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Sun and Earth of Jet Propulsion Laboratory (JPL) and Goddard Space Flight Center (GSFC)
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SOHO Watches Saturn and Cass
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| Description |
SOHO Watches Saturn and Cassini Pass Behind the Sun |
| Full Description |
In this SOHO image taken July 21, 2005, the Sun is represented by the white circle in the center. Saturn is the bright object to the left of the Sun. Interestingly, the streak accompanying Saturn is not the rings but a distortion caused by Saturn's brightness. Saturn is approaching "superior conjunction," that is, it will be almost directly behind the Sun from Earth -- thus the Cassini spacecraft, in orbit around Saturn, will not be able to send or receive transmissions normally. Regular science data collection has been temporarily suspended. As Cassini passes closest by the limb (edge) of the Sun on July 24 PDT, communications will be impossible because of the Sun's radio noise. The spacecraft will regain full communication with Earth on July 27, once again returning Saturn science data. In the meantime, controllers are sending approximately 100 commands per day to test communication status. Cassini radio scientists are taking advantage of this opportunity to study the Sun's corona from its effects on the radio signals that reach Earth. SOHO (Solar and Heliospheric Observatory Satellite) orbits the Sun parked in one of the five gravitational-neutral spots, called Lagrange Points. This specific spot, called L1, stays in the same place relative to the Sun and the Earth, offering a continuously uninterrupted view of the Sun. Saturn is not in sight again until the evening of July 24. After that date, it will be to the RIGHT of the sun. For more information on "superior conjunction," visit: http://www.jpl.nasa.gov/basics/bsf1-2.html#conj . For more information on the Lagrange Points, visit: http://map.gsfc.nasa.gov/m_mm/ob_techorbit1.html For more information on SOHO, visit: http://sohowww.nascom.nasa.gov/ . Finally, the latest SOHO images are available at: http://sohowww.nascom.nasa.gov/data/realtime/c3/1024/latest.gif . Credit: SOHO -- http://sohowww.nascom.nasa.gov/ |
| Date |
July 22, 2005 |
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SOHO Watches Saturn and Cass
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| Description |
SOHO Watches Saturn and Cassini Pass Behind the Sun |
| Full Description |
In this SOHO image taken July 21, 2005, the Sun is represented by the white circle in the center. Saturn is the bright object to the left of the Sun. Interestingly, the streak accompanying Saturn is not the rings but a distortion caused by Saturn's brightness. Saturn is approaching "superior conjunction," that is, it will be almost directly behind the Sun from Earth -- thus the Cassini spacecraft, in orbit around Saturn, will not be able to send or receive transmissions normally. Regular science data collection has been temporarily suspended. As Cassini passes closest by the limb (edge) of the Sun on July 24 PDT, communications will be impossible because of the Sun's radio noise. The spacecraft will regain full communication with Earth on July 27, once again returning Saturn science data. In the meantime, controllers are sending approximately 100 commands per day to test communication status. Cassini radio scientists are taking advantage of this opportunity to study the Sun's corona from its effects on the radio signals that reach Earth. SOHO (Solar and Heliospheric Observatory Satellite) orbits the Sun parked in one of the five gravitational-neutral spots, called Lagrange Points. This specific spot, called L1, stays in the same place relative to the Sun and the Earth, offering a continuously uninterrupted view of the Sun. Saturn is not in sight again until the evening of July 24. After that date, it will be to the RIGHT of the sun. For more information on "superior conjunction," visit: http://www.jpl.nasa.gov/basics/bsf1-2.html#conj . For more information on the Lagrange Points, visit: http://map.gsfc.nasa.gov/m_mm/ob_techorbit1.html For more information on SOHO, visit: http://sohowww.nascom.nasa.gov/ . Finally, the latest SOHO images are available at: http://sohowww.nascom.nasa.gov/data/realtime/c3/1024/latest.gif . Credit: SOHO -- http://sohowww.nascom.nasa.gov/ |
| Date |
July 22, 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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Hubble Follows Rapid Changes
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Hubble Follows Rapid Changes in Jupiter's Aurora |
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Spitzer and Hubble Capture E
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Spitzer and Hubble Capture Evolving Planetary Systems |
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Spitzer and Hubble Capture E
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Spitzer and Hubble Capture Evolving Planetary Systems |
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Spitzer and Hubble Capture E
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Spitzer and Hubble Capture Evolving Planetary Systems |
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A Summer View of Russia's Le
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| Title |
A Summer View of Russia's Lena Delta and Olenek River |
| Description |
These views of the Russian Arctic were acquired by NASA's Multi-angle Imaging SpectroRadiometer (MISR) instrument on July 11, 2004. The brief arctic summer had transformed the frozen tundra and the thousands of lakes, channels, and rivers of the Lena Delta into a fertile wetland, and the usual blanket of thick snow had melted from the vast plains and taiga forests. The images show an area in the northern part of the Sakha Republic in eastern Siberia. The Olenek River wends northeast from the bottom of the images to the upper left, and the delta through which the mighty Lena River empties into the Laptev Sea dominate the top portions of the images. Creating accurate maps of vegetation structure is essential for understanding the seasonal exchanges of energy and water at the Earth's surface and for preserving biodiversity. The left-hand image is a natural-color image from MISR's nadir (vertical-viewing) camera, in which the rivers appear murky due to sediment, and photosynthetically active vegetation appears green. The center image is also from MISR's nadir camera, but is a false-color view in which the predominant red color is due to the brightness of vegetation at near-infrared wavelengths. Apart from the Lena Delta, the most photosynthetically active regions are within the lower half of the image and throughout the great stretch of land that curves across the Olenek River.  The relatively barren ranges of the Volyoi Mountains appear as the pale tan-colored area to the right of image center. The right-hand image is a multiangle, false-color view made from the red band data of the 60-degree-backward, nadir, and 60-degree-forward cameras, displayed as red, green and blue, respectively. Water appears blue in this image because sun glint makes smooth, wet surfaces look brighter at the forward camera's view angle. Much of the landscape and many low clouds appear purple because these surfaces are both forward and backward scattering, and clouds that are further from the surface appear in a different spot for each view angle, creating a rainbow-like appearance. The highly vegetated region in the natural-color nadir image exhibits a faint greenish hue in the multi-angle composite. This subtle effect suggests that the nadir camera is observing more of the brighter, underlying surface than the oblique cameras, providing information about the distribution and density of trees and shrubs in this area. The Multiangle Imaging SpectroRadiometer observes the daylit Earth continuously, and every 9 days views the entire globe between 82 degrees north and 82 degrees south latitude. The MISR Browse Image Viewer [ http://earthobservatory.nasa.gov/cgi-bin/redirect?http://eosweb.larc.nasa.gov/MISRBR/ ], provides access to low-resolution true-color versions of these images. These data products were generated from a portion of the imagery acquired during Terra orbit 24273. The panels cover an area of about 230 kilometers x 420 kilometers, and utilize data from blocks 30 to 34 within World Reference System-2 path 134. MISR was built and is managed by NASA's Jet Propulsion Laboratory, Pasadena, CA, for NASA's Office of Earth Science, Washington, DC. The Terra satellite is managed by NASA's Goddard Space Flight Center, Greenbelt, MD. JPL is a division of the California Institute of Technology. Image courtesy NASA/GSFC/LaRC/JPL, MISR Team. [ http://www-misr.jpl.nasa.gov/ ] Text by Clare Averill (Raytheon/JPL). |
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Global, Seasonal Surface Alb
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Global, Seasonal Surface Albedos |
| Description |
Global models of the Earth system need accurate measurements of how much solar energy is reflected and absorbed by surfaces because this energy drives processes such as plant photosynthesis, snow melt, and longwave reradiation. These images from the Multi-angle Imaging SpectroRadiometer (MISR) provide global, seasonal summaries of a quantity called the Directional Hemispherical Reflectance (DHR), also sometimes referred to as the "black-sky" albedo. The amount of sunlight reflected from a surface, relative to the incident amount, is called the albedo. Bright surfaces have albedo near unity, and dark surfaces have albedo near zero. The DHR refers to the amount of spectral radiation reflected into all upward directions through an imaginary hemisphere situated above each surface point. The "directional" part of the name describes how, in the absence of an intervening atmosphere, light from the Sun would illuminate the surface from a single direction (that is, there is no diffuse skylight, hence the name "black-sky" albedo). To generate this product accurately, it is necessary to compensate for the effects of the atmosphere, and MISR's multi-angle retrieval techniques are used to screen clouds and account for the light scattered by airborne particulates (aerosols). The four image panels show DHR as it was retrieved over land surfaces in MISR's red, green, blue spectral bands (left), and near-infrared, red, blue spectral bands (right), for the seasonal periods December 2001 through February 2002 (top), and June 2002 through August 2002 (bottom). A one-year movie is also provided. Since relatively little sunlight reaches the polar regions during winter, the images were cropped to include only the area which is illuminated in both hemispheres during winter and summer. Noteworthy features include seasonal vegetation and the advance and retreat of the snow line. Regions where DHR could not be derived, either due to an inability to retrieve the necessary atmospheric characteristics or due to the presence of clouds, are shown in black. Further global summaries of the DHR (and other surface and vegetation products) from MISR are now available at the NASA Langley Atmospheric Sciences Data Center. [ http://eosweb.larc.nasa.gov/ ] The Multi-angle Imaging SpectroRadiometer observes the daylit Earth continuously from pole to pole, and every 9 days views the entire globe between 82 degrees north and 82 degrees south latitude. Image courtesy NASA/GSFC/LaRC/JPL, MISR Team. [ http://earthobservatory.nasa.gov/cgi-bin/redirect?http://www-misr.jpl.nasa.gov/ ] Text by Clare Averill (Acro Service Corporation/JPL) and David J. Diner (JPL). |
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Dewatering Effects from the
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Dewatering Effects from the Gujarat Earthquake |
| Description |
MISR Browse Image Viewer [ http://earthobservatory.nasa.gov/cgi-bin/redirect?http://eosweb.larc.nasa.gov/MISRBR/ ] provides access to low-resolution true-color versions of these images. This data product was generated from a portion of the imagery acquired during Terra orbits 5736 and 5969. The full-size images cover an area of 215 kilometers x 156 kilometers, and utilize data from blocks 71 to 72 within World Reference System-2 path 151. Image courtesy NASA/GSFC/LaRC/JPL, MISR Team. [ http://earthobservatory.nasa.gov/cgi-bin/redirect?http://www-misr.jpl.nasa.gov/ ] Text by Clare Averill (Acro Service Corporation/JPL) and David J. Diner (JPL)., browse image of orbit 5969 (380 KB JPEG) On January 26, 2001, when India's Republic Day is normally celebrated, a devastating earthquake hit the state of Gujarat. About 20,000 people died and millions were injured throughout the region. The earthquake had a magnitude of 7.7 on the Richter scale. After the earthquake, local residents reported a mixture of water and sediments fountaining from the Earth. These effects, referred to as dewatering, can result from intense ground shaking by strong earthquakes in regions with shallow water tables. Scientists initially observed dewatering in parts of the Rann of Kutch (a large salt pan in northern Gujarat), and in areas close to the earthquake epicenter. Recent research utilizes the unique capabilities of the Multi-angle Imaging SpectroRadiometer (MISR) instrument to observe earthquake-related dewatering over a broader area (related story: NASA Satellite Helps Scientists See Effects of Earthquakes in Remote Areas [ http://earthobservatory.nasa.gov/Newsroom/NasaNews/2003/2003020511146.html ]). This research is published in the February 4, 2003, issue of EOS Transactions of the American Geophysical Union. These two false-color MISR images were acquired before and after the event, on January 15 and 31, respectively. The earthquake epicenter was located about 80 kilometers east of the city of Bhuj, situated in the lower part of the images. The later image depicts numerous areas where groundwater flowed up to the surface, including within the Rann of Kutch, as well as near the Indo-Pakistani border. These regions of earthquake-associated surface water are apparent up to 200 kilometers from the earthquake's epicenter. Water was observed in many remote areas, especially near the Indo-Pakistani border, which were not easily accessible to survey teams on the ground. Changes in reflection at different view angles and in the near-infrared spectral region assist with the identification of surface water, which appears here in shades of blue and purple. In these visualizations, data from the red band of MISR's most obliquely backward and forward-viewing cameras are displayed as red and blue, respectively, and data from the near-infrared band of MISR's vertically-downward viewing (nadir) camera are displayed as green. Water bodies tend to be more absorbing in the near-infrared, and to be brighter in the view acquired by the more sun-facing (in this case, the 70-degree forward) camera. This combination enhances the ability to distinguish wet surfaces. True color and multi-angle visualizations [ http://earthobservatory.nasa.gov/Newsroom/NewImages/images.php3?img_id=4810 ] of these data were also released in April 2001. The Multi-angle Imaging SpectroRadiometer observes the daylit Earth continuously and every 9 days views the entire globe between 82 degrees north and 82 degrees south latitude. The |
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Dewatering Effects from the
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| Title |
Dewatering Effects from the Gujarat Earthquake |
| Description |
MISR Browse Image Viewer [ http://earthobservatory.nasa.gov/cgi-bin/redirect?http://eosweb.larc.nasa.gov/MISRBR/ ] provides access to low-resolution true-color versions of these images. This data product was generated from a portion of the imagery acquired during Terra orbits 5736 and 5969. The full-size images cover an area of 215 kilometers x 156 kilometers, and utilize data from blocks 71 to 72 within World Reference System-2 path 151. Image courtesy NASA/GSFC/LaRC/JPL, MISR Team. [ http://earthobservatory.nasa.gov/cgi-bin/redirect?http://www-misr.jpl.nasa.gov/ ] Text by Clare Averill (Acro Service Corporation/JPL) and David J. Diner (JPL)., browse image of orbit 5969 (380 KB JPEG) On January 26, 2001, when India's Republic Day is normally celebrated, a devastating earthquake hit the state of Gujarat. About 20,000 people died and millions were injured throughout the region. The earthquake had a magnitude of 7.7 on the Richter scale. After the earthquake, local residents reported a mixture of water and sediments fountaining from the Earth. These effects, referred to as dewatering, can result from intense ground shaking by strong earthquakes in regions with shallow water tables. Scientists initially observed dewatering in parts of the Rann of Kutch (a large salt pan in northern Gujarat), and in areas close to the earthquake epicenter. Recent research utilizes the unique capabilities of the Multi-angle Imaging SpectroRadiometer (MISR) instrument to observe earthquake-related dewatering over a broader area (related story: NASA Satellite Helps Scientists See Effects of Earthquakes in Remote Areas [ http://earthobservatory.nasa.gov/Newsroom/NasaNews/2003/2003020511146.html ]). This research is published in the February 4, 2003, issue of EOS Transactions of the American Geophysical Union. These two false-color MISR images were acquired before and after the event, on January 15 and 31, respectively. The earthquake epicenter was located about 80 kilometers east of the city of Bhuj, situated in the lower part of the images. The later image depicts numerous areas where groundwater flowed up to the surface, including within the Rann of Kutch, as well as near the Indo-Pakistani border. These regions of earthquake-associated surface water are apparent up to 200 kilometers from the earthquake's epicenter. Water was observed in many remote areas, especially near the Indo-Pakistani border, which were not easily accessible to survey teams on the ground. Changes in reflection at different view angles and in the near-infrared spectral region assist with the identification of surface water, which appears here in shades of blue and purple. In these visualizations, data from the red band of MISR's most obliquely backward and forward-viewing cameras are displayed as red and blue, respectively, and data from the near-infrared band of MISR's vertically-downward viewing (nadir) camera are displayed as green. Water bodies tend to be more absorbing in the near-infrared, and to be brighter in the view acquired by the more sun-facing (in this case, the 70-degree forward) camera. This combination enhances the ability to distinguish wet surfaces. True color and multi-angle visualizations [ http://earthobservatory.nasa.gov/Newsroom/NewImages/images.php3?img_id=4810 ] of these data were also released in April 2001. The Multi-angle Imaging SpectroRadiometer observes the daylit Earth continuously and every 9 days views the entire globe between 82 degrees north and 82 degrees south latitude. The |
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Eruption of Klyuchevskaya Vo
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Eruption of Klyuchevskaya Volcano |
| Description |
The rising sun bathes the eastern half of Russia's Kamchatka Peninsula with light, casting long shadows in the west. The shadows highlight the plume of ash that continues to rise from the Klyuchevskaya Volcano. The largest and most active volcano on the peninsula, Klyuchevskaya has erupted regularly since its first recorded eruption in 1697. Its most recent activity began in mid-January 2005, and has not abated. Dark ash from the ongoing eruption dusts the snow in this image, acquired by the Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER [ http://asterweb.jpl.nasa.gov/ ]) on NASA's Terra [ http://terra.nasa.gov/ ] satellite on March 12, 2005. In addition to the large plume of ash visible in this image, the ongoing eruption has sent molten lava down the volcano's northeast slope, where it is melting the Ehrman glacier. This activity may be responsible for the rivers of water that can be seen in the snow near the northeast base of the volcano. NASA image created by Jesse Allen, Earth Observatory, using data provided courtesy of NASA/GSFC/MITI/ERSDAC/JAROS, and U.S./Japan ASTER Science Team. |
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Rice Cultivation in Northwes
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Rice Cultivation in Northwest Italy |
| Description |
The lowlands of Lombardy and Piedmont in northwest Italy are some of the most highly developed irrigation areas in the world. Irrigated lands cover at least 160,000 acres in this part of Italy, where rice is the most important crop. These views of the region were acquired on May 8, 2005, by NASA's Multi-angle Imaging SpectroRadiometer (MISR). The multiple viewing angles provided by MISR's nine cameras make it possible to tell wet surfaces, including flooded lands, from other surfaces, and they also make cities easy to locate. The left-hand image is a natural-color view acquired by MISR's downward-looking (nadir) camera, and the right-hand image is a combination of red band data from MISR's 60-degree-backward-, nadir, and 60-degree-forward-viewing cameras. (Red band is what scientists call the "channel" on the sensor that detects red light.) Color changes indicate surface texture, which is influenced by terrain, vegetation structure, soil type, and surface wetness. Wet surfaces or areas with standing water appear in blue or purple-blue hues. The purple-blue areas that dominate the center-left part of the image are part of the extensive irrigation network that exists throughout the plains and meadows of the region. Cities with tall buildings appear in red-orange hues. In this type of image, the city of Milan is the most obvious. The small orange area in the center of the purple inundated area indicates the location of Vercelli, and the larger city of Milan is the orange area to the northeast, on the other side of the Ticino River. To a lesser extent, the cities of Novara, Pavia, Galliate, Mortara, and Vigevano are also identifiable by their orange hues. MISR can tell various surface features like cities or irrigated areas apart because of the way surfaces reflect light. A smooth water surface tends to reflect sunlight away from the Sun. This effect is most apparent when a satellite views the surface with the Sun in front of the camera. Similarly, rough surfaces tend to reflect light back towards the Sun, and this "backward scattering" is most obvious when a satellites views a surface with the Sun behind the camera. Clouds present over the high country to the west of the Lago Maggiore (upper left corner) and along the coast of the Golfo di Genova (bottom) appear in a different spot for each view angle, creating a rainbow-like appearance. Mountains also have a "wavy" look in the multi-angle combination because, like clouds, their height above the surface makes them appear in a different spot in each camera's view angle. The Multi-angle Imaging SpectroRadiometer observes the daylit Earth continuously, viewing the entire globe between 82 degrees North and 82 degrees South latitude every nine days. This image covers an area of about 131 kilometers by 191 kilometers. These data products were generated from a portion of the imagery acquired during Terra orbit 28660 and utilize data from block 54 within World Reference System-2 path 193. MISR was, built and is managed by NASA's Jet Propulsion Laboratory, Pasadena, CA, for NASA's Science Mission Directorate, Washington, DC. The Terra satellite is managed by NASA's Goddard Space Flight Center, Greenbelt, MD. JPL is managed for NASA by the California Institute of Technology. Image courtesy NASA/GSFC/LaRC/JPL, MISR Team. [ http://www-misr.jpl.nasa.gov/ ] Text by Clare Averill (Raytheon ITSS/JPL) |
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Natural Saturn On The Cassin
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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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Southwest Mercury
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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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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. |
|
Stereo Eros
| Title |
Stereo Eros |
| Explanation |
Get out your red/blue glasses [ http://mpfwww.jpl.nasa.gov/MPF/mpf/glasses.html ] and float next to asteroid 433 Eros [ http://www.boulder.swri.edu/~cchapman/finderos.html ], 260 million kilometers away! Orbiting the Sun once every 1.8 earth-years, asteroid Eros [ http://near.jhuapl.edu/eros/history/eros_useful.html ] is a diminutive 40 x 14 x 14 kilometer world of undulating horizons, craters, boulders [ http://antwrp.gsfc.nasa.gov/apod/ap000216.html ] and valleys. Its unsettling scale and bizarre shape are emphasized in this picture [ http://near.jhuapl.edu/NEAR/iod/20000218/index.html ] - a mosaic of recent images from the NEAR spacecraft processed [ http://visearth.ucsd.edu/Stereo/ ] to yield a stereo anaglyphic [ http://near.jhuapl.edu/NEAR/3_d.html ] view. Along with dramatic chiaroscuro, NEAR's 3-D imaging provides important measurements of the asteroid's landforms and structures, and hopefully clues to the origin [ http://near.jhuapl.edu/NEAR/Voyage/1.html ] of this city-sized chunk of solar system [ http://space.jpl.nasa.gov/ ]. The smallest features visible here are about 30 meters across. |
|
Saturn At Night
| Title |
Saturn At Night |
| Explanation |
From a spectacular [ http://antwrp.gsfc.nasa.gov/apod/ap970829.html ] vantage point over 1.4 billion [ http://antwrp.gsfc.nasa.gov/apod/ap980620.html ] kilometers from the sun, the Voyager [ http://nssdc.gsfc.nasa.gov/planetary/voyager.html ] 1 spacecraft looked back toward the inner solar system to record this startling view [ http://photojournal.jpl.nasa.gov/cgi-bin/ PIAGenCatalogPage.pl?PIA00335 ] of Saturn's nightside. The picture was taken on November 16, 1980, some four days after the robot spacecraft's closest approach to the gorgeous gas giant [ http://seds.lpl.arizona.edu/nineplanets/nineplanets/saturn.html ]. The crescent planet casts a broad shadow [ http://antwrp.gsfc.nasa.gov/apod/ap000212.html ] across its bright rings while the translucent rings themselves can be seen to cast a shadow on Saturn's cloud tops [ http://antwrp.gsfc.nasa.gov/apod/ap951018.html ]. Since Earth is closer to the sun than Saturn [ http://nssdc.gsfc.nasa.gov/photo_gallery/photogallery-saturn.html ], only Saturn's dayside is visible to Earth-bound telescopes [ http://www.seds.org/billa/bigeyes.html ] which could never take a picture like this one. After this successful [ http://vraptor.jpl.nasa.gov/voyager/vgrsat_fs.html ] flyby two decades ago, Voyager 1 has continued outward bound [ http://vraptor.jpl.nasa.gov/flteam/weekly-rpts/current.html ] and is presently humanity's most distant spacecraft [ http://vraptor.jpl.nasa.gov/voyager/ vimdesc.html ]. The next spacecraft to approach Saturn will be Cassini [ http://www.jpl.nasa.gov/cassini/ ], on course to arrive in 2004. |
|
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. |
|
Saturn-Sized Worlds Discover
…
| Title |
Saturn-Sized Worlds Discovered |
| Explanation |
The last decade [ http://antwrp.gsfc.nasa.gov/apod/ap991229.html ] saw the profound discovery of many worlds [ http://origins.stsci.edu/news/2000/01/background.html ] beyond our solar system, but none analogs of our home planet Earth [ http://earthobservatory.nasa.gov/ ]. Exploiting precise observational techniques, astronomers inferred [ http://cannon.sfsu.edu/~gmarcy/planetsearch/planetsearch.html ] the presence of well over two dozen extrasolar planets [ http://cfa-www.harvard.edu/planets/ ], most nearly as massive as gas giant Jupiter or more, in close orbits around sun-like stars. Less massive planets must certainly exist, and yesterday preeminent planet-finders announced [ http://origins.stsci.edu/news/2000/01/ index.html ] the further detection of two more new worlds -- each a potentially smaller, saturn-sized planet. The parent [ http://antwrp.gsfc.nasa.gov/apod/ap990611.html ] suns are 79 Ceti (constellation Cetus [ http://www.astro.wisc.edu/~dolan/constellations/ constellations/Cetus.html ]), at a distance of 117 light-years, and HD46375 (constellation Monoceros [ http://www.astro.wisc.edu/~dolan/ constellations/constellations/Monoceros.html ]), 109 light-years away. With at least 70 percent the mass of Saturn, 79 Ceti's planet orbits [ http://origins.stsci.edu/news/2000/01/animations.html ] on average 32.5 million miles from the star compared to 93 million miles for the Earth-Sun distance [ http://antwrp.gsfc.nasa.gov/apod/ap981212.html ]. This arresting artist's vision depicts the newly discovered world with rings and moons, known characteristics of giant planets in our solar system. HD46375's planet is at least 80 percent Saturn's mass, orbiting only 3.8 million miles from its parent star. While Saturn's [ http://nssdc.gsfc.nasa.gov/planetary/ factsheet/saturnfact.html ] mass is only one third of Jupiter's [ http://nssdc.gsfc.nasa.gov/planetary/ factsheet/jupiterfact.html ], it is still about 100 times that of Earth, and dramatic discoveries in the search [ http://tpf.jpl.nasa.gov/ ] for smaller planets are still to come [ http://sim.jpl.nasa.gov/science/ planet.html ]. |
|
Exploring Comet Tails
| Title |
Exploring Comet Tails |
| Explanation |
Comets [ http://seds.lpl.arizona.edu/billa/tnp/comets.html ] are known for their tails. In the spring [ http://antwrp.gsfc.nasa.gov/apod/ap970320.html ] of 1997 and 1996 Comet Hale-Bopp [ http://encke.jpl.nasa.gov/hale_bopp_info.html ] (above) and Comet Hyakutake [ http://encke.jpl.nasa.gov/comets_long/96B2.html ] gave us stunning examples [ http://pages.prodigy.net/pam.orman/JoeGallery.html ] as they passed near the Sun. These extremely active comets [ http://antwrp.gsfc.nasa.gov/apod/ap980410.html ] were bright, naked-eye spectacles offering researchers an opportunity to telescopically [ http://encke.jpl.nasa.gov/ ] explore the composition of primordial chunks of our solar system by studying their long and beautiful tails. But it has only recently been discovered that surprising readings [ ftp://ftp.hq.nasa.gov/pub/pao/pressrel/2000/00-055.txt ] from experiments on-board the interplanetary Ulysses probe [ http://ulysses.jpl.nasa.gov ] which lasted for several hours on May 1, 1996, indicate the probe passed through [ http://www.sp.ph.ic.ac.uk/Ulysses/comet/ ] comet Hyakutake's tail! Ulysses experiments were intended [ http://ulysses.jpl.nasa.gov/science/objectives.html ] to study the Sun and solar wind and the spacecraft-comet [ http://stardust.jpl.nasa.gov/ ] encounter was totally unanticipated. Relative positions of Ulysses [ http://ulysses-ops.jpl.esa.int/ulysses/ ] and Hyakutake on that date indicate that this comet's ion tail [ http://antwrp.gsfc.nasa.gov/apod/ap960319.html ] stretched an impressive 360 million miles or about four times the Earth-Sun distance [ http://antwrp.gsfc.nasa.gov/apod/ap981212.html ]. This makes Hyakutake's tail the longest ever recorded [ http://heasarc.gsfc.nasa.gov/docs/heasarc/missions/isee3.html ] and suggests that comet tails [ http://antwrp.gsfc.nasa.gov/apod/ap960327.html ] are much longer than previously believed. |
|
Pleiades, Planets, And Hot P
…
| Title |
Pleiades, Planets, And Hot Plasma |
| Explanation |
Bright stars of the Pleiades, four planets, and erupting solar plasma are all captured in this spectacular image [ http://sohowww.nascom.nasa.gov/hotshots/ ] from the space-based SOlar and Heliospheric Observatory (SOHO). In the foreground of the 15 degree wide field of view, a bubble of hot plasma, called a Coronal Mass Ejection (CME [ http://antwrp.gsfc.nasa.gov/apod/ap000309.html ]), is blasting away from the active Sun [ http://www.spaceweather.com/ ] whose position and relative size is indicated by the central white circle. Beyond [ http://sohowww.nascom.nasa.gov/hotshots/2000_05_03/ diagram1.jpg ] appear four of the five [ http://antwrp.gsfc.nasa.gov/apod/ap000505.html ] naked-eye planets [ http://sse.jpl.nasa.gov/features/planets/ planetsfeat.html ] -- courtesy [ http://www.badastronomy.com/bad/misc/planets.html ] of the planetary alignment [ http://science.nasa.gov/headlines/y2000/ ast30mar_1m.htm#alignments ] which did not destroy the world! In the background are distant stars and the famous Pleiades [ http://www.seds.org/messier/m/m045.html ] star cluster, also easily visible to the unaided eye when it shines in the night sky [ http://antwrp.gsfc.nasa.gov/apod/ap000504.html ]. Distances for these familiar [ http://www.seds.org/nineplanets/nineplanets/ nineplanets.html ] celestial objects are, the Sun [ http://helios.gsfc.nasa.gov/sun.html ], 150 million kilometers away, Mercury, Venus, Jupiter, and Saturn, about 58, 110, 780, and 1,400 million kilometers beyond the Sun respectively, and the Pleiades [ http://www.ras.ucalgary.ca/~gibson/pleiades/ ] star cluster at a mere 3,800 trillion kilometers (400 light-years). SOHO itself orbits 1.5 million kilometers sunward of planet Earth. The image [ http://sohowww.nascom.nasa.gov/data/latestimages.html ] was recorded by the Large Angle and Spectrometric COronagraph (LASCO) instrument on board SOHO on Monday, May 15 at 10:42 UT. |
|
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 |
|
Dog-Bone Shaped Asteroid 216
…
| Title |
Dog-Bone Shaped Asteroid 216 Kleopatra |
| Explanation |
An asteroid [ http://www.seds.org/nineplanets/nineplanets/asteroids.html ] the size of New Jersey [ http://www.state.nj.us/ ] that orbits the Sun [ http://antwrp.gsfc.nasa.gov/apod/sun.html ] between Mars [ http://www.solarviews.com/eng/mars.htm ] and Jupiter [ http://www.jpl.nasa.gov/galileo/jupiter/jupiter.html ] has been discovered to have an unusual dog-bone shape. Asteroid 216 Kleopatra [ http://echo.jpl.nasa.gov/~ostro/kle/index.html ], recently mapped with Earth-based radar [ http://www-paoc.mit.edu/Radar_Lab/FAQ.html ], reflects radio waves [ http://imagers.gsfc.nasa.gov/ems/radio.html ] so well that astronomers speculate [ http://echo.jpl.nasa.gov/~ostro/kle/jpl_press_release ] it is composed mostly of metals such as nickel [ http://pearl1.lanl.gov/periodic/elements/28.html ] and iron [ http://www.webelements.com/webelements/scholar/elements/iron/key.html ]. The unusual shape and composition of 216 Kleopatra [ http://sc6.sc.eso.org/~fmarchis/Science/Kleopatra/ ] may derive from the central regions of a tremendous collision between larger asteroids [ http://antwrp.gsfc.nasa.gov/apod/asteroids.html ] billions of years ago. Kleopatra [ http://www.space.com/scienceastronomy/solarsystem/dogbone_asteroid_000505.html ] is not completely solid - its surface is loosely consolidated rubble, although its core may contain large solid-metal lodes. Kleopatra [ http://www.spaceref.com/news/viewnews.html?id=131 ] will never strike the Earth [ http://antwrp.gsfc.nasa.gov/apod/ap980313.html ], but it may one day serve as a valuable source of raw building materials. |
|
Saturn at Night
| Title |
Saturn at Night |
| Explanation |
This is what Saturn looks like at night. In contrast to the human-made lights [ http://antwrp.gsfc.nasa.gov/apod/ap040822.html ] that cause the nighttime side of Earth to glow faintly, Saturn's faint nighttime glow is primarily caused by sunlight reflecting off of its own majestic rings [ http://antwrp.gsfc.nasa.gov/apod/ap050525.html ]. The above image [ http://photojournal.jpl.nasa.gov/catalog/PIA08252 ] of Saturn at night was captured in July by the Cassini spacecraft [ http://saturn.jpl.nasa.gov/spacecraft/index.cfm ] now orbiting Saturn. The above image [ http://photojournal.jpl.nasa.gov/catalog/PIA08252 ] was taken when the Sun was far in front of the spacecraft. From this vantage point, the northern hemisphere of nighttime Saturn, visible on the left, appears eerily dark. Sunlit rings are visible ahead, but are abruptly cut off by Saturn [ http://en.wikipedia.org/wiki/Saturn ]'s shadow. In Saturn's southern hemisphere, visible on the right, the dim reflected glow from the sunlit rings is most apparent. Imprinted on this diffuse glow, though, are thin black stripes not discernable to any Earth telescope [ http://antwrp.gsfc.nasa.gov/apod/ap971227.html ] -- the silhouetted C ring [ http://en.wikipedia.org/wiki/Saturn%27s_rings ] of Saturn. Cassini has been orbiting Saturn since 2004 and its mission [ http://en.wikipedia.org/wiki/Cassini-Huygens ] is scheduled to continue until 2008. |
|
Sunlight Through Saturn's Ri
…
| Title |
Sunlight Through Saturn's Rings |
| Explanation |
Normally, earth-bound [ http://space.jpl.nasa.gov/ ] astronomers view Saturn's spectacular ring system [ http://antwrp.gsfc.nasa.gov/apod/ap990130.html ] fully illuminated by reflected sunlight. However, this intriguing picture [ http://hubble.stsci.edu/news_.and._views/pr.cgi?1996+18 ] was made to take advantage of an unusual orientation [ http://www.jpl.nasa.gov/saturn/ ], with the Sun actually illuminating the rings from below. The three bright ring features [ http://ringmaster.arc.nasa.gov/saturn/saturn.html ] are visible because the rings themselves are not solid. Composed of many separate chunks of rocky, icy material, the rings allow the scattered sunlight to pass through them -- offering [ http://www.jpl.nasa.gov/cassini/educatorguide/ ] a dramatic demonstration that they are "not" continuous, uninterrupted bands of material. The picture is [ http://oposite.stsci.edu/pubinfo/gif/SatRPC11.txt ] a false-color composite based on Hubble Space Telescope images recorded in November of 1995. |
|
Comet LINEAR Approaches
| Title |
Comet LINEAR Approaches |
| Explanation |
Just possibly, a new comet [ http://www.seds.org/nineplanets/nineplanets/comets.html ] may become bright enough to see without binoculars later this month. Comet C/1999 S4 LINEAR [ http://www.skypub.com/sights/comets/0007linearS4.html ] is rapidly approaching both the Earth [ http://antwrp.gsfc.nasa.gov/apod/earth.html ] and the Sun [ http://antwrp.gsfc.nasa.gov/apod/ap000522.html ] from the outer Solar System [ http://www.exploratorium.edu/ronh/solar_system/ ], and should be at its brightest around 2000 July 25 in the early evening sky of northern observers. The comet was discovered [ http://www.swisr.org/newcomet.html ] by chance by project LINEAR [ http://www.ll.mit.edu/LINEAR/ ] last September. The above time-lapse sequence [ http://www.astrophotographer.com/C1999-S4_1Jul2000.html ] of Comet LINEAR [ http://encke.jpl.nasa.gov/whats_visible.html#1999S4 ] was taken on 2000 July 2 from Arizona [ http://www.state.az.us/ ] and shows the comet's movement over only 19 minutes. Although Comet LINEAR [ http://cfa-www.harvard.edu/iau/Ephemerides/Comets/1999S4.html ]'s positions will be known quite accurately, the comet's future brightness and tail [ http://antwrp.gsfc.nasa.gov/apod/ap000413.html ] length can only be guessed, and it is quite possible that neither will become very impressive. |
|
Tails Of Comet LINEAR
| Title |
Tails Of Comet LINEAR |
| Explanation |
Comet C/1999 S4 LINEAR is only one of many [ http://www.ll.mit.edu/LINEAR/neos.html ] comets discovered with the Lincoln Near Earth Asteroid Research [ http://www.ll.mit.edu/LINEAR/ ] (LINEAR) telescope operating near Soccoro, New Mexico, USA. Traveling steadily southward through Earth's night sky, C/1999 S4 passed perihelion (closest approach to the Sun) yesterday on what is likely its first trip [ http://www.skypub.com/sights/comets/0007linearS4.html ] through the inner solar system. Now fading, comet LINEAR [ http://www.swisr.org/newcomet.html#Anchor Latest ] became no brighter than about 6th magnitude, but is still easily visible with binoculars in northern hemisphere skies. While the memorable comets Hale-Bopp [ http://antwrp.gsfc.nasa.gov/apod/ap970320.html ] and Hyakutake [ http://antwrp.gsfc.nasa.gov/apod/ap980717.html ] were much brighter, comet LINEAR [ http://antwrp.gsfc.nasa.gov/apod/ap000704.html ] is displaying [ http://cfa-www.harvard.edu/iauc/07400/07461.html#Item2 ] delightful tails evident in this false-color composite image from [ http://www.fiz.uni-lj.si/astro/comets/images/99s4.html ] the Crni Vrh Observatory [ http://www.fiz.uni-lj.si/astro/comets/cvobs.html ] in Slovenia. The combined series of exposures made on July 22nd are registered on the comet. In the resulting picture, stars appear as rows of dots, but the faint structures in the comet's tail are beautifully recorded. Presently seen moving from Ursa Major to Leo [ http://www.astro.wisc.edu/~dolan/constellations/ constellations.html ] this comet LINEAR [ http://encke.jpl.nasa.gov/whats_visible.html#1999S4 ] will begin to shine in southern hemisphere skies in August. |
|
Other Worlds and HD 38529
| Title |
Other Worlds and HD 38529 |
| Explanation |
After the latest round of discovery announcements [ http://www.iau.org/ga24press/ ], the list of known worlds of distant suns [ http://www.spaceart.org/lcook/extrasol.html ] has grown to 50 [ http://www.spaceref.com/news/viewnews.html?id=200 ]. While extrasolar planet [ http://exoplanets.org/ ] discoveries are [ http://obswww.unige.ch/~udry/planet/planet.html ] sure to continue, none - so far [ http://sim.jpl.nasa.gov/ ] - points clearly to another planetary system like our own [ http://antwrp.gsfc.nasa.gov/apod/ap991229.html ]. Take, for example, the newly discovered parent [ http://antwrp.gsfc.nasa.gov/apod/ap990611.html ] star HD38529 [ http://www.obspm.fr/encycl/HD38529.html ]. Shining in Earth's night sky at 6th magnitude, this sun-like star lies 137 light-years away in the constellation Orion [ http://aibn47.astro.uni-bonn.de/~gallery/constellations/orion/ main.html ]. Like most of the known extrasolar planets [ http://www.obspm.fr/encycl/encycl.html ], HD38529's planet was discovered by detecting the telltale Doppler wobble [ http://exoplanets.org/doppler.html ] in the parent star's spectrum. The data reveal that this planet orbits once every 14.3 days at an average of only 0.13 times the Earth-Sun distance and has a minimum of 0.77 Jupiter masses (about 240 Earth masses). There is even evidence [ http://www.iau.org/ga24press/pr000807_3.html#1 ] in the wobble data that HD38529, and other stars with one known planet have additional massive planets orbiting them. In this dramatic artist's vision, HD38529 and its newfound world are viewed from the moon of another massive ringed planet [ http://antwrp.gsfc.nasa.gov/apod/ap000330.html ] orbiting farther out. The ringed planet's moon is imagined to have a thin atmosphere and a surface covered with icy sheets and ridges similar to those found on Jupiter's moon Europa [ http://galileo.jpl.nasa.gov/moons/europa.html ]. |
|
NGC1850: Star Cluster in the
…
| Title |
NGC1850: Star Cluster in the LMC |
| Explanation |
NGC1850 is a large cluster of stars located a mere 166,000 light-years from Earth in our neighboring galaxy the Large Magellanic Cloud [ http://antwrp.gsfc.nasa.gov/apod/ap000222.html ] (LMC). The colors [ http://aibn47.astro.uni-bonn.de/~gallery/articles/ color.html ] in this beautiful Hubble Space Telescope composite image [ http://oposite.stsci.edu/pubinfo/PR/94/40.html ] of the cluster reveal [ http://antwrp.gsfc.nasa.gov/apod/ap990312.html ] different populations of stars. Yellowish stars are the main cluster stars, sun-like main sequence hydrogen burners [ http://antwrp.gsfc.nasa.gov/htmltest/gifcity/msblues.html ] about 50 million years old. The white stars are massive, hotter, and younger, about 4 million years old. Radiating strongly in ultraviolet light, they represent a loose cluster [ http://www.seds.org/messier/cluster.html ] themselves, perhaps within 200 light-years of the main cluster. Massive stars [ http://antwrp.gsfc.nasa.gov/apod/ap960509.html ] which formed in the older main cluster have long since disappeared, ending their lives in spectacular supernova explosions [ http://antwrp.gsfc.nasa.gov/apod/ap970225.html ]. Did expanding debris from these supernovae trigger the formation [ http://antwrp.gsfc.nasa.gov/apod/ap000219.html ] of the nearby younger cluster? Probably so. In any event, a few million years from now a similar fate awaits the massive stars of the younger cluster - burning brightly but briefly before they explode sending new clouds of stellar debris [ http://antwrp.gsfc.nasa.gov/apod/ap990725.html ] into space. |
|
STS-115: Stereo Portrait
| Title |
STS-115: Stereo Portrait |
| Explanation |
On September 12, astronaut Heidemarie Stefanyshyn-Piper snapped photos of her colleague Joseph Tanner during the STS-115 mission [ http://www.nasa.gov/mission_pages/shuttle/behindscenes/ 115_mission_overview.html ]. At the time, the spacesuited pair were working outside the shuttle orbiter Atlantis, some 300 kilometers above planet Earth [ http://antwrp.gsfc.nasa.gov/apod/ap060921.html ]. Portions of two of the pictures (S115-E-05750 [ http://spaceflight.nasa.gov/gallery/images/shuttle/ sts-115/html/s115e05750.html ] and S115-E-05753 [ http://spaceflight.nasa.gov/gallery/images/shuttle/ sts-115/html/s115e05753.html ]) have been combined in this spectacular 3D image - a stereo anaglyph intended to be viewed with red/blue glasses [ http://photojournal.jpl.nasa.gov/Help/VendorList.html ]. Included in the scene reflected in [ http://mirrorproject.com/ ] Tanner's visor is Stefanyshyn-Piper herself and the Sun shining above the Earth's distant horizon [ http://antwrp.gsfc.nasa.gov/apod/ap060719.html ]. |
|
Comet SWAN Brightens
| Title |
Comet SWAN Brightens |
| Explanation |
A newly discovered comet has brightened enough to be visible this week with binoculars. The picturesque comet [ http://antwrp.gsfc.nasa.gov/apod/ap050904.html ] is already becoming a favored target for northern sky imagers. Pictured above [ http://www.astrostudio.at/Astrofotos/astrofotos.php?k_id=69 ] just last week, Comet SWAN showed a bright blue-green coma and an impressive tail. Comet C/2006 M4 (SWAN) [ http://cometography.com/lcomets/2006m4.html ] was discovered in June in public images from the Solar Wind Anisotropies [ http://www.fmi.fi/research_space/space_7.html ] (SWAN) instrument of NASA and ESA [ http://en.wikipedia.org/wiki/ESA ]'s Sun-orbiting SOHO [ http://sohowww.nascom.nasa.gov/ ] spacecraft. Comet [ http://en.wikipedia.org/wiki/Comet ] SWAN, near magnitude six, will be visible with binoculars in the northeastern sky not far from the Big Dipper over the next few days before dawn. The comet [ http://www.aerith.net/comet/catalog/2006M4/2006M4.html ] is expected to reach its peak brightness this week. Passing its closest to the Sun two days ago, Comet SWAN [ http://ssd.jpl.nasa.gov/sbdb.cgi?ID=dK06M040;orb=1;cov=0#orb ] and will be at its closest to the Earth toward the end of this month. Comet SWAN's unusual orbit [ http://cfa-www.harvard.edu/cfa/ps/mpec/K06/K06S89.html ] appears to be hyperbolic [ http://adsabs.harvard.edu/abs/1992A&A...259..692K ], meaning that it will likely go off into interstellar space [ http://antwrp.gsfc.nasa.gov/apod/ap020210.html ], never to return. |
|
Earth from Saturn
| Title |
Earth from Saturn |
| Explanation |
What's that pale blue dot in this image taken from Saturn? Earth [ http://antwrp.gsfc.nasa.gov/apod/ap010204.html ]. The robotic Cassini spacecraft [ http://saturn.jpl.nasa.gov/spacecraft/index.cfm ] looked back toward its old home world earlier this month as it orbited Saturn [ http://en.wikipedia.org/wiki/Saturn_(planet) ]. Using Saturn itself to block the bright Sun [ http://antwrp.gsfc.nasa.gov/apod/ap030530.html ], Cassini imaged a faint dot on the right of the above photograph [ http://photojournal.jpl.nasa.gov/catalog/PIA08324 ]. That dot is expanded on the image inset, where a slight elongation in the direction of Earth's Moon [ http://antwrp.gsfc.nasa.gov/apod/ap030526.html ] is visible [ http://antwrp.gsfc.nasa.gov/apod/ap980904.html ]. Vast water oceans make Earth's reflection of sunlight somewhat blue [ http://www.sciam.com/askexpert_question.cfm?articleID=000CCDD2-DD07-1C71-9EB7809EC588F2D7 ]. Earth is home to over six billion humans [ http://desip.igc.org/populationmaps.html ] and over one octillion [ http://en.wikipedia.org/wiki/Octillion ] Prochlorococcus [ http://sciam.com/article.cfm?chanID=sa022&articleID=0005BE47-0078-1FA8-807883414B7F0000 ]. |
|
Eros At Sunset
| Title |
Eros At Sunset |
| Explanation |
Gleaming in the rays of the setting sun, boulders litter the rugged surface of asteroid 433 Eros [ http://near.jhuapl.edu/eros/ ]. The brightest boulder, at the edge of the large, shadowy crater near this picture's bottom center, is about 30 meters (100 feet) across. In orbit around Eros since February 2000, the NEAR Shoemaker [ http://near.jhuapl.edu/NEAR/ ] spacecraft's camera recorded the dramatic view [ http://near.jhuapl.edu/NEAR/iod/20000821/index.html ] earlier this month from an altitude of about 50 kilometers. Eros itself orbits [ http://www.fwkc.com/encyclopedia/low/articles/o/ o018000416f.html ] the Sun with a perihelion [ http://imagine.gsfc.nasa.gov/docs/ dictionary.html#perihelion ] of 1.13 Astronomical Units [ http://imagine.gsfc.nasa.gov/docs/ask_astro/ answers/980122b.html ] (AU) and aphelion [ http://imagine.gsfc.nasa.gov/docs/ dictionary.html#aphelion ] of 1.78 AU. Part of a class of near-Earth asteroids [ http://neo.jpl.nasa.gov/neo.html ], it spends much of its time between the orbits of Mars (at 1.5 AU) and Earth (at 1 AU) ... but it wasn't always that way. Eros and other near-Earth asteroids [ http://neo.planetary.org/ABCsOfNEOs/index.html ] originally orbited in the main asteroid belt [ http://seds.lpl.arizona.edu/nineplanets/nineplanets/ asteroids.html ], between Jupiter [ http://galileo.jpl.nasa.gov/jupiter/jupiter.html ] and Mars [ http://nssdc.gsfc.nasa.gov/planetary/factsheet/ marsfact.html ]. Over time, the gravitational influence of Jupiter and other planets perturbed their orbits sending them on trajectories closer [ http://antwrp.gsfc.nasa.gov/apod/ap000226.html ] to Earth. |
|
In the Shadow of Saturn
| Title |
In the Shadow of Saturn |
| Explanation |
In the shadow of Saturn, unexpected wonders appear. The robotic Cassini spacecraft [ http://saturn.jpl.nasa.gov/spacecraft/index.cfm ] now orbiting Saturn [ http://antwrp.gsfc.nasa.gov/apod/saturn.html ] recently drifted in giant planet's shadow [ http://antwrp.gsfc.nasa.gov/apod/ap040926.html ] for about 12 hours and looked back toward the eclipsed Sun [ http://antwrp.gsfc.nasa.gov/apod/ap010408.html ]. Cassini saw a view unlike any other. First, the night side of Saturn [ http://antwrp.gsfc.nasa.gov/apod/ap060912.html ] is seen to be partly lit by light reflected from its own majestic ring system [ http://www.planetary.org/saturn/images_saturn_rings.html ]. Next, the rings themselves appear dark when silhouetted against Saturn, but quite bright when viewed away from Saturn and slightly scattering [ http://www.daviddarling.info/encyclopedia/F/forward_scattering.html ] sunlight, in the above exaggerated color image [ http://photojournal.jpl.nasa.gov/catalog/PIA08329 ]. Saturn's rings light up so much that new rings [ http://photojournal.jpl.nasa.gov/catalog/PIA08322 ] were discovered, although they are hard to see in the above image. Visible in spectacular detail, however, is Saturn's E ring [ http://www.planetary.org/explore/topics/saturn/rings.html ], the ring created by the newly discovered ice-fountains [ http://antwrp.gsfc.nasa.gov/apod/ap051205.html ] of the moon Enceladus [ http://antwrp.gsfc.nasa.gov/apod/ap050906.html ], and the outermost ring visible above. Far in the distance [ http://antwrp.gsfc.nasa.gov/apod/ap060927.html ], visible on the image left just above the bright main rings, is the almost ignorable pale blue dot [ http://en.wikipedia.org/wiki/Pale_Blue_Dot ] of Earth. |
|
3D Mercury Transit
| Title |
3D Mercury Transit |
| Explanation |
Mercury is now [ http://www.astronomy.com/ASY/CS/forums/314872/ ShowPost.aspx ] visible shortly before dawn, the brightest "star" just above the eastern horizon. But almost two weeks ago Mercury [ http://antwrp.gsfc.nasa.gov/apod/ap061114.html ] actually crossed the face of the Sun for the second time in the 21st century. Viewed with red/blue glasses [ http://photojournal.jpl.nasa.gov/Help/VendorList.html ], this stereo anaglyph combines space-based images of the Sun and innermost planet in a just-for-fun 3D [ http://www.sungazer.net/3dtransit.html ] presentation of the Mercury transit [ http://www.transitofvenus.org/mercury.htm ]. The solar disk image is from Hinode [ http://solarb.msfc.nasa.gov/index.html ]. (sounds like "hee-no-day", means sunrise). A sun-staring observatory, Hinode was launched from Uchinoura Space Center and viewed the transit [ http://solar-b.nao.ac.jp/news_e/20061109_e.shtml ] from Earth orbit. Superimposed on Mercury's dark silhouette is a detailed image [ http://antwrp.gsfc.nasa.gov/apod/ap011124.html ] of the planet's rugged surface based on data from the Mariner 10 [ http://nssdc.gsfc.nasa.gov/nmc/tmp/1973-085A.html ] probe that flew by Mercury in 1974 and 1975. |
|
September Sky
| Title |
September Sky |
| Explanation |
Star clusters, planets, and a red giant posed for this portrait of the night [ http://antwrp.gsfc.nasa.gov/apod/ap000708.html ] sky from rural Jasper County, Iowa, USA. Astrophotographer [ http://geocities.com/stanzman_2001/ ] Stan Richard recorded the four minute time exposure looking east around midnight on September 3rd at Ashton-Wildwood Park. To avoid star trails [ http://pages.prodigy.net/pam.orman/JoeTrails.html ], his camera was mounted on a barndoor-style [ http://casa.colorado.edu/~rachford/widefield/ barndoor.html ] tracker to compensate for the Earth's rotation [ http://antwrp.gsfc.nasa.gov/apod/ap000715.html ]. Can you identify his celestial subjects? (Click on the image for a labeled version.) The Pleiades [ http://www.pantheon.org/mythica/articles/p/ pleiades.html ] and Hyades [ http://www.pantheon.org/mythica/articles/h/hyades.html ], the closest open or galactic star clusters [ http://www.seds.org/messier/open.html ] to the Sun, should be recognizable to beginning stargazers [ http://starchild.gsfc.nasa.gov/ ]. Of course gas giant Jupiter [ http://galileo.jpl.nasa.gov/jupiter/jupiter.html ] rules as the brightest object in the picture and the largest planet in the Solar System, but second largest planet Saturn [ http://www.jpl.nasa.gov/cassini/Kids/stories/ ] is also visible nearby. For sheer size cool red giant star Aldebaran [ http://www.astro.uiuc.edu/~kaler/sow/aldebaran.html ] is more impressive though, spanning about forty times the diameter of the Sun. Sixty light-years away and yellowish in this picture, Aldebaran is known as Alpha Tauri, the brightest star in Taurus [ http://aibn47.astro.uni-bonn.de/~gallery/constellations/ taurus/ ], the Bull. |
|
The Equal Night
| Title |
The Equal Night |
| Explanation |
Yesterday the Sun crossed [ http://www-spof.gsfc.nasa.gov/stargaze/Sseason.htm ] the celestial equator heading south, marking the Equinox -- the first day of Autumn in the northern hemisphere and Spring in the south [ http://antwrp.gsfc.nasa.gov/apod/ap000826.html ]. Equinox means "equal night" and with the Sun on the celestial equator [ http://www.physics.csbsju.edu/astro/CS/CSintro.html ], Earthlings will experience 12 hours of daylight and 12 hours of darkness. For those in the northern hemisphere, the days [ http://www.nsta.org/programs/sst/aws/unit2.htm ] will continue to grow shorter with the Sun marching [ http://www.lalc.k12.ca.us/laep/smart/Sunrise/k3les1.html ] lower in the sky as winter approaches. A few weeks after the Autumnal Equinox of 1994, the Crew of the Shuttle Endeavor [ http://antwrp.gsfc.nasa.gov/apod/ap950807.html ] recorded this image [ http://images.jsc.nasa.gov/images/pao/STS68/20172510.htm ] of the Sun poised [ http://sohowww.nascom.nasa.gov/data/realtime-images.html ] above the Earth's limb. Glare illuminates Endeavor's vertical tail (pointing toward the Earth) along with radar equipment [ http://southport.jpl.nasa.gov/ ] in the payload bay. |
|
Eclipse Moon Trail
| Title |
Eclipse Moon Trail |
| Explanation |
Tonight, Friday the 13th, October's big, bright, beautiful full Moon [ http://antwrp.gsfc.nasa.gov/apod/ap000113.html ] will be in the sky, rising as the sun sets. A time exposure of this evening's full Moon would show a brilliant circular arc or Moon trail tracing its celestial path. In fact, this single [ http://pages.prodigy.net/pam.orman/joemoon/ MoonPlanets_000120_2.html ], four hour long exposure from the evening of January 20 shows a full Moon trailing through hazy skies above [ http://pages.prodigy.net/pam.orman/ JoeGallery.html ] Phoenix, Arizona, USA. Of course, the picture also shows something you won't see tonight -- a total lunar eclipse [ http://www.mreclipse.com/Special/LEprimer.html ]. A lunar eclipse is caused when the full moon enters Earth's shadow [ http://image.gsfc.nasa.gov/poetry/ask/q2806.html ] and as the eclipsed Moon's light grows steadily fainter, the Moon trail becomes narrow and dim. The total eclipse phase, when the Moon passes completely within Earth's shadow [ http://space.jpl.nasa.gov/cgi-bin/wspace?tbody=3&vbody=103& month=1&day=21¢ury=20&decade=0&year=0&hour=04&minute=0& rfov=30&fovmul=-1&bfov=30 ], occurs near the middle of this Moon trail arc [ http://antwrp.gsfc.nasa.gov/apod/ap000905.html ]. But even during totality, the Moon trail is visible and noticeably red. Normally illuminated by sunlight which falls directly on its surface, during a total lunar eclipse the Moon is still illuminated [ http://antwrp.gsfc.nasa.gov/apod/ap991108.html ] by sunlight filtered and refracted through Earth's atmosphere. The refracted light lends the eclipsed Moon [ http://www.mreclipse.com/ ] a dim and reddish appearance. |
|
The Ecliptic Plane
| Title |
The Ecliptic Plane |
| Explanation |
The Plane of the Ecliptic is well illustrated in this picture from the 1994 lunar prospecting Clementine spacecraft. Clementine's star tracker camera image reveals (from right to left) the Moon [ http://lunar.arc.nasa.gov/ ] lit by Earthshine, the Sun's corona [ http://antwrp.gsfc.nasa.gov/apod/ap960530.html ] rising over the Moon's dark limb, and the planets Saturn [ http://www.jpl.nasa.gov/cassini/ ], Mars [ http://mars.jpl.nasa.gov/ ], and Mercury [ http://sd-www.jhuapl.edu/MESSENGER/ ]. The ecliptic plane is defined as the imaginary plane containing the Earth's orbit around the Sun. In the course of a year, the Sun's apparent path [ http://www.astro.wisc.edu/~dolan/constellations/extra/Zodiac.html ] through the sky lies in this plane. The Solar System's [ http://space.jpl.nasa.gov/ ] planetary bodies all tend to lie near this plane, since they were formed from the Sun's spinning, flattened, proto-planetary disk [ http://antwrp.gsfc.nasa.gov/apod/ap990611.html ]. The snapshot above nicely captures a momentary line-up looking out along this fundamental plane of our Solar System [ http://antwrp.gsfc.nasa.gov/apod/ap990505.html ]. |
|
Martian Analemma
| Title |
Martian Analemma |
| Explanation |
On planet Earth, an analemma [ http://www.analemma.com ] is the figure-8 loop [ http://antwrp.gsfc.nasa.gov/apod/ap061223.html ] you get when you mark the position of the Sun at the same time each day throughout the year. But similarly marking the position of the Sun in the Martian sky would produce the simpler, stretched pear shape [ http://www.giss.nasa.gov/research/briefs/allison_02/ ] in this digital illustration, based on the Mars Pathfinder project's famous Presidential Panorama [ http://antwrp.gsfc.nasa.gov/apod/ap000514.html ] view from the surface. The simulation shows the late afternoon [ http://www.giss.nasa.gov/data/mars/time/ ] Sun that would have been seen from the Sagan Memorial Station [ http://mars.jpl.nasa.gov/MPF/index1.html ] once every 30 Martian days [ http://en.wikipedia.org/wiki/Timekeeping_on_Mars ] (sols) beginning on Pathfinder's Sol 24 (July 29, 1997). Slightly less bright, the simulated Sun is only about two thirds the size as seen from Earth, while the Martian [ http://pweb.jps.net/~tgangale/mars/faq.htm ] dust, responsible for the reddish sky of Mars, also scatters some blue light around the solar disk. |
|
Heaven on Earth
| Title |
Heaven on Earth |
| Explanation |
If sometimes it appears that the entire Milky Way Galaxy [ http://www.seds.org/messier/more/mw.html ] is raining down on your head, do not despair. It happens twice a day. As the Sun rises [ http://antwrp.gsfc.nasa.gov/apod/ap990817.html ] in the East, wonders of the night sky become less bright than the sunlight scattered [ http://antwrp.gsfc.nasa.gov/apod/ap991110.html ] by our own Earth's atmosphere [ http://www.sciencemadesimple.com/sky_blue.html ], and so fade from view. They will only rotate back into view when the Earth again eclipses our bright Sun at dusk [ http://antwrp.gsfc.nasa.gov/apod/ap980526.html ]. This battle between heaven and Earth was captured dramatically above [ http://www.ne.jp/asahi/stellar/scenes/milky_e/mw03.htm ] during the last few minutes of daylight on 1999 August 10 in Koumi [ http://www.yahoo.co.jp/Regional/Japanese_Regions/Shinetu/Nagano/Cities/Koumi/ ], Japan [ http://www.odci.gov/cia/publications/factbook/geos/ja.html ]. Dark dust [ http://antwrp.gsfc.nasa.gov/apod/ap990509.html ], millions of stars [ http://www.astro.wisc.edu/~dolan/constellations/extra/brightest.html ], and bright glowing red gas [ http://antwrp.gsfc.nasa.gov/apod/emission_nebulae.html ] highlight the plane [ http://antwrp.gsfc.nasa.gov/apod/ap990224.html ] of our Milky Way Galaxy [ http://antwrp.gsfc.nasa.gov/apod/ap971229.html ], which lies on average thousands of light years [ http://einstein.stcloudstate.edu/Dome/constellns/lightyear.html ] behind Earth [ http://antwrp.gsfc.nasa.gov/apod/ap990131.html ]'s yellow and green reflecting clouds [ http://www-airs.jpl.nasa.gov/html/edu/clouds/What_are_clouds.html ]. |
|
A Tail of Two Hemispheres
| Title |
A Tail of Two Hemispheres |
| Explanation |
By January 19/20 Comet McNaught's [ http://antwrp.gsfc.nasa.gov/apod/ap070122.html ] magnificent dust tail stretched for about 150 million kilometers (~1 AU), requiring images from both southern [ http://spaceweather.com/comets/ gallery_mcnaught_page14.php ] and northern [ http://spaceweather.com/comets/ gallery_mcnaught_page13.php ] hemispheres of planet Earth to take it all in. Two such views - from Cerro Paranal [ http://antwrp.gsfc.nasa.gov/apod/ap070123.html ] in Chile (left) and the Carnic Alps [ http://antwrp.gsfc.nasa.gov/apod/ap070124.html ] in Italy - are combined in this unique graphic [ http://www.ts.astro.it/McNaught.html ] that also outlines a perspective view of the comet's orbit (dotted line) and relative position of the Sun. Driven by [ http://www.ifa.hawaii.edu/faculty/jewitt/tail.html ] solar radiation pressure the dust tail initially points away from the Sun, but also trails outside the comet's orbit [ http://shadowandsubstance.com/ ]. Astronomers try to account [ http://www.lpi.usra.edu/books/CometsII/7006.pdf ] for the complex structure along the tail, including the pronounced striations, by considering [ http://adsabs.harvard.edu/cgi-bin/ bib_query?1980AJ.....85.1538S ] forces acting on the dust (e.g. gravity, solar wind [ http://www.phy6.org/Education/wsolwind.html ] and radiation) as well as the release time and size of the dust grains [ http://stardust.jpl.nasa.gov/home/index.html ]. In the diagram, the modeled location of dust grains released at approximately the same time relative to perihelion [ http://antwrp.gsfc.nasa.gov/apod/ap070119.html ] passage, "synchrones", are shown as dashed lines. The location of grains of similar size, "syndynes", are shown as solid lines. |
|
Solar Eclipse from the Moon
| Title |
Solar Eclipse from the Moon |
| Explanation |
Parts of Saturday's (March 3) lunar eclipse [ http://sunearth.gsfc.nasa.gov/eclipse/OH/OH2007.html ] will be widely visible. For example, skywatchers [ http://www.xs4all.nl/~carlkop/maaneclips2007/ leclips2007.html ] in Europe, Africa, and western Asia will be able to see the entire spectacle of the Moon gliding through Earth's shadow, but in eastern North America the Moon will rise already in its total eclipse phase [ http://www.mreclipse.com/Special/LEprimer.html ]. Of course if you traveled to the Moon's near side [ http://science.nasa.gov/headlines/y2007/ 12feb_lunareclipse.htm ], you could see the same event as a solar eclipse, with the disk of our fair planet Earth [ http://earthobservatory.nasa.gov/Newsroom/BlueMarble/ ] completely blocking out the Sun. For a moon-based observer's view, graphic artist Hana Gartstein (Haifa, Israel [ http://maps.google.com/maps?f=q&hl=en&q=haifa,+israel &layer=&ie=UTF8&om=1&z=7&ll=33.027088,34.865112 &spn=6.83228,13.886719&t=k ]) offers this composite illustration. In the cropped version of her picture, an Apollo 17 [ http://antwrp.gsfc.nasa.gov/apod/ap051210.html ] image of Earth is surrounded with a red-tinted haze as sunlight streams [ http://antwrp.gsfc.nasa.gov/apod/ap031121.html ] through the planet's dusty atmosphere. Earth's night [ http://antwrp.gsfc.nasa.gov/apod/ap050611.html ] side remains faintly visible, still illuminated by the dark, reddened Moon, but the disk of the Earth would appear almost four times the size of the Sun's disk, so the faint corona surrounding the Sun would be largely obscured. At the upper left, the Sun itself [ http://antwrp.gsfc.nasa.gov/apod/ap060330.html ] is just disappearing [ http://space.jpl.nasa.gov/cgi-bin/wspace?tbody=399&vbody=301 &month=3&day=3&year=2007&hour=22&minute=05&rfov=2 &fovmul=-1&bfov=30&porbs=1&showsc=1 ] behind the Earth's limb. |
|
Stereo Eros
| Title |
Stereo Eros |
| Explanation |
Get out your red/blue glasses [ http://photojournal.jpl.nasa.gov/Help/VendorList.html#Glasses ] and float next to asteroid 433 Eros [ http://neo.jpl.nasa.gov/cgi-bin/db?name=433 ], now over 220 million kilometers away! Orbiting the Sun once every 1.8 earth-years, asteroid Eros is [ http://near.jhuapl.edu/eros/history/eros_useful.html ] a diminutive 40 x 14 x 14 kilometer world of undulating horizons, craters, boulders [ http://antwrp.gsfc.nasa.gov/apod/ap000721.html ] and valleys. Its unsettling scale and bizarre shape are emphasized in this picture [ http://photojournal.jpl.nasa.gov/catalog/PIA02471 ] - a mosaic of images from the NEAR Shoemaker [ http://photojournal.jpl.nasa.gov/target/ Other?subselect=Spacecraft%3ANEAR+Shoemaker%3A ] spacecraft processed to yield a stereo anaglyphic [ http://faxmentis.org/html/ana-howto.html ] view. Along with dramatic [ http://en.wikipedia.org/wiki/Chiaroscuro#Gallery ] chiaroscuro [ http://studiochalkboard.evansville.edu/s-chiaro.html ], NEAR's 3-D imaging provided important measurements of the asteroid's landforms and structures, and clues to the origin of this city-sized chunk of solar system [ http://space.jpl.nasa.gov/ ]. The smallest features visible here are about 30 meters across. After spending a year in orbit around Eros, the historic Near Shoemaker spacecraft made the first ever landing on an asteroid's surface [ http://antwrp.gsfc.nasa.gov/apod/ap010824.html ] February 12, 2001. |
|
Saturn from Above
| Title |
Saturn from Above |
| Explanation |
This image of Saturn could not have been taken from Earth. No Earth [ http://antwrp.gsfc.nasa.gov/apod/ap000701.html ] based picture could possibly view the night side of Saturn [ http://en.wikipedia.org/wiki/Saturn ] and the corresponding shadow [ http://antwrp.gsfc.nasa.gov/apod/ap061016.html ] cast across Saturn's rings. Since Earth is much closer to the Sun than Saturn, only the day side of the planet is visible from the Earth. In fact, this image mosaic [ http://photojournal.jpl.nasa.gov/catalog/PIA08362 ] was taken in January by the robotic Cassini spacecraft [ http://saturn.jpl.nasa.gov/spacecraft/ ] now orbiting Saturn. The beautiful rings of Saturn are seen in full expanse, while cloud details [ http://antwrp.gsfc.nasa.gov/apod/ap051010.html ] are visible near the night-day terminator [ http://antwrp.gsfc.nasa.gov/apod/ap050611.html ] divide. |
|
Jupiter, Io, and Shadow
| Title |
Jupiter, Io, and Shadow |
| Explanation |
Just as planets orbit our Sun, Jupiter's Moons [ http://antwrp.gsfc.nasa.gov/apod/ap001118.html ] orbit Jupiter. Pictured above [ http://photojournal.jpl.nasa.gov/cgi-bin/PIAGenCatalogPage.pl?PIA02860 ] is the closest of Jupiter's Galilean Satellites [ http://www.jpl.nasa.gov/galileo/ganymede/discovery.html ], Io [ http://www.seds.org/nineplanets/nineplanets/io.html ], superposed in front of the giant planet it circles. To the left of Io [ http://www.hawastsoc.org/solar/eng/edu/moonio.htm ] is a dark spot that is its own shadow. The tremendous complexities that can be seen in Jupiter's banded, swirling atmosphere [ http://antwrp.gsfc.nasa.gov/apod/ap970310.html ] are being studied and may provide insight as to how Earth's atmosphere [ http://csep10.phys.utk.edu/astr161/lect/earth/atmosphere.html ] behaves. The above true-color contrast-enhanced image [ http://photojournal.jpl.nasa.gov/cgi-bin/PIAGenCatalogPage.pl?PIA02860 ] was taken [ http://ciclops.lpl.arizona.edu/ciclops/images_jupiter.html ] two weeks ago by the robot spacecraft Cassini [ http://quest.arc.nasa.gov/saturn/qa/cassini/ ], currently passing Jupiter [ http://antwrp.gsfc.nasa.gov/apod/jupiter.html ] and on its way to Saturn [ http://antwrp.gsfc.nasa.gov/apod/saturn.html ] in 2004. Engineers continue to study [ http://www.jpl.nasa.gov/jupiterflyby/news/mission_status.html ] the Cassini spacecraft [ http://www.jpl.nasa.gov/basics/cassini.htm ] itself to understand why it required more force than normal to turn one of its maneuvering wheels. |
|
Planetary Nebula Mz3: The An
…
| Title |
Planetary Nebula Mz3: The Ant Nebula |
| Explanation |
Why isn't this ant a big sphere? Planetary nebula [ http://www.noao.edu/jacoby/pn_gallery.html ] Mz3 is being cast off by a star similar to our Sun [ http://www.nineplanets.org/sol.html ] that is, surely, round. Why then would the gas that is streaming away create an ant [ http://www.discovery.com/cams/ant/learn.html ]-shaped nebula that is distinctly not round? Clues might include [ http://hubble.esa.int/hubble/news/ index.cfm?oid=25994 ] the high 1000-kilometer per second speed of the expelled gas, the light-year [ http://starchild.gsfc.nasa.gov/docs/StarChild/ questions/question19.html ] long length of the structure, and the magnetism [ http://www.wondermagnet.com/dev/magfaq.html ] of the star visible above [ http://heritage.stsci.edu/public/2001feb/display.html ] at the nebula's center. One possible answer is that Mz3 [ http://heritage.stsci.edu/public/2001feb/table.html ] is hiding a second, dimmer star that orbits close [ http://antwrp.gsfc.nasa.gov/apod/ap991219.html ] in to the bright star. A competing hypothesis holds that the central star's own spin and magnetic field [ http://antwrp.gsfc.nasa.gov/apod/ap980629.html ] are channeling the gas. Since the central star appears to be so similar to our own Sun, astronomers [ http://www.aas.org/%7Eeducation/career.html ] hope that increased understanding of the history of this giant space ant [ http://www.ag.ohio-state.edu/~ohioline/hyg-fact/2000/2064.html ] can provide useful insight into the likely future of our own Sun [ http://antwrp.gsfc.nasa.gov/apod/sun.html ] and Earth [ http://antwrp.gsfc.nasa.gov/apod/earth.html ]. |
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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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