/cygnus.html ] is visible with the unaided eye from a dark location but unrelated to the ancient supernova [ http://en.wikipedia.org/wiki/Supernova ]. |
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M8: In the Center of the Lag
…
| Title |
M8: In the Center of the Lagoon Nebula |
| Explanation |
In the center of the Lagoon Nebula [ http://www.seds.org/messier/m/m008.html ] one finds glowing gas [ http://antwrp.gsfc.nasa.gov/apod/emission_nebulae.html ], star clusters, and dense knots of gas and dust [ http://antwrp.gsfc.nasa.gov/apod/ap961229.html ] just now forming stars. The young open cluster [ http://antwrp.gsfc.nasa.gov/apod/open_clusters.html ] of stars, designated NGC 6523, can be seen in the center of the above image [ http://www.janis.or.jp/users/kitahara/e-m8-95.jpg.html ]. These stars emit energetic light [ http://snoopy.gsfc.nasa.gov/~orfeus2/ultraviolet.html ] that ionizes [ http://csep10.phys.utk.edu/astr162/lect/light/ionization.html ] the surrounding hydrogen [ http://pearl1.lanl.gov/periodic/elements/1.html ] gas. As this gas reacquires electrons [ http://www.aip.org/history/electron/ ], it emits red light [ http://csep10.phys.utk.edu/astr162/lect/light/absorption.html ]. The Lagoon Nebula [ http://www.seds.org/billa/twn/n6523x.html ] lies about 5000 light-years [ http://starchild.gsfc.nasa.gov/docs/StarChild/questions/question19.html ] away and spans about 100 light-years across. The nebula [ http://antwrp.gsfc.nasa.gov/apod/ap980707.html ] occupies an area on the sky larger than a full moon [ http://antwrp.gsfc.nasa.gov/apod/ap991108.html ], and can be seen even without binoculars from a dark location towards the constellation [ http://www.allthesky.com/constellations/const.html ] of Sagittarius [ http://www.astronomical.org/constellations/sgr.html ]. |
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Eclipsed Moon and Stars
| Title |
Eclipsed Moon and Stars |
| Explanation |
This dramatic image [ http://panther-observatory.com/gallery/moon/doc/ Mofi_03032007_cass.htm ] features a dark red Moon during a total lunar eclipse -- celestial shadow play [ http://antwrp.gsfc.nasa.gov/apod/ap060909.html ] enjoyed by many denizens of planet Earth [ http://spaceweather.com/eclipses/gallery_03mar07.htm ] last Saturday. Recorded near Wildon, Austria, the picture is a composite of two exposures, a relatively short exposure to feature the lunar surface and a longer exposure to capture background stars in the constellation Leo [ http://www.seds.org/Maps/Stars_en/Fig/leo.html ]. Completely immersed in Earth's cone-shaped shadow during the total eclipse [ http://www.inconstantmoon.com/cyc_ecl1.htm ] phase, the lunar surface is still illuminated by sunlight, reddened and [ http://antwrp.gsfc.nasa.gov/apod/ap031121.html ] refracted into the dark shadow region by a dusty atmosphere. As a result, familiar [ http://antwrp.gsfc.nasa.gov/apod/ap031212.html ] details of the Moon's nearside are easy to pick out, including the smooth lunar mare and the large ray crater Tycho [ http://antwrp.gsfc.nasa.gov/apod/ap050305.html ]. In this telescopic view, the background stars are faint and most would be invisible to the naked eye. |
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Vela Supernova Remnant in Vi
…
| Title |
Vela Supernova Remnant in Visible Light |
| Explanation |
The explosion is over but the consequences continue. About eleven thousand years ago a star in the constellation of Vela [ http://www.hawastsoc.org/deepsky/vel/index.html ] could be seen to explode [ http://www.youtube.com/watch?v=gL1xUWgBlFw ], creating a strange point of light briefly visible to humans living near the beginning of recorded history [ http://en.wikipedia.org/wiki/Cave_painting ]. The outer layers of the star crashed into the interstellar medium [ http://antwrp.gsfc.nasa.gov/apod/ap020210.html ], driving a shock wave [ http://antwrp.gsfc.nasa.gov/apod/ap020313.html ] that is still visible today. A roughly spherical, expanding shock wave is visible in X-rays [ http://antwrp.gsfc.nasa.gov/apod/ap960612.html ]. The above image [ http://www.skyfactory.org/vela/vela.htm ] captures much of that filamentary and gigantic shock in visible light [ http://imagers.gsfc.nasa.gov/ems/visible.html ], spanning almost 100 light years [ http://chandra.harvard.edu/photo/cosmic_distance.html ] and appearing twenty times the diameter of the full moon [ http://antwrp.gsfc.nasa.gov/apod/ap051113.html ]. As gas flies away from the detonated star, it decays [ http://imagine.gsfc.nasa.gov/docs/features/exhibit/cgro_snr.html ] and reacts with the interstellar medium, producing light in many different colors and energy bands. Remaining at the center of the Vela Supernova Remnant [ http://en.wikipedia.org/wiki/Vela_Supernova_Remnant ] is a pulsar [ http://imagine.gsfc.nasa.gov/docs/science/know_l1/pulsars.html ], a star as dense as nuclear matter that completely rotates more than ten times in a single second. |
|
Solstice And Season's Eclips
…
| Title |
Solstice And Season's Eclipse |
| Explanation |
Today the Sun reaches its southernmost point [ http://www-spof.gsfc.nasa.gov/stargaze/Sseason.htm ] in planet Earth's sky at 13:37 UT [ http://aa.usno.navy.mil/AA/faq/docs/UT.html ]. This celestial event is known as a solstice, marking the beginning of Summer [ http://antwrp.gsfc.nasa.gov/apod/ap951222.html ] in the Southern Hemisphere and Winter in the North. But this year, the solstice will be followed, on December 25th, by another geocentric celestial event [ http://aa.usno.navy.mil/AA/data/docs/EarthSeasons.html ] -- the last eclipse of the millennium [ http://www.usno.navy.mil/millennium/ ]! The Christmas day eclipse [ http://sunearth.gsfc.nasa.gov/eclipse/extra/ PSE2000Dec25.html ] will only be a partial one as the silhouetted disk of the Moon obscures the Sun's edge. Visible [ http://sunearth.gsfc.nasa.gov/eclipse/SEplot/ SE2000Dec25P.gif ] from much of Canada [ http://sunearth.gsfc.nasa.gov/eclipse/extra/ PSE2000Dec25city2/PSE2000Dec25city2.html ], The United States [ http://sunearth.gsfc.nasa.gov/eclipse/extra/ PSE2000Dec25city1/PSE2000Dec25city1.html ] and Mexico [ http://sunearth.gsfc.nasa.gov/eclipse/extra/ PSE2000Dec25city3/PSE2000Dec25city3.html ], the appearance of the partially eclipsed Sun might remind you of the last holiday cookie [ http://www.cs.cmu.edu/~mjw/recipes/cookies/cookie.html ] you took a bite from. Still, the exact timing and degree of the eclipse will depend very much on your location. This image, from an annular eclipse [ http://www.astrosurf.com/alphaweb/10mai94/ ] in 1994, shows the lunar disk covering around 55% of the Sun's diameter. It is representative of what could be seen from Washington D. C. during the December 25 eclipse maximum which, for that location, occurs at 12:41 PM ET. As always, if you view the eclipse be extremely careful [ http://www.mreclipse.com/Totality/ TotalityCh11.html#Intro ] to protect your eyes. |
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Nashville Four Planet Skylin
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| Title |
Nashville Four Planet Skyline |
| Explanation |
So far this February, evening skies [ http://antwrp.gsfc.nasa.gov/apod/ap000504.html ] have been blessed with a glorious Moon and three bright planets, Venus [ http://www.library.utoronto.ca/utel/rp/poems/ longfe10.html ], Jupiter, and Saturn. But just last week, on January 30th, an extreme wide-angle lens allowed astrophotographer Larry Koehn to capture this twilight view of Moon and four planets above [ http://www.seds.org/nineplanets/nineplanets/ see.html ] Nashville, Tennessee, USA. These major solar system [ http://space.jpl.nasa.gov/ ] bodies lie along the ecliptic plane [ http://antwrp.gsfc.nasa.gov/apod/ap001014.html ] and so follow a diagonal line through the picture. Starting near the upper left corner is bright Jupiter [ http://starchild.gsfc.nasa.gov/docs/StarChild/ solar_system_level2/jupiter.html ], which takes on a slightly triangular shape due to the lens distortion. Just below and right of Jupiter is Saturn [ http://www.jpl.nasa.gov/cassini/english/kids/ saturn_in_sky.html ]. Continuing along the diagonal toward the lower right is an overexposed, six day old Moon [ http://www.inconstantmoon.com/ ] and brilliant Venus seemingly embedded in clouds. The fourth planet pictured is Mercury. Notoriously hard to see from planet Earth because it never wanders far from the Sun, Mercury is [ http://antwrp.gsfc.nasa.gov/apod/ap991111.html ] visible just above the lower right corner. The line from Jupiter to Mercury spans about 92 degrees across the Nashville sky. |
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Distant Open Cluster M103
| Title |
Distant Open Cluster M103 |
| Explanation |
Bright blue stars highlight the open cluster known as M103 [ http://www.seds.org/messier/m/m103.html ]. The gas clouds [ http://antwrp.gsfc.nasa.gov/apod/ap000924.html ] from which these stars condensed has long dispersed. Of the stars that were formed, the brightest, bluest, and most massive have already used up their nuclear fuel [ http://observe.ivv.nasa.gov/nasa/space/stellardeath/stellardeath_intro.html ] and self-destructed in supernova explosions [ http://heasarc.gsfc.nasa.gov/docs/snr.html ]. A 20 million-year age for M103 was estimated by finding the brightest main-sequence stars [ http://zebu.uoregon.edu/~js/ast122/lectures/lec15.html ] that still survive and theoretically computing their lifetimes. In fact, a formerly blue star has recently evolved off the main sequence [ http://antwrp.gsfc.nasa.gov/htmltest/gifcity/msblues.html ] and is visible above [ http://www.noao.edu/image_gallery/html/im0635.html ] as the red giant star [ http://zebu.uoregon.edu/~js/ast122/lectures/lec17.html ] near the cluster center. In general, yellow stars like our Sun [ http://antwrp.gsfc.nasa.gov/apod/sun.html ] are usually less bright and hence less prominent in open clusters [ http://antwrp.gsfc.nasa.gov/apod/open_clusters.html ] than their massive blue cousins. Light takes about 14 years [ http://chandra.harvard.edu/photo/cosmic_distance.html ] to cross M103 [ http://www.e-z.net/~haworth/messier/m103.html ]. Although visible with binoculars toward the constellation [ http://www.seds.org/Maps/Const/constS.html ] of Cassiopeia [ http://www.astronomical.org/constellations/cas.html ], M103 [ http://adsabs.harvard.edu/cgi-bin/nph-bib_query?bibcode=1999A%26A...349..448S ]'s great distance of 8000 light years makes it appear four times smaller than a full moon [ http://antwrp.gsfc.nasa.gov/apod/ap000113.html ]. |
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Shuttle Plume Shadow Points
…
| Title |
Shuttle Plume Shadow Points to Moon |
| Explanation |
Why would the shadow of a space shuttle [ http://www.dfrc.nasa.gov/EAO/FactSheets/ShuttlesFACTS.html ] launch plume point toward the Moon? Two weeks ago during the launch of Atlantis [ http://science.ksc.nasa.gov/shuttle/resources/orbiters/atlantis.html ], the Sun [ http://antwrp.gsfc.nasa.gov/apod/sun.html ], Earth, Moon [ http://www.nineplanets.org/luna.html ], and rocket were all properly aligned for this photogenic coincidence. First, for the space shuttle [ http://www.shuttlepresskit.com/STS-98/index.htm ]'s plume to cast a long shadow, the time of day must be either near sunrise [ http://antwrp.gsfc.nasa.gov/apod/ap990817.html ] or sunset [ http://antwrp.gsfc.nasa.gov/apod/ap980526.html ]. Next, just at sunset, the shadow [ http://antwrp.gsfc.nasa.gov/apod/ap001225.html ] is the longest and extends all the way to the horizon [ http://antwrp.gsfc.nasa.gov/apod/ap990619.html ]. Finally, during a Full Moon [ http://antwrp.gsfc.nasa.gov/apod/ap000113.html ], the Sun [ http://antwrp.gsfc.nasa.gov/apod/ap010129.html ] and Moon [ http://antwrp.gsfc.nasa.gov/apod/moon.html ] are on opposite sides of the sky. Just after sunset [ http://antwrp.gsfc.nasa.gov/apod/ap991110.html ], for example, the Sun is slightly below the horizon [ http://www.dictionary.com/cgi-bin/dict.pl?term=horizon ], and, in the other direction, the Moon is slightly above the horizon [ http://antwrp.gsfc.nasa.gov/apod/ap000320.html ]. Therefore, as Atlantis [ http://antwrp.gsfc.nasa.gov/apod/ap950812.html ] blasted off, just after sunset [ http://antwrp.gsfc.nasa.gov/apod/ap990726.html ], its shadow projected away from the Sun toward the opposite horizon, where the Full Moon [ http://antwrp.gsfc.nasa.gov/apod/ap010104.html ] just happened to be. |
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Apollo 12 Visits Surveyor 3
| Title |
Apollo 12 Visits Surveyor 3 |
| Explanation |
Apollo 12 [ http://nssdc.gsfc.nasa.gov/planetary/lunar/apollo12info.html ] was the second mission to land humans [ http://www.badastronomy.com/bad/tv/foxapollo.html ] on the Moon [ http://antwrp.gsfc.nasa.gov/apod/moon.html ]. The landing site was picked to be near the location of Surveyor [ http://nssdc.gsfc.nasa.gov/planetary/lunar/surveyor.html ] 3, a robot spacecraft that had landed on the Moon [ http://www.nineplanets.org/luna.html ] three years earlier. In the above photograph [ http://www.hq.nasa.gov/alsj/a12/ images12.html#HiRes ], taken by lunar module pilot Alan Bean [ http://www.nasm.edu/apollo/AS12/a12crew.htm ], mission commander Pete Conrad [ http://antwrp.gsfc.nasa.gov/apod/ap990715.html ] retrieves parts from the Surveyor. The lunar module [ http://www.moonlander.com/lmdata/ ] is visible [ http://antwrp.gsfc.nasa.gov/apod/ap951007.html ] in the distance. Apollo 12 [ http://www.nasm.edu/apollo/AS12/a12.htm ] brought back many photographs and moon rocks. Among the milestones achieved by Apollo 12 was the deployment [ http://antwrp.gsfc.nasa.gov/apod/ap951210.html ] of the Apollo Lunar Surface Experiments Package [ http://antwrp.gsfc.nasa.gov/apod/ap010303.html http://www-sn.jsc.nasa.gov/PlanetaryMissions/EXLibrary/ docs/ApolloCat/Part1/ALSEP.htm ], which carried out many experiments including one that measured the solar wind [ http://antwrp.gsfc.nasa.gov/apod/ap000318.html ]. |
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Great Mountain Moonrise
| Title |
Great Mountain Moonrise |
| Explanation |
On May 31st, a gorgeous Full Moon rose over Uludag Mountain [ http://en.wikipedia.org/wiki/Uluda%C4%9F ] in Bursa Province, Turkey. This alluring telephoto view of the twilight [ http://antwrp.gsfc.nasa.gov/apod/ap050611.html ] scene is a composite of images taken roughly every two minutes beginning shortly after Sunset, following the rising Moon as it moves up and to the right. Of course, as the Moon rises it gets brighter and changes color, becoming less reddened [ http://webexhibits.org/causesofcolor/14B.html ] as the sight-line through the dense atmosphere [ http://www.atoptics.co.uk/ ] is steadily reduced. Each of the final two exposures also captured a rising planet Jupiter. Like the Full Moon [ http://starchild.gsfc.nasa.gov/docs/StarChild/questions/ question3.html ], the bright, wandering planet is nearly opposite [ http://www.heavens-above.com/gloss.asp?term=opposition ] the Sun in Earth's sky and was caught on the lefthand side of the picture in two places, just above a small peak in the mountain side. Intriguingly, some considered this Full Moon a Blue Moon [ http://science.nasa.gov/headlines/y2007/ 30may_bluemoon.htm ]. |
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