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Moon and Sun of Goddard Space Flight Center (GSFC)
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Iapetus Thermal Radiation Im
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| Description |
Iapetus Thermal Radiation Image |
| Full Description |
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 Temperature Variatio
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| Description |
Iapetus Temperature Variation Map |
| Full Description |
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 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 Temperature Maps
| Description |
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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Hubble Follows Rapid Changes
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| Title |
Hubble Follows Rapid Changes in Jupiter's Aurora |
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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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STEREO's Routes to Solar Orb
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| Title |
STEREO's Routes to Solar Orbits |
| Abstract |
The two STEREO spacecraft, A (red path) and B (yellow path), are launched from the Earth into a highly eccentric orbit with an apogee that reaches the orbit of the Moon. Once in this orbit, the trajectories are adjusted so they can receive gravity-assists from the Moon. The gravity assist will send them both into heliocentric orbits, one spacecraft ahead of the Earth and the other behind the Earth. This trajectory was generated using a spacecraft ephemeris generated shortly after launch. |
| Completed |
2007-02-05 |
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STEREO's Routes to Solar Orb
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| Title |
STEREO's Routes to Solar Orbits |
| Abstract |
The two STEREO spacecraft, A (red path) and B (yellow path), are launched from the Earth into a highly eccentric orbit with an apogee that reaches the orbit of the Moon. Once in this orbit, the trajectories are adjusted so they can receive gravity-assists from the Moon. The gravity assist will send them both into heliocentric orbits, one spacecraft ahead of the Earth and the other behind the Earth. This trajectory was generated using a spacecraft ephemeris generated shortly after launch. |
| Completed |
2007-02-05 |
|
STEREO's Routes to Solar Orb
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| Title |
STEREO's Routes to Solar Orbits |
| Abstract |
The two STEREO spacecraft, A (red path) and B (yellow path), are launched from the Earth into a highly eccentric orbit with an apogee that reaches the orbit of the Moon. Once in this orbit, the trajectories are adjusted so they can receive gravity-assists from the Moon. The gravity assist will send them both into heliocentric orbits, one spacecraft ahead of the Earth and the other behind the Earth. This trajectory was generated using a spacecraft ephemeris generated shortly after launch. |
| Completed |
2007-02-05 |
|
STEREO's Routes to Solar Orb
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| Title |
STEREO's Routes to Solar Orbits |
| Abstract |
The two STEREO spacecraft, A (red path) and B (yellow path), are launched from the Earth into a highly eccentric orbit with an apogee that reaches the orbit of the Moon. Once in this orbit, the trajectories are adjusted so they can receive gravity-assists from the Moon. The gravity assist will send them both into heliocentric orbits, one spacecraft ahead of the Earth and the other behind the Earth. This trajectory was generated using a spacecraft ephemeris generated shortly after launch. |
| Completed |
2007-02-05 |
|
STEREO's Routes to Solar Orb
…
| Title |
STEREO's Routes to Solar Orbits |
| Abstract |
The two STEREO spacecraft, A (red path) and B (yellow path), are launched from the Earth into a highly eccentric orbit with an apogee that reaches the orbit of the Moon. Once in this orbit, the trajectories are adjusted so they can receive gravity-assists from the Moon. The gravity assist will send them both into heliocentric orbits, one spacecraft ahead of the Earth and the other behind the Earth. This trajectory was generated using a spacecraft ephemeris generated shortly after launch. |
| Completed |
2007-02-05 |
|
STEREO's Routes to Solar Orb
…
| Title |
STEREO's Routes to Solar Orbits |
| Abstract |
The two STEREO spacecraft, A (red path) and B (yellow path), are launched from the Earth into a highly eccentric orbit with an apogee that reaches the orbit of the Moon. Once in this orbit, the trajectories are adjusted so they can receive gravity-assists from the Moon. The gravity assist will send them both into heliocentric orbits, one spacecraft ahead of the Earth and the other behind the Earth. This trajectory was generated using a spacecraft ephemeris generated shortly after launch. |
| Completed |
2007-02-05 |
|
STEREO's Routes to Solar Orb
…
| Title |
STEREO's Routes to Solar Orbits |
| Abstract |
The two STEREO spacecraft, A (red path) and B (yellow path), are launched from the Earth into a highly eccentric orbit with an apogee that reaches the orbit of the Moon. Once in this orbit, the trajectories are adjusted so they can receive gravity-assists from the Moon. The gravity assist will send them both into heliocentric orbits, one spacecraft ahead of the Earth and the other behind the Earth. This trajectory was generated using a spacecraft ephemeris generated shortly after launch. |
| Completed |
2007-02-05 |
|
STEREO's Routes to Solar Orb
…
| Title |
STEREO's Routes to Solar Orbits |
| Abstract |
The two STEREO spacecraft, A (red path) and B (yellow path), are launched from the Earth into a highly eccentric orbit with an apogee that reaches the orbit of the Moon. Once in this orbit, the trajectories are adjusted so they can receive gravity-assists from the Moon. The gravity assist will send them both into heliocentric orbits, one spacecraft ahead of the Earth and the other behind the Earth. This trajectory was generated using a spacecraft ephemeris generated shortly after launch. |
| Completed |
2007-02-05 |
|
STEREO's Routes to Solar Orb
…
| Title |
STEREO's Routes to Solar Orbits |
| Abstract |
The two STEREO spacecraft, A (red path) and B (yellow path), are launched from the Earth into a highly eccentric orbit with an apogee that reaches the orbit of the Moon. Once in this orbit, the trajectories are adjusted so they can receive gravity-assists from the Moon. The gravity assist will send them both into heliocentric orbits, one spacecraft ahead of the Earth and the other behind the Earth. This trajectory was generated using a spacecraft ephemeris generated shortly after launch. |
| Completed |
2007-02-05 |
|
STEREO's Routes to Solar Orb
…
| Title |
STEREO's Routes to Solar Orbits |
| Abstract |
The two STEREO spacecraft, A (red path) and B (yellow path), are launched from the Earth into a highly eccentric orbit with an apogee that reaches the orbit of the Moon. Once in this orbit, the trajectories are adjusted so they can receive gravity-assists from the Moon. The gravity assist will send them both into heliocentric orbits, one spacecraft ahead of the Earth and the other behind the Earth. This trajectory was generated using a spacecraft ephemeris generated shortly after launch. |
| Completed |
2007-02-05 |
|
STEREO's Routes to Solar Orb
…
| Title |
STEREO's Routes to Solar Orbits |
| Abstract |
The two STEREO spacecraft, A (red path) and B (yellow path), are launched from the Earth into a highly eccentric orbit with an apogee that reaches the orbit of the Moon. Once in this orbit, the trajectories are adjusted so they can receive gravity-assists from the Moon. The gravity assist will send them both into heliocentric orbits, one spacecraft ahead of the Earth and the other behind the Earth. This trajectory was generated using a spacecraft ephemeris generated shortly after launch. |
| Completed |
2007-02-05 |
|
STEREO's Routes to Solar Orb
…
| Title |
STEREO's Routes to Solar Orbits |
| Abstract |
The two STEREO spacecraft, A (red path) and B (yellow path), are launched from the Earth into a highly eccentric orbit with an apogee that reaches the orbit of the Moon. Once in this orbit, the trajectories are adjusted so they can receive gravity-assists from the Moon. The gravity assist will send them both into heliocentric orbits, one spacecraft ahead of the Earth and the other behind the Earth. This trajectory was generated using a spacecraft ephemeris generated shortly after launch. |
| Completed |
2007-02-05 |
|
STEREO's Routes to Solar Orb
…
| Title |
STEREO's Routes to Solar Orbits |
| Abstract |
The two STEREO spacecraft, A (red path) and B (yellow path), are launched from the Earth into a highly eccentric orbit with an apogee that reaches the orbit of the Moon. Once in this orbit, the trajectories are adjusted so they can receive gravity-assists from the Moon. The gravity assist will send them both into heliocentric orbits, one spacecraft ahead of the Earth and the other behind the Earth. This trajectory was generated using a spacecraft ephemeris generated shortly after launch. |
| Completed |
2007-02-05 |
|
STEREO's Routes to Solar Orb
…
| Title |
STEREO's Routes to Solar Orbits |
| Abstract |
The two STEREO spacecraft, A (red path) and B (yellow path), are launched from the Earth into a highly eccentric orbit with an apogee that reaches the orbit of the Moon. Once in this orbit, the trajectories are adjusted so they can receive gravity-assists from the Moon. The gravity assist will send them both into heliocentric orbits, one spacecraft ahead of the Earth and the other behind the Earth. This trajectory was generated using a spacecraft ephemeris generated shortly after launch. |
| Completed |
2007-02-05 |
|
STEREO's Routes to Solar Orb
…
| Title |
STEREO's Routes to Solar Orbits |
| Abstract |
The two STEREO spacecraft, A (red path) and B (yellow path), are launched from the Earth into a highly eccentric orbit with an apogee that reaches the orbit of the Moon. Once in this orbit, the trajectories are adjusted so they can receive gravity-assists from the Moon. The gravity assist will send them both into heliocentric orbits, one spacecraft ahead of the Earth and the other behind the Earth. This trajectory was generated using a spacecraft ephemeris generated shortly after launch. |
| Completed |
2007-02-05 |
|
STEREO's Routes to Solar Orb
…
| Title |
STEREO's Routes to Solar Orbits |
| Abstract |
The two STEREO spacecraft, A (red path) and B (yellow path), are launched from the Earth into a highly eccentric orbit with an apogee that reaches the orbit of the Moon. Once in this orbit, the trajectories are adjusted so they can receive gravity-assists from the Moon. The gravity assist will send them both into heliocentric orbits, one spacecraft ahead of the Earth and the other behind the Earth. This trajectory was generated using a spacecraft ephemeris generated shortly after launch. |
| Completed |
2007-02-05 |
|
STEREO's Routes to Solar Orb
…
| Title |
STEREO's Routes to Solar Orbits |
| Abstract |
The two STEREO spacecraft, A (red path) and B (yellow path), are launched from the Earth into a highly eccentric orbit with an apogee that reaches the orbit of the Moon. Once in this orbit, the trajectories are adjusted so they can receive gravity-assists from the Moon. The gravity assist will send them both into heliocentric orbits, one spacecraft ahead of the Earth and the other behind the Earth. This trajectory was generated using a spacecraft ephemeris generated shortly after launch. |
| Completed |
2007-02-05 |
|
STEREO's Routes to Solar Orb
…
| Title |
STEREO's Routes to Solar Orbits |
| Abstract |
The two STEREO spacecraft, A (red path) and B (yellow path), are launched from the Earth into a highly eccentric orbit with an apogee that reaches the orbit of the Moon. Once in this orbit, the trajectories are adjusted so they can receive gravity-assists from the Moon. The gravity assist will send them both into heliocentric orbits, one spacecraft ahead of the Earth and the other behind the Earth. This trajectory was generated using a spacecraft ephemeris generated shortly after launch. |
| Completed |
2007-02-05 |
|
Solar Eclipse over Africa
| Title |
Solar Eclipse over Africa |
| Description |
Eastern Africa was cloaked in darkness when the Moderate Resolution Imaging Spectroradiometer (MODIS [ http://modis.gsfc.nasa.gov ]) on NASA's Aqua [ http://aqua.nasa.gov/ ] satellite caught this image on October 3, 2005. The inky blackness that covers much of Ethiopia, Kenya, Uganda, and parts of Sudan and the Democratic Republic of the Congo in this image was caused when the Moon crossed in front of the Sun in an annular solar eclipse. During such an eclipse, the Sun is visible as a fiery circle around the black disk of the moon. In the dimness beneath the Moon's shadow, very little light remained for MODIS to capture this image. Under normal conditions [ http://rapidfire.sci.gsfc.nasa.gov/subsets/?NAfrica_3_07/2005276 ], the land in the lower half of the image is a lush green, with patches of tan where the land is bare. Here, the tan areas have a red tint in the low light, while the green is completely black. Red dots show where fires were burning in vegetated areas. In the top half of the image, the orange of the Sahara desert is shown in darker tones than normal [ http://rapidfire.sci.gsfc.nasa.gov/subsets/?NAfrica_2_07/2005276 ]. Only in the upper right corner of the image, where full daylight has returned, does the desert look normal. Gradations of darkness within the shadowed area can be seen in the clouds. Bright white clouds reflect light well, so they are easily visible, even in the shadow. Since some light reached the Earth, the clouds remain bright along the outer edges of the shadowed region. As the eclipse progressed, the moon's shadow traveled southeast across the globe. When this image was taken, the deepest shadow lay over Kenya in the lower right corner of the image. Here the clouds are darker, an indication that there was less light to reflect back to the satellite. If this had been a total solar eclipse, the shadow cast by the moon would have been complete. The difference between a total solar eclipse and an annular eclipse is caused by the Moon's orbit around the Earth. The Moon's orbit is not circular, it is elliptical, like a squashed circle with the Earth at its center. This means that the Moon is not always the same distance from the Earth. When it is close to the Earth, the Moon appears larger than when it is far away. During a total solar eclipse, the Moon is closer to the Earth and so is able to block out the Sun entirely. An annular eclipse occurs when the Moon is farther from the Earth, and so the Moon's disk is not large enough to cover the Sun. The large image provided above has a resolution of 500 meters per pixel. It is available in additional resolutions from the MODIS Rapid Response Team. Tiny blue flecks in the large image are defects in the data. NASA image courtesy the MODIS Rapid Response Team [ http://rapidfire.sci.gsfc.nasa.gov ] at NASA GSFC. |
|
Total Solar Eclipse over Afr
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| Title |
Total Solar Eclipse over Africa and the Mediterranean |
| Description |
At 10:40 UTC (Coordinated Universal Time), NASA's Aqua [ http://aqua.nasa.gov ] satellite flew over the eastern Mediterranean as the shadow of the Moon traveled across Libya and the Mediterranean. As Aqua passed over, the Moderate Resolution Imaging Spectroradiometer (MODIS) [ http://modis.gsfc.nasa.gov ] captured the top image in this pair. The deep shadow cast by the Moon as it passed in front of the Sun is clearly visible on the Earth, in stark contrast to the daylight view of the same area captured just an hour earlier by the MODIS on the Terra [ http://terra.nasa.gov ] satellite. During the eclipse, clouds and snow were still visible, but the land surface below was lost in darkness. NASA images created by Jesse Allen, Earth Observatory, using data obtained courtesy of the MODIS Rapid Response team. |
|
Total Solar Eclipse over Afr
…
| Title |
Total Solar Eclipse over Africa and the Mediterranean |
| Description |
At 10:40 UTC (Coordinated Universal Time), NASA's Aqua [ http://aqua.nasa.gov ] satellite flew over the eastern Mediterranean as the shadow of the Moon traveled across Libya and the Mediterranean. As Aqua passed over, the Moderate Resolution Imaging Spectroradiometer (MODIS) [ http://modis.gsfc.nasa.gov ] captured the top image in this pair. The deep shadow cast by the Moon as it passed in front of the Sun is clearly visible on the Earth, in stark contrast to the daylight view of the same area captured just an hour earlier by the MODIS on the Terra [ http://terra.nasa.gov ] satellite. During the eclipse, clouds and snow were still visible, but the land surface below was lost in darkness. NASA images created by Jesse Allen, Earth Observatory, using data obtained courtesy of the MODIS Rapid Response team. |
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Total solar eclipse over Ant
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| Title |
Total solar eclipse over Antarctica |
| Description |
The moon cast a long shadow over Antarctica on November 23, 2003, in a total solar eclipse. The sun typically hangs low on the horizon during the southernmost continent's almost-summer months, so when the Moon moved between the Sun and the Earth, its shadow fell in a roughly 500-kilometer long oval like the long shadows of a early summer dawn. At the time this image was taken, the sun was at approximately 15 degrees above the horizon. The shadow's long circular shape is the same pattern a flashlight casts an the floor when held at a similar angle. The moon's shadow has two parts: the fuzzy outer shadow, the penumbra, and the dark inner shadow, the umbra. Within the umbra, the sun is completely blocked. A person standing on the ground sees a glowing black disk in front of the sun?the disk is the moon, and the glow is the sun's corona. In the penumbra, the ground observer sees the moon covering part of the sun. Both the penumbra and the umbra are visible in this true-color image. The Moderate Resolution Imaging Spectroradiometer [ http://modis.gsfc.nasa.gov ] (MODIS) on the Aqua [ http://aqua.nasa.gov/ ] satellite captured this image of the eclipse between 23:15 and 23:20 UTC. The Terra [ http://terra.nasa.gov/ ] satellite captured a similar image [ http://rapidfire.sci.gsfc.nasa.gov/gallery/?2003327-1123/Antarctica.A2003327.2255 ] of the eclipse. The eclipse started at 22:08 UTC, and the shadow passed from the surface of the earth a little over an hour later at 23:20 UTC. The sun's light was completely blocked at 22:49 for one minute and 55 seconds. At the time this image was taken, the sun was just rising over Antarctica, tinting the mountains a delicate pink, even within the shadow of the eclipse. Beyond the dark upper left corner, the sun has not yet driven away night's darkness. The bluish tones of the snow reveal how Antarctica appears from space without atmospheric correction. The shadow covers Queen Maud Land, Antarctica, with its tip pointing towards Africa. The South Pole is just beyond the right corner of the image. The moon is not the only thing throwing shadows across the landscape in this image. On the top left, the Pensacola Mountains make long horizontal shadows on the ice. Patches of low cloud along the left side of the umbra are also leaving a dark smudge on the surface. This image is available in multiple resolutions [ http://rapidfire.sci.gsfc.nasa.gov/gallery/?2003327-1123/Antarctica2.A2003327.2320 ]. Image courtesy Jacques Descloitres, MODIS Rapid Response Team [ http://rapidfire.sci.gsfc.nasa.gov ] at NASA GSFC |
|
Total solar eclipse over Ant
…
| Title |
Total solar eclipse over Antarctica |
| Description |
The moon cast a long shadow over Antarctica on November 23, 2003, in a total solar eclipse. The sun typically hangs low on the horizon during the southernmost continent's almost-summer months, so when the Moon moved between the Sun and the Earth, its shadow fell in a roughly 500-kilometer long oval like the long shadows of a early summer dawn. At the time this image was taken, the sun was at approximately 15 degrees above the horizon. The shadow's long circular shape is the same pattern a flashlight casts an the floor when held at a similar angle. The moon's shadow has two parts: the fuzzy outer shadow, the penumbra, and the dark inner shadow, the umbra. Within the umbra, the sun is completely blocked. A person standing on the ground sees a glowing black disk in front of the sun?the disk is the moon, and the glow is the sun's corona. In the penumbra, the ground observer sees the moon covering part of the sun. Both the penumbra and the umbra are visible in this true-color image. The Moderate Resolution Imaging Spectroradiometer [ http://modis.gsfc.nasa.gov ] (MODIS) on the Aqua [ http://aqua.nasa.gov/ ] satellite captured this image of the eclipse between 23:15 and 23:20 UTC. The Terra [ http://terra.nasa.gov/ ] satellite captured a similar image [ http://rapidfire.sci.gsfc.nasa.gov/gallery/?2003327-1123/Antarctica.A2003327.2255 ] of the eclipse. The eclipse started at 22:08 UTC, and the shadow passed from the surface of the earth a little over an hour later at 23:20 UTC. The sun's light was completely blocked at 22:49 for one minute and 55 seconds. At the time this image was taken, the sun was just rising over Antarctica, tinting the mountains a delicate pink, even within the shadow of the eclipse. Beyond the dark upper left corner, the sun has not yet driven away night's darkness. The bluish tones of the snow reveal how Antarctica appears from space without atmospheric correction. The shadow covers Queen Maud Land, Antarctica, with its tip pointing towards Africa. The South Pole is just beyond the right corner of the image. The moon is not the only thing throwing shadows across the landscape in this image. On the top left, the Pensacola Mountains make long horizontal shadows on the ice. Patches of low cloud along the left side of the umbra are also leaving a dark smudge on the surface. This image is available in multiple resolutions [ http://rapidfire.sci.gsfc.nasa.gov/gallery/?2003327-1123/Antarctica2.A2003327.2320 ]. Image courtesy Jacques Descloitres, MODIS Rapid Response Team [ http://rapidfire.sci.gsfc.nasa.gov ] at NASA GSFC |
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Earth, Moon, Hubble
| Title |
Earth, Moon, Hubble |
| Explanation |
The Space Shuttle Discovery Crew [ http://spaceflight.nasa.gov/shuttle/archives/sts-103/crew/ ] was fortunate enough to witness one of the brighter full moon's from orbit two weeks ago during their mission to fix the Hubble Space Telescope [ http://www.stsci.edu/hst/ ]. Pictured on the left [ http://spaceflight.nasa.gov/gallery/images/shuttle/sts-103/html/s103e5252.html ], the horizon of the Earth [ http://antwrp.gsfc.nasa.gov/apod/ap990619.html ] is visible below this full Moon [ http://antwrp.gsfc.nasa.gov/apod/ap991108.html ], which is below the edge of the Hubble Space Telescope [ http://antwrp.gsfc.nasa.gov/apod/ap970306.html ]. The full Moon on this day, last December 22 [ http://antwrp.gsfc.nasa.gov/apod/ap991222.html ], was a few percent brighter than average [ http://www.skypub.com/news/pr_991217brightmoon.html ] because it was full at nearly the same time it was at its closest to the Earth, which comes at a time when the Earth is relatively close to the Sun. The Shuttle Crew successfully showered [ http://spaceflight.nasa.gov/spacenews/reports/sts103/STS-103-13.html ] Hubble with needed holiday gifts, including six new gyroscopes [ http://hubble.gsfc.nasa.gov/sm3a_fact_sheets.html#gyroscopes ], a new computer [ http://hubble.gsfc.nasa.gov/sm3a_fact_sheets.html#advanced ], and new batteries [ http://www.howstuffworks.com/battery.htm ]. |
|
Eros Encounter Nears
| Title |
Eros Encounter Nears |
| Explanation |
After an unanticipated [ http://antwrp.gsfc.nasa.gov/apod/ap000205.html ] extra trip around the Sun, the NEAR spacecraft [ http://near.jhuapl.edu/ ] is now politely approaching [ http://near.jhuapl.edu/iod/000/index.html ] asteroid 433 [ http://near.jhuapl.edu/eros/history/too_many.html ], Eros [ http://near.jhuapl.edu/eros/history/ ], at a respectful relative speed of about 20 miles per hour. Still nearly 2,000 miles distant, NEAR will [ http://www.jhuapl.edu/public/pr/000208.htm ] close to within approximately 200 miles by February 14th - Valentine's Day. If all goes well, the spacecraft will then be captured by the gentle attraction of Eros' [ http://near.jhuapl.edu/eros/sum.html ] gravity, becoming the first artificial moon of an asteroid [ http://antwrp.gsfc.nasa.gov/apod/ap990807.html ]. While Eros is not round [ http://nearweb.jhuapl.edu/cgi-bin/ion-p?page=near_shape.html ] it is certainly not heart-shaped [ http://echo.jpl.nasa.gov/asteroids/433_Eros/eros.html ] either as seen in this series [ http://near.jhuapl.edu/iod/20000207/index.html ] of frames showing the roughly 20 x 8 x 8 mile asteroid during its 5.27 hour rotation period. Different [ http://www.seds.org/nineplanets/nineplanets/pxmisc.html#otherast ] perspectives clearly show a gouge or saddle and a large impact crater with a raised rim near the asteroid's [ http://www.boulder.swri.edu/~cchapman/finderos.html ] narrow waist. The frames were recorded by the NEAR spacecraft's multi-spectral imager [ http://near.jhuapl.edu/instruments/ ] on February 4th from a range of 4,600 miles. |
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Natural Saturn On The Cassin
…
| Title |
Natural Saturn On The Cassini Cruise |
| Explanation |
What could you see approaching Saturn [ http://www.jpl.nasa.gov/cassini/Kids/stories/ ] aboard an interplanetary cruise [ http://www.jpl.nasa.gov:80/cassini/Mission/cruise.html ] ship? Your view would likely resemble this subtly shaded image [ http://oposite.stsci.edu/pubinfo/pr/1998/28/b.html ] of the gorgeous ringed gas giant. Processed by the Hubble Heritage project [ http://heritage.stsci.edu/ ], the picture intentionally avoids overemphasizing color contrasts and presents a natural looking Saturn [ http://heritage.stsci.edu/ public/Oct22/saturn/saturntable.html#caption ] with cloud bands, storms [ http://antwrp.gsfc.nasa.gov/apod/ap951018.html ], nearly edge-on rings [ http://antwrp.gsfc.nasa.gov/apod/ap981018.html ], and the small round shadow of the moon Enceladus near the center of the planet's disk. Of course, seats were not available on the only ship currently enroute [ http://www.jpl.nasa.gov/cassini/ ] - the Cassini spacecraft, launched in 1997 [ http://antwrp.gsfc.nasa.gov/apod/ap971016.html ] and scheduled to arrive at Saturn [ http://www.jpl.nasa.gov/cassini/today/ ] in the year 2004. After an extended cruise to a world 1,400 million kilometers from the Sun [ http://antwrp.gsfc.nasa.gov/apod/ap960727.html ], Cassini will tour the Saturnian system [ http://www.hawastsoc.org/solar/eng/saturn.htm ], conducting a remote, robotic exploration with software and instruments designed by [ http://www.jpl.nasa.gov/cassini/Partners/ ] denizens of planet Earth. But where is Cassini now [ http://www.jpl.nasa.gov/cassini/today/ ]? Still about 980 million kilometers from Saturn, last Sunday the spacecraft flew by asteroid 2685 Masursky [ http://www.jpl.nasa.gov/cassini/MoreInfo/ sigevents/sigevent000128.html ]. |
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Solar Eclipse and SOHO
| Title |
Solar Eclipse and SOHO |
| Explanation |
Neither rain, nor snow, nor dark of night can keep the space-based SOlar Heliospheric Observatory (SOHO) from watching the Sun [ http://antwrp.gsfc.nasa.gov/apod/ap051201.html ]. In fact, from its vantage point 1.5 million kilometers sunward of planet Earth, SOHO's cameras can always monitor [ http://sohowww.nascom.nasa.gov/data/latestimages.html ] the Sun's outer atmosphere, or corona. But only during a total solar eclipse [ http://www.kidseclipse.com/pages/a1b3c1d0.htm ] can earth-based observers see the lovely coronal [ http://antwrp.gsfc.nasa.gov/apod/ap021213.html ] streamers and structures - when the Moon briefly blocks the overwhelmingly bright solar surface. In this composite view, SOHO's [ http://sohowww.nascom.nasa.gov/hotshots/ 2006_03_29/ ] uninterrupted view of the solar corona above the solar photosphere (center) and corona far beyond the Sun's disk, are shown in orange hues. The middle, donut-shaped region is the corona [ http://www.phy6.org/Education/wcorona.html ] as recorded by the Williams College Eclipse Expedition to Kastelorizo [ http://antwrp.gsfc.nasa.gov/apod/ap060330.html ] Island, Greece, headed by Jay Pasachoff, during the March 29th total solar eclipse [ http://spaceweather.com/eclipses/ gallery_29mar06_page3.htm ]. Merging ground [ http://antwrp.gsfc.nasa.gov/apod/ap031208.html ] and space-based [ http://antwrp.gsfc.nasa.gov/apod/ap020516.html ] views allows astronomers to trace features in the corona that reach from just above the Sun's surface into the solar wind [ http://www.phy6.org/Education/wsolwind.html ]. |
|
A Sun Halo over Utah
| Title |
A Sun Halo over Utah |
| Explanation |
Have you ever seen a halo around the Sun? This fairly common sight occurs when high thin clouds [ http://ww2010.atmos.uiuc.edu/(Gh)/wwhlpr/cirrus.rxml?hret=/guides/mtr/opt/ice/halo/22.rxml ] containing millions of tiny ice crystals [ http://www.sundog.clara.co.uk/halo/crystals.htm ] cover much of the sky. Each ice crystal [ http://en.wikipedia.org/wiki/Ice_crystal ] acts like a miniature lens. Because most [ http://www.sundog.clara.co.uk/halo/xtalreal.htm ] of the crystals have a similar elongated hexagonal shape, light entering one crystal face and exiting through the opposing face refracts 22 degrees [ http://mintaka.sdsu.edu/GF/explain/atmos_refr/angles.html ], which corresponds to the radius of the Sun Halo [ http://ww2010.atmos.uiuc.edu/(Gh)/guides/mtr/opt/ice/halo/22.rxml ]. A similar Moon Halo [ http://antwrp.gsfc.nasa.gov/apod/ap030321.html ] may be visible during the night. The picture was taken in Gunlock, Utah [ http://en.wikipedia.org/wiki/Utah ], USA [ http://www.cia.gov/cia/publications/factbook/geos/us.html ]. A flock of birds [ http://www.straightdope.com/mailbag/mflockswoop.html ] was caught by chance in the foreground. Exactly how ice-crystals form [ http://www.its.caltech.edu/~atomic/snowcrystals/primer/primer.htm ] in clouds remains under investigation [ http://adsabs.harvard.edu/cgi-bin/nph-bib_query?bibcode=1995dri..rept.....H ]. |
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A Lunar Eclipse Over Time
| Title |
A Lunar Eclipse Over Time |
| Explanation |
During last week's lunar eclipse [ http://sunearth.gsfc.nasa.gov/eclipse/SEextra/TLE2000Jan20.html ], our Moon [ http://www.seds.org/nineplanets/nineplanets/luna.html ] appeared to disappear. As the Earth moved between the Moon and the Sun, the Earth's shadow fell on the moon, making it quite dark [ http://antwrp.gsfc.nasa.gov/apod/ap970110.html ]. In the above photograph, the Earth's rotation caused the Moon and stars to appear as streaks [ http://antwrp.gsfc.nasa.gov/apod/ap980912.html ] during this four-hour exposure. In the foreground is the abbey of the Benedictive monastery of Sant Llorenc del Munt [ http://www.culturamatadepera.es/tpobl01a.htm ], a structure in Girona, Spain that has stood since the eleventh century. As the Earth's shadow engulfed the Moon [ http://sunearth.gsfc.nasa.gov/eclipse/LEcat/LEcatalog.html ], the Moon streak became less and less bright, practically disappearing during totality [ http://antwrp.gsfc.nasa.gov/apod/ap960926.html ]. At this time, the Moon, which normally shines by reflecting direct sunlight, shone only by sunlight refracted [ http://www.geom.umn.edu/education/calc-init/rainbow/refraction.html ] through the Earth's atmosphere [ http://csep10.phys.utk.edu/astr161/lect/earth/atmosphere.html ]. Later, clouds obscured the re-appearing Moon. |
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Southwest Mercury
| Title |
Southwest Mercury |
| Explanation |
The planet Mercury resembles a moon. Mercury [ http://www.seds.org/nineplanets/nineplanets/mercury.html ]'s old surface is heavily cratered [ http://liftoff.msfc.nasa.gov/Academy/SPACE/SolarSystem/Meteors/Craters.html ] like many moons. Mercury [ http://www.solarviews.com/eng/mercury.htm ] is larger than most moons but smaller than Jupiter [ http://antwrp.gsfc.nasa.gov/apod/ap990806.html ]'s moon Ganymede [ http://antwrp.gsfc.nasa.gov/apod/ap990304.html ] and Saturn [ http://antwrp.gsfc.nasa.gov/apod/ap960717.html ]'s moon Titan [ http://antwrp.gsfc.nasa.gov/apod/ap990207.html ]. Mercury is much denser and more massive than any moon, though, because it is made mostly of iron. In fact, the Earth [ http://antwrp.gsfc.nasa.gov/apod/ap990131.html ] is the only planet more dense. A visitor to Mercury's surface [ http://antwrp.gsfc.nasa.gov/apod/ap960121.html ] would see some strange sights. Because Mercury [ http://www.oulu.fi/~spaceweb/textbook/mercury.html ] rotates exactly three times every two orbits around the Sun [ http://antwrp.gsfc.nasa.gov/apod/ap951004.html ], and because Mercury [ http://nssdc.gsfc.nasa.gov/photo_gallery/photogallery-mercury.html ]'s orbit is so elliptical, a visitor to Mercury [ http://antwrp.gsfc.nasa.gov/apod/ap990102.html ] might see the Sun [ http://antwrp.gsfc.nasa.gov/htmltest/gifcity/interv.html ] rise, stop in the sky, go back toward the rising horizon [ http://antwrp.gsfc.nasa.gov/apod/ap990619.html ], stop again, and then set quickly over the other horizon. From Earth [ http://antwrp.gsfc.nasa.gov/apod/ap980530.html ], Mercury's proximity to the Sun [ http://antwrp.gsfc.nasa.gov/apod/ap981212.html ] cause it to be visible only for a short time just after sunset or just before sunrise. |
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A Total Solar Eclipse over T
…
| Title |
A Total Solar Eclipse over Turkey |
| Explanation |
Some views [ http://spaceweather.com/eclipses/gallery_29mar06.htm ] of last week's total eclipse [ http://en.wikipedia.org/wiki/Total_eclipse ] of the Sun were better than others. One spectacular view [ http://antwrp.gsfc.nasa.gov/apod/ap060331.html ] occurred over Adrasan (near Antalya [ http://en.wikipedia.org/wiki/Antalya ]), Turkey [ http://en.wikipedia.org/wiki/Turkey ] and was captured there by industrious astrophotographer Stefan Seip. The above digital mosaic [ http://www.photomeeting.de/astromeeting/sun/060329sofi_d1024.htm ] caught the Moon in several stages as it moved between the Earth and the Sun. During the center frame, a total solar eclipse [ http://www.mreclipse.com/Special/SEprimer.html ] was visible, the Moon completely blocked the Sun, the area became dark, and the magnificent corona [ http://antwrp.gsfc.nasa.gov/apod/ap010408.html ] of the Sun became visible. The foreground frame from the same location was taken during sunlight. The next total eclipse [ http://mreclipse.com/Special/SEnext.html ] of the Sun will occur in August 2008 and be visible from parts of North America [ http://www.cia.gov/cia/publications/factbook/reference_maps/north_america.html ], Europe [ http://antwrp.gsfc.nasa.gov/apod/ap030324.html ], and Asia [ http://en.wikipedia.org/wiki/Asia ]. |
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Animation of Asteroids Passi
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| Title |
Animation of Asteroids Passing Near Earth |
| Explanation |
How often does an asteroid whiz by the Earth? The above time-lapse animation [ http://cfa-www.harvard.edu/iau/Animations/Animations.html ] follows the orbit of the Earth around the Sun for two months in 2002 as numerous asteroids [ http://en.wikipedia.org/wiki/Asteroids ], also known as minor planets [ http://en.wikipedia.org/wiki/Minor_planet ], approach and pass by. Some asteroids appear out of nowhere [ http://antwrp.gsfc.nasa.gov/apod/ap041001.html ] as they are plotted only when they were discovered. Most asteroids plotted were discovered only [ http://antwrp.gsfc.nasa.gov/apod/ap040322.html ] during the previous year. Although none of the plotted objects came inside the orbit of our Moon, our Solar System is filled with objects [ http://antwrp.gsfc.nasa.gov/apod/ap050417.html ] as small as bits of sand, usually left by a comet, that appear as meteors as they streak into the Earth's atmosphere every day. The only objects displayed are those visible from Earth [ http://antwrp.gsfc.nasa.gov/apod/ap050102.html ] closer than 20 million kilometers, color coded by three-dimensional distance. In comparison, the Earth is a relatively small target having a radius of about 6,400 kilometers. One significant research area [ http://pan-starrs.ifa.hawaii.edu/public/asteroid-threat/asteroid_threat.html ] in modern astronomy involves trying to find the majority of asteroids that could pose a future collision threat [ http://neo.jpl.nasa.gov/risk/ ] with Earth. |
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Crumbling Comet Schwassmann-
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| Title |
Crumbling Comet Schwassmann-Wachmann 3 Approaches |
| Explanation |
A crumbling comet will soon pass near the Earth. Comet 73P/Schwassmann-Wachmann 3 [ http://science.nasa.gov/headlines/y2006/24mar_73p.htm ] is brightening and may even be visible to the unaided eye [ http://webvision.med.utah.edu/anatomy.html ] when the fragmented comet [ http://antwrp.gsfc.nasa.gov/apod/ap040724.html ] zooms past Earth during the middle of next month. Still, the small comet poses no Earth hazard [ http://liftoff.msfc.nasa.gov/Academy/SPACE/SolarSystem/Meteors/ImpactHazard.html ], since it will pass the Earth at about 25 times the distance of the Moon. Exactly how bright Comet Schwassman-Wachmann 3 [ http://en.wikipedia.org/wiki/73P/Schwassmann-Wachmann ] will get is unknown. It is even possible, althought unlikely, that debris from the comet [ http://cometography.com/pcomets/073p.html ] will have spread out enough to cause a notable meteor shower [ http://antwrp.gsfc.nasa.gov/apod/ap031116.html ]. Pictured above [ http://www.eso.org/outreach/press-rel/pr-2006/phot-15-06.html ], Fragment B of Comet Schwassman-Wachmann 3 [ http://www.eso.org/outreach/press-rel/pr-2006/pr-15-06.html ] was photographed two nights ago by a 8.2-meter Very Large Telescope [ http://antwrp.gsfc.nasa.gov/apod/ap990309.html ] in Chile [ http://en.wikipedia.org/wiki/Chile ]. Visible [ http://antwrp.gsfc.nasa.gov/apod/ap060426.html http://www.space.com/spacewatch/060414_night_sky.html ] to the lower right of the large B fragment are many mini-comets that have broken off and now orbit the Sun separately. Each mini-comet itself sheds gas and dust and so appears to have its own hazy coma. The comet [ http://skyandtelescope.com/observing/objects/comets/article_1704_1.asp ] will pass closest to the Sun on June 7. |
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Venus, Moon, and Neighbors
| Title |
Venus, Moon, and Neighbors |
| Explanation |
Rising before the Sun on February 2nd, astrophotographer [ http://pages.prodigy.net/pam.orman/JoeGallery.html ] Joe Orman anticipated [ http://pages.prodigy.net/pam.orman/JoeAlmanac2000.html ] this apparition of the bright morning star [ http://ispec.scibernet.com/station/morn_star.html ] Venus near a lovely crescent Moon above a neighbor's house in suburban Phoenix, Arizona, USA. Fortunately, the alignment of bright planets and the Moon is one of the most inspiring sights in the night sky [ http://www.skypub.com/sights/skyevents/0004skyevents.html ] and one that is often easy to enjoy and share without any special equipment. Take tonight [ http://spacescience.com/headlines/y2000/ast30mar_1m.htm ], for example. Those blessed with clear skies can simply step outside near sunset and view a young crescent Moon very near three bright planets in the west Jupiter [ http://galileo.jpl.nasa.gov/ ], Mars [ http://mars.jpl.nasa.gov/mgs/ ], and Saturn [ http://www.jpl.nasa.gov/cassini/ ]. Jupiter will be the unmistakable brightest star near the Moon with a reddish Mars just to Jupiter's north and pale yellow Saturn directly above. Of course, these sky shows [ http://drumright.ossm.edu/astronomy/conjunctions.html ] create an evocative picture [ http://antwrp.gsfc.nasa.gov/apod/ap000310.html ] but the planets and Moon just appear to be near each other -- they are actually only approximately lined up and lie in widely separated orbits. Unfortunately, next month's highly publicized alignment of planets [ http://www.griffithobs.org/SkyAlignments.html ] on May 5th will be lost from view in the Sun's glare but such planetary alignments [ http://www.skypub.com/news/special/whypanic.html ] occur repeatedly and pose no danger [ http://www.badastronomy.com/bad/misc/planets.html ] to planet Earth. |
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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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Planets Above The Clouds
| Title |
Planets Above The Clouds |
| Explanation |
Clouds scatter the faint orange rays of the setting sun [ http://antwrp.gsfc.nasa.gov/apod/ap000115.html ] in the foreground of this breathtaking photograph from the summit [ http://www.ifa.hawaii.edu/mko/mko.html ] of Mauna Kea, Hawaii [ http://antwrp.gsfc.nasa.gov/apod/ap980725.html ]. Taken on April 7th, this skyscape features a dramatic lunar and planetary alignment [ http://antwrp.gsfc.nasa.gov/apod/ap000406.html ]. An overexposed crescent moon [ http://antwrp.gsfc.nasa.gov/apod/ap991108.html ] dominates the celestial scene, but the bright "star" just below and to its right is Saturn [ http://www.jpl.nasa.gov/cassini/Kids/stories/ ] while further below Saturn is a close pairing of brilliant Jupiter [ http://antwrp.gsfc.nasa.gov/apod/ap000429.html ] and a fainter, yellowish Mars [ http://marsnt3.jpl.nasa.gov/education/students.html ]. Red giant star Aldebaran [ http://www.bo.astro.it/copernic/alde-eng.html ] is almost directly above the moon near the top of the image and the bright blue stars of the Pleiades cluster [ http://www.aao.gov.au/images.html/captions/uks018.html ] are visible about midway up and to the right of the moon-Aldebaran line. The good news is that planetary alignments [ http://www.skypub.com/news/special/whypanic.html ] like this one do not portend [ http://tech-two.mit.edu/Shakespeare/Tragedy/macbeth/ macbeth.html ] disasters, are relatively common, and can clearly make inspirational viewing for casual stargazers and astronomers alike. The bad [ http://www.badastronomy.com/bad/misc/planets.html ] news is that the world is not going to end because of the highly publicized planetary alignment [ http://www.griffithobs.org/SkyAlignments.html ] occurring tomorrow, May 5th -- so you probably will have to go to work [ http://www.nasa.gov/newsinfo/alignment.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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Comet Schwassmann-Wachmann 3
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| Title |
Comet Schwassmann-Wachmann 3 Passes the Earth |
| Explanation |
Rarely does a comet pass this close to Earth. Last week, dedicated astrofilmographers were able to take advantage of the close approach of crumbling 73P / Comet Schwassmann-Wachmann 3 [ http://en.wikipedia.org/wiki/Comet_73P ] to make time-lapse movies of the fast-moving comet. Large comet fragments passed about 25 times the Moon's distance from the Earth. The above time lapse movie of Fragment B [ http://antwrp.gsfc.nasa.gov/apod/ap060504.html ] of Comet Schwassmann-Wachmann 3 [ http://antwrp.gsfc.nasa.gov/apod/ap060511.html ] over Colorado [ http://en.wikipedia.org/wiki/Colorado ], USA [ http://www.cia.gov/cia/publications/factbook/geos/us.html ] was taken during a single night, May 16, with 83 consecutive 49-second exposures. Some observers report being able to perceive the slight motion of the comet with respect to the background stars using only their binoculars [ http://www.yesmag.bc.ca/Questions/binoculars.html ] and without resorting to the creation of fancy digital time-lapse movies. Fragment B of Comet Schwassmann-Wachmann 3 [ http://www.eso.org/outreach/press-rel/pr-2006/pr-15-06.html ] became just barely visible to the unaided eye two weeks ago but now is appearing to fade as the comet has moved past the Earth and nears the Sun. Many sky enthusiasts [ http://antwrp.gsfc.nasa.gov/apod/ap040808.html ] will be on the watch for a particularly active meteor shower tonight as the Earth made its closest approach to orbit of Comet Schwassmann-Wachmann 3 [ http://skyandtelescope.com/observing/objects/comets/article_1704_1.asp ] late yesterday. |
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The Belt of Venus over the V
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| Title |
The Belt of Venus over the Valley of the Moon |
| Explanation |
Although you've surely seen it, you might not have noticed it. During a cloudless twilight [ http://www.hyperdictionary.com/dictionary/twilight ], just before sunrise [ http://antwrp.gsfc.nasa.gov/apod/ap030320.html ] or after sunset [ http://antwrp.gsfc.nasa.gov/apod/ap030412.html ], part of the atmosphere above the horizon appears slightly off-color, slightly pink. Called the Belt of Venus [ http://www.weather-photography.com/Photos/gallery.php?cat=optics&subcat=venus_belt ], this off-color band between the dark eclipsed [ http://antwrp.gsfc.nasa.gov/apod/ap030822.html ] sky and the blue sky [ http://www.sciencemadesimple.com/sky_blue.html ] can be seen in nearly every direction including that opposite the Sun. Straight above, blue sky [ http://www.why-is-the-sky-blue.org/why-is-the-sky-blue.html ] is normal sunlight reflecting off the atmosphere. In the Belt of Venus [ http://epod.usra.edu/archive/epodviewer.php3?oid=158080 ], however, the atmosphere reflects light from the setting (or rising) Sun which appears more red. The Belt of Venus [ http://en.wikipedia.org/wiki/Belt_of_Venus ] can be seen from any location with a clear horizon. Pictured above, the Belt of Venus was photographed above morning fog [ http://antwrp.gsfc.nasa.gov/apod/ap021122.html ] in the Valley of the Moon [ http://www.vmoa.kenwood.ca.us/ ], a famous wine-producing region in northern California [ http://en.wikipedia.org/wiki/California ], USA [ http://www.cia.gov/cia/publications/factbook/geos/us.html ]. The belt is frequently [ http://antwrp.gsfc.nasa.gov/apod/ap011209.html ] caught [ http://antwrp.gsfc.nasa.gov/apod/ap010601.html ] by [ http://antwrp.gsfc.nasa.gov/apod/ap010308.html ] accident [ http://antwrp.gsfc.nasa.gov/apod/ap990418.html ] in [ http://antwrp.gsfc.nasa.gov/apod/ap990325.html ] other [ http://antwrp.gsfc.nasa.gov/apod/ap990308.html ] photographs [ http://antwrp.gsfc.nasa.gov/apod/ap010501.html ]. |
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Crescent Rhea Occults Cresce
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| Title |
Crescent Rhea Occults Crescent Saturn |
| Explanation |
Soft hues, partially lit orbs, a thin trace of the ring, and slight shadows highlight this understated view of the majestic surroundings of the giant planet Saturn. Looking nearly back toward the Sun, the robot Cassini spacecraft [ http://en.wikipedia.org/wiki/Cassini-Huygens ] now orbiting Saturn captured crescent phases [ http://antwrp.gsfc.nasa.gov/apod/ap060618.html ] of Saturn [ http://www.nineplanets.org/saturn.html ] and its moon Rhea [ http://antwrp.gsfc.nasa.gov/apod/ap060530.html ] in color a few months ago. As striking as the above image [ http://photojournal.jpl.nasa.gov/catalog/PIA07806 ] is, it is but a single frame from a recently released 60-frame silent movie where Rhea can be seen gliding in front of its parent world. Since Cassini was nearly in the plane of Saturn's rings [ http://pds-rings.seti.org/saturn/ ], the normally impressive rings are visible here only as a thin line [ http://antwrp.gsfc.nasa.gov/apod/ap051219.html ] across the image center. Cassini has now passed the official half-way mark of its mission around Saturn, but is well situated to complete another two years [ http://saturn.jpl.nasa.gov/news/press-release-details.cfm?newsID=670 ] investigating this complex and surprising system. |
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Planets In The Sun
| Title |
Planets In The Sun |
| Explanation |
Today [ http://science.nasa.gov/headlines/y2000/ast02may_1.htm ], all five naked-eye planets [ http://www.seds.org/nineplanets/nineplanets/ ] (Mercury, Venus, Mars, Jupiter, Saturn) plus the Moon and the Sun [ http://helios.gsfc.nasa.gov/ sun.html ] will at least approximately line-up. As viewed [ http://drumright.ossm.edu/astronomy/conjunctions.html ] from planet Earth, they will be clustered within about 26 degrees, the closest alignment for all these celestial bodies [ http://science.nasa.gov/headlines/y2000/ ast30mar_1m.htm#alignments ] since February 1962, when there was a solar eclipse [ http://antwrp.gsfc.nasa.gov/apod/ap990818.html ]! Such planetary alignments [ http://www.griffithobs.org/SkyAlignments.html ] are not dangerous, except of course that the Sun might hurt your eyes when you look at it [ http://antwrp.gsfc.nasa.gov/apod/ap981212.html ]. So it might be easier [ http://sohowww.nascom.nasa.gov/hotshots/ ] to appreciate today's solar system [ http://space.jpl.nasa.gov/ ] spectacle if |
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A Halo Around the Moon
| Title |
A Halo Around the Moon |
| Explanation |
Have you ever seen a halo around the Moon? This fairly common sight occurs when high thin clouds [ http://ww2010.atmos.uiuc.edu/(Gh)/wwhlpr/cirrus.rxml?hret=/guides/mtr/opt/ice/halo/22.rxml ] containing millions of tiny ice crystals [ http://dspace.dial.pipex.com/lc/halo/crystals.htm ] cover much of the sky. Each ice crystal [ http://kristall.uni-mki.gwdg.de/homep1.htm ] acts like a miniature lens. Because most [ http://dspace.dial.pipex.com/lc/halo/xtalreal.htm ] of the crystals have a similar elongated hexagonal shape, light entering one crystal face and exiting through the opposing face refracts 22 degrees, which corresponds to the radius of the Moon Halo [ http://ww2010.atmos.uiuc.edu/(Gh)/guides/mtr/opt/ice/halo/22.rxml ]. A similar Sun Halo [ http://antwrp.gsfc.nasa.gov/apod/ap990823.html ] may be visible during the day. The town in the foreground of the above picture [ http://www.skylook.net/album/fenatm/fat3i.htm ] is San Sebastian [ http://www.donsnsn.es/icaste.htm ], Spain [ http://www.odci.gov/cia/publications/factbook/sp.html ]. The distant planet Jupiter [ http://antwrp.gsfc.nasa.gov/apod/jupiter.html ] appears by chance on the halo [ http://dspace.dial.pipex.com/lc/halo/halfeat.htm ]'s upper right. Exactly how ice-crystals form [ http://www.public.iastate.edu/~skrentz/ice_crystal.htm ] in clouds remains under investigation [ http://adsabs.harvard.edu/cgi-bin/nph-bib_query?bibcode=1995dri..rept.....H ]. |
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Ganymede: The Largest Moon i
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| Title |
Ganymede: The Largest Moon in the Solar System |
| Explanation |
If Ganymede orbited the Sun, it would be considered a planet. The reason is that Jupiter [ http://galileo.jpl.nasa.gov/jupiter/jupiter.html ]'s moon Ganymede [ http://www.seds.org/nineplanets/nineplanets/ganymede.html ] is not only the largest moon in the Solar System [ http://www.seds.org/nineplanets/nineplanets/datamax.html ], it is larger than planets Mercury [ http://www.seds.org/nineplanets/nineplanets/mercury.html ] and Pluto [ http://dosxx.colorado.edu/plutohome.html ]. The robot spacecraft Galileo [ http://www.jpl.nasa.gov/galileo/overview.html ] currently orbiting Jupiter [ http://www.seds.org/nineplanets/nineplanets/jupiter.html ] has been able to zoom by Ganymede [ http://www.solarviews.com/eng/ganymede.htm ] several times and snap many close-up pictures. Ganymede, shown above [ http://photojournal.jpl.nasa.gov/cgi-bin/PIAGenCatalogPage.pl?PIA00716 ] in its natural colors, sports a large oval dark region known as Galileo Regio [ http://www.jpl.nasa.gov/galileo/ganymede/121896.html ]. In general, the dark regions on Ganymede [ http://sse.jpl.nasa.gov/features/planets/jupiter/ganymede.html ] are heavily cratered, implying they are very old, while the light regions are younger and dominated by unusual grooves [ http://antwrp.gsfc.nasa.gov/apod/ap960711.html ]. The origin of the grooves is still under investigation [ http://adsabs.harvard.edu/cgi-bin/nph-bib_query?bibcode=1998Icar..135..317P ]. |
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