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Earth and Moon of Goddard Space Flight Center (GSFC) and Arizona
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Stereo Saturn
| Title |
Stereo Saturn |
| Explanation |
Get out your red/blue glasses [ http://img.arc.nasa.gov/archive/desert96/redblue.html ] and launch [ http://antwrp.gsfc.nasa.gov/apod/ap971016.html ] yourself into this stereo [ http://cass.jsc.nasa.gov/research/stereo_atlas/SS3D.HTM ] picture of Saturn! The picture is actually composed from two images recorded weeks apart by the Voyager 2 spacecraft [ http://vraptor.jpl.nasa.gov/voyager/voyager_fs.html ] during its visit to [ http://nssdc.gsfc.nasa.gov/planetary/voyager.html ] the Saturnian System in August of 1981. Traveling at about 35,000 miles per hour, the spacecraft's changing viewpoint from one image to the next produced this exaggerated but pleasing stereo effect [ http://antwrp.gsfc.nasa.gov/apod/ap970404.html ]. Saturn is the second largest planet [ http://seds.lpl.arizona.edu/nineplanets/nineplanets/saturn.html ] in the Solar System, after Jupiter. Its spectacular ring system [ http://ringmaster.arc.nasa.gov/saturn/saturn.html ] is so wide that it would span the space between the Earth and Moon. Although they look solid here, Saturn's [ http://antwrp.gsfc.nasa.gov/apod/ap000129.html ] rings consist of individually orbiting bits of ice and rock ranging in size from grains of sand to barn-sized boulders. |
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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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Halo and Hexagons
| Title |
Halo and Hexagons |
| Explanation |
As a bright November Moon lit up the night sky last week, Gil Esquerdo spotted this lovely Moon halo overhead [ http://www.atoptics.co.uk/ ] at the Whipple Observatory on Mt. Hopkins, Arizona. In the foreground, the structure and individual component mirrors of Whipple's 10 meter gamma-ray telescope [ http://veritas.sao.arizona.edu/old/ VERITAS_whipple_photos.html ] actually block direct light from the lunar disk, emphasizing the halo in this dramatic view. The halo was caused by ice crystals in the thin high clouds above the observatory - crystals that are hexagonal in shape [ http://hyperphysics.phy-astr.gsu.edu/hbase/atmos/ moonhalo.html ] and produce the characteristic ring of light with a 22 degree radius. In fact, the ice crystal shapes are much like the flat, hexagonal mirrors of the specialized [ http://antwrp.gsfc.nasa.gov/apod/ap041015.html ] telescope in the picture. Used together the mirrors can collect brief flashes of optical light caused by high-energy gamma-rays impacting [ http://imagine.gsfc.nasa.gov/docs/science/how_l2/ cerenkov.html ] Earth's atmosphere. |
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Mountains of Titan
| Title |
Mountains of Titan |
| Explanation |
Peering through [ http://www.jpl.nasa.gov/news/news.cfm?release=2006-147 ] the thick, hazy atmosphere of Saturn's largest moon, an infrared camera onboard the Cassini [ http://saturn.jpl.nasa.gov/home/index.cfm ] spacecraft recorded this view of the tallest mountains ever seen on Titan [ http://antwrp.gsfc.nasa.gov/apod/ap060508.html ]. Captured during a flyby in late October, the high resolution, false-color mosaic [ http://photojournal.jpl.nasa.gov/catalog/PIA09032 ] shows a mountain range about 150 kilometers long and about 1.5 kilometers high - likened to the Sierra Nevada [ http://en.wikipedia.org/wiki/Sierra_Nevada_(US) ] mountain range of the western United States, planet Earth [ http://earthobservatory.nasa.gov/Newsroom/ NewImages/images.php3?img_id=11270 ]. Along Titan's mountain ridges lie bright deposits, thought to be methane [ http://www.astrobio.net/news/article1886.html ] snow or other organic material. The icy [ http://antwrp.gsfc.nasa.gov/apod/ap050610.html ] mountains of Titan were probably formed like Earth's mid-ocean ridges, from material welling up [ http://www.pbs.org/wgbh/aso/tryit/tectonics/ divergent.html ] to fill gaps created as surface tectonic plates [ http://www.ucmp.berkeley.edu/geology/tectonics.html ] spread apart. |
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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. |
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Double Asteroid 90 Antiope
| Title |
Double Asteroid 90 Antiope |
| Explanation |
This eight-frame animation is based on the first ever images [ http://www.boulder.swri.edu/~merline/press/ ] of a double asteroid [ http://www.boulder.swri.edu/~merline/press/release.txt ]! Formerly thought to be a single enormous chunk of rock, asteroid 90 Antiope [ http://cfa-www.harvard.edu/iau/lists/ NumberedMPs00001.html ] resides in the solar system's [ http://space.jpl.nasa.gov/ ] main asteroid belt [ http://seds.lpl.arizona.edu/nineplanets/nineplanets/ asteroids.html ] between Mars and Jupiter. Now, these premier images reveal Antiope to actually consist of two 50 mile wide asteroids separated by about 100 miles. Like weights on each end of an elastic string, the pair mutually orbit [ http://hyperphysics.phy-astr.gsu.edu/hbase/ orbv.html#bo ] their center of mass, or balance point in the space between them, once every 16.5 hours. Binary asteroids and asteroids with moons [ http://antwrp.gsfc.nasa.gov/apod/ap991014.html ] are believed to be rare, but observations of their orbits allow a direct determination of asteroid masses and densities. Surprisingly, Antiope and known [ http://www.cfht.hawaii.edu/News/PR_001026/ ] asteroid-moon [ http://antwrp.gsfc.nasa.gov/apod/ap990807.html ] systems are found to have densities closer to ice than rock, despite their relatively dark and unreflective surfaces. These sharp images were made at the Keck Observatory atop the Hawaiian volcano Mauna Kea using newly developed adaptive optics [ http://www.mtwilson.edu/Science/ AdapOpt/Overview/ ] technology to overcome the blurring effect [ http://antwrp.gsfc.nasa.gov/apod/ap000725.html ] of Earth's atmosphere. |
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Io: Moon Over Jupiter
| Title |
Io: Moon Over Jupiter |
| Explanation |
How big is the Jovian moon Io [ http://www.seds.org/nineplanets/ nineplanets/io.html ]? The most volcanic body [ http://volcano.und.nodak.edu/vwdocs/planet_volcano/ other_worlds.html ] in the Solar System, Io (usually pronounced "EYE-oh") is 3,600 kilometers in diameter, about the size of planet Earth's single large natural satellite [ http://antwrp.gsfc.nasa.gov/apod/ap010127.html ]. Gliding past Jupiter [ http://www.jpl.nasa.gov/jupiterflyby/ ] at the turn of the millennium, the Cassini spacecraft captured this awe inspiring view [ http://ciclops.lpl.arizona.edu/ciclops/images_jupiter.html ] of active Io [ http://www.jpl.nasa.gov/galileo/moons/io.html ] with the largest [ http://www.seds.org/nineplanets/nineplanets/ datamax.html ] gas giant as a backdrop, offering a stunning demonstration of the ruling planet's relative size [ http://nssdc.gsfc.nasa.gov/planetary/factsheet/ jupiterfact.html ]. Although in the picture Io [ http://photojournal.jpl.nasa.gov/cgi-bin/ PIAGenCatalogPage.pl?PIA02879 ] appears to be located just in front of the swirling Jovian clouds, Io hurtles around its orbit once every 42 hours at a distance of 420,000 kilometers or so from the center of Jupiter [ http://nssdc.gsfc.nasa.gov/planetary/factsheet/ joviansatfact.html ]. That puts it nearly 350,000 kilometers above Jupiter's cloud tops [ http://antwrp.gsfc.nasa.gov/apod/ap010215.html ], roughly equivalent to the distance between Earth and Moon [ http://antwrp.gsfc.nasa.gov/apod/ap980904.html ]. The Cassini spacecraft [ http://www.jpl.nasa.gov/cassini/english/spacecraft/ ] itself was about 10 million kilometers from Jupiter when recording the image data. |
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Red, White, and Blue Sky
| Title |
Red, White, and Blue Sky |
| Explanation |
Contrasting colors in this beautiful sunset sky [ http://www.schursastrophotography.com/10dastro/ vensat070107.html ] were captured on June 30 from Clear Creek Canyon Observatory in central Arizona, USA. The twilight scene includes brilliant [ http://www.digitalsky.org.uk/venus/ shadow-of-venus.html ] Venus as the evening star [ http://www.johnpratt.com/items/astronomy/eve_morn.html ], with a bright Saturn just above it, shining through thin clouds. The two wandering [ http://antwrp.gsfc.nasa.gov/apod/ap070407.html ] planets [ http://antwrp.gsfc.nasa.gov/apod/ap010601.html ] were a mere 1 degree apart or so, about twice the width of the full Moon rising above the eastern horizon on the other side of the sky. In fact, such serene skyviews [ http://www.spaceweather.com/ ] were possible from all over planet Earth as Venus and Saturn approached a conjunction [ http://en.wikipedia.org/wiki/Astronomical_conjunction# Conjunctions_of_planets_in_right_ascension_2005-2020 ]. Regulus, alpha star of the constellation Leo [ http://en.wikipedia.org/wiki/Leo_(constellation) ], is above and to the left of the close planetary pairing. At dusk, lights in tonight's sky will also feature Venus and Saturn low in the west and separated by about 2 degrees. |
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Astronomer's Moon
| Title |
Astronomer's Moon |
| Explanation |
Jupiter is [ http://www.nineplanets.org/jupiter.html ] an astronomer's planet -- its large size and contrasting global cloud belts and zones [ http://antwrp.gsfc.nasa.gov/apod/ap030906.html ] allow detailed studies with a range of earthbound telescopes [ http://www.lpl.arizona.edu/alpo/ ]. On the other hand, most telescopic views of Jupiter's moons [ http://antwrp.gsfc.nasa.gov/apod/ap030227.html ] usually show only featureless, tantalizing points of light hovering near the ruling gas giant. But this impressive picture from a small, ground-based telescope reveals a stunning amount of detail [ http://www.cloudynights.com/ubbthreads/showflat.php/Cat/0/ Number/1752001/page/0/view/collapsed/sb/5/o/all/fpart/1 ] on Ganymede, a jovian moon about the same size as Earth's moon but at least 1,500 times farther away. The image was carefully constructed by combining and processing only the 409 sharpest frames from a total of 10,000 recorded at 30 frames per second by a digital camera. Ganymede's [ http://www.nineplanets.org/ganymede.html ] radius is about 2,600 kilometers indicating that the surface markings [ http://space.jpl.nasa.gov/cgi-bin/wspace?tbody=503&vbody=399 &month=6&day=30&year=2007&hour=20&minute=05&rfov=2&fovmul=-1&bfov=30 &porbs=1&showsc=1 ] visible are as small as around 900 kilometers across. |
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Welcome to the Moon Hotel
| Title |
Welcome to the Moon Hotel |
| Explanation |
The most detailed proposal [ http://www.rombaut.nl/ ] so far for a hotel and resort [ http://antwrp.gsfc.nasa.gov/apod/ap001209.html ] destination on the Moon [ http://seds.lpl.arizona.edu/nineplanets/nineplanets/ luna.html ] (!) has been prepared by Dutch [ http://www.xs4all.nl/~carlkop/maanhotel/lunatic.html ] architect Hans-Jurgen Rombaut. The harsh lunar environment [ http://www.frc.ri.cmu.edu/projects/lri/Luna/report/ des_approach.html#REF61557 ] posed serious design challenges [ http://members.aol.com/dsfportree/ explore.htm ] but the Moon's low, one-sixth-Earth gravity [ http://www.windows.ucar.edu/cgi-bin/tour_def/earth/ moons_and_rings.html ], and the absence of wind were an architectural boon allowing a much more slender and fragile-looking building than would have been possible on Earth [ http://www.bc.edu/bc_org/avp/cas/fnart/arch/ contents_europe.html ]. Illustrated here, the structure's two 160 meter high needle-like towers soar over [ http://www.rombaut.nl/engindex2.htm ] the rim of a deep canyon as planet Earth hangs in the lunar sky [ http://snoopy.gsfc.nasa.gov/~lunartel/ ]. To shield the interior, Rombaut designed 50 centimeter thick walls with two outer layers of Moon rock and a 35 centimeter layer of water [ http://nssdc.gsfc.nasa.gov/planetary/ice/ice_moon.html ] held between glass planes. The water absorbs energetic cosmic rays [ http://www.hps.org/ publicinformation/ate/q753.html ] and along with the rock helps keep the temperature constant. Windows are framed as holes in the rock layers. Construction materials [ http://www.seds.org/~rme/lunar.html ] are intended to be manufactured on the Moon [ http://lunar.arc.nasa.gov/ ] itself. This Moon Hotel design is welcomed by the international Lunar Explorers Society, LUNEX [ http://www.lunarexplorers.org ], who hope to construct a robotic Moon base [ http://ads.harvard.edu/books/lbsa/ ] by 2015, ultimately [ http://members.aol.com/dsfportree/explore.htm ] supporting a lunar village by 2040. |
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VERITAS and Venus
| Title |
VERITAS and Venus |
| Explanation |
Early morning risers and late to bed astronomers have recently enjoyed bright planets [ http://science.nasa.gov/headlines/y2007/02nov_nov5.htm ] in predawn skies, with brilliant Venus [ http://www.avertedimagination.com/img_pages/ morning_star.html ] above the eastern horizon. On November 5, Venus was joined by the waning crescent Moon. This self-portrait by astronomer Larry Ciupik captures the lovely pairing of the two brightest celestial beacons on the scene, though the Moon, right of Venus, is strongly over exposed. Included at the far left in the 30 second exposure is the bright streak of the International Space Station [ http://antwrp.gsfc.nasa.gov/apod/ap070625.html ] still docked with shuttle orbiter Discovery [ http://www.nasa.gov/mission_pages/shuttle/ main/index.html ]. Together in Earth orbit, the spacefaring [ http://antwrp.gsfc.nasa.gov/apod/ap070628.html ] combination was momentarily the third brightest sky light in view [ http://spaceflight.nasa.gov/realdata/sightings/index.html ]. In dim silhouette, a multi-mirrored unit of the Very Energetic Radiation Imaging Telescope Array System (VERITAS [ http://veritas.adlerplanetarium.org/home.shtml ]) is also visible in the foreground. VERITAS operates at the Whipple Observatory near Tucson, Arizona to detect high-energy gamma-rays from the cosmos [ http://veritas.adlerplanetarium.org/science/ ]. |
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Mars in View
| Title |
Mars in View |
| Explanation |
Very good telescopic views of Mars [ http://mars.jpl.nasa.gov/allabout/nightsky/ viewing-tips-2007.html ] can be expected in the coming weeks as the Red Planet [ http://www.uapress.arizona.edu/onlinebks/mars/contents.htm ] nears opposition on December 24th. Of course [ http://antwrp.gsfc.nasa.gov/apod/ap060422.html ], opposition means opposite the Sun in planet Earth's sky - an arrangement [ http://mars.jpl.nasa.gov/allabout/nightsky/nightsky03.html ] that occurs every 26 months for Mars. Because of Mars' [ http://nssdc.gsfc.nasa.gov/planetary/factsheet/marsfact.html ] more elliptical orbit, the actual date of closest approach to Earth will be December 18, when Mars will be within about 88 million kilometers of our fair planet. Situated in the constellation Gemini and rising after evening twilight, the bright, ruddy disk of Mars will reach nearly 16 arcseconds [ http://coolcosmos.ipac.caltech.edu/cosmic_classroom/ cosmic_reference/angular.html ] in diameter (about 1/100th the diameter of the Full Moon). In this already exceptional image taken on November 18, north is down and surface markings around the sprawling, dark, albedo feature Syrtis Major [ http://photojournal.jpl.nasa.gov/catalog/PIA01592 ] are remarkably clear. The image was recorded with a video camera and filters on a 1 meter telescope at Pic Du Midi [ http://en.wikipedia.org/wiki/Pic_du_Midi_de_Bigorre ], a mountain top observatory in the French Pyrenees. NASA launched the Phoenix [ http://phoenix.lpl.arizona.edu/mission.php ] lander to Mars in August, scheduled to arrive in May 2008. |
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Asteroid 2007 TU24 Passes th
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| Title |
Asteroid 2007 TU24 Passes the Earth |
| Explanation |
Asteroid 2007 TU24 passed by the Earth yesterday, posing no danger. The space rock, estimated [ http://www.nasa.gov/topics/solarsystem/features/asteroid-20080125.html ] to be about 250 meters across, coasted by just outside the orbit of Earth's Moon. The passing was not very unusual [ http://antwrp.gsfc.nasa.gov/apod/ap050417.html ] -- small rocks strike Earth daily, and in 2003 a rock the size of a bus passed inside the orbit of the Moon, being detected only after passing [ http://antwrp.gsfc.nasa.gov/apod/ap031015.html ]. TU24 was notable partly because it was so large. Were TU24 [ http://en.wikipedia.org/wiki/TU24 ] to have struck land, it might have caused a magnitude [ http://www.geo.mtu.edu/UPSeis/magnitude.html ] seven earthquake [ http://www.youtube.com/watch?v=19fMs633Td4 ] and left a city-sized crater [ http://antwrp.gsfc.nasa.gov/apod/ap990711.html ]. A perhaps larger danger would have occurred were TU24 [ http://www.planetary.org/blog/article/00001309/ ] to have struck the ocean and raised a large tsunami [ http://en.wikipedia.org/wiki/Tsunami ]. This radar image [ http://www.jpl.nasa.gov/news/news.cfm?release=2008-014 ] was taken two days ago. The Arecibo Radio Telescope [ http://antwrp.gsfc.nasa.gov/apod/ap981129.html ] in Puerto Rico [ http://en.wikipedia.org/wiki/Puerto_Rico ] broadcast radar that was reflected by the asteroid and then recorded by the Byrd Radio Telescope [ http://www.gb.nrao.edu/gbt/ ] in Green Bank [ http://www.nrao.edu/administration/personnel_office/greenbank.shtml ], West Virginia [ http://en.wikipedia.org/wiki/West_Virginia ]. The resulting image [ http://www.jpl.nasa.gov/news/news.cfm?release=2008-014 ] shows TU24 to have an oblong and irregular shape. TU24 [ http://www.nasa.gov/topics/solarsystem/features/asteroid-20080128-clips.html ] was discovered only three months ago, indicating that other potentially hazardous asteroids [ http://neo.jpl.nasa.gov/ca/ ] might lurk in our Solar System [ http://space.jpl.nasa.gov/ ] currently undetected. Objects like TU24 [ http://www.space.com/scienceastronomy/080128-asteroid-radar.html ] are hard to detect because they are so faint and move [ http://antwrp.gsfc.nasa.gov/apod/ap060328.html ] so fast. Humanity's ability to scan the sky to detect, catalog, and analyze such objects has increased notably [ http://www.lpl.arizona.edu/css/ ] in recent years. |
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Ski Enceladus
| Title |
Ski Enceladus |
| Explanation |
A small inner moon of Saturn [ http://csep10.phys.utk.edu/astr161/lect/saturn/moons.html ], Enceladus is only about 500 kilometers in diameter. But the cold, distant world does reflect over 90 percent of the sunlight it receives, giving its surface about the same reflectivity as new-fallen snow. Seen here [ http://photojournal.jpl.nasa.gov/cgi-bin/ PIAGenCatalogPage.pl?PIA00347 ] in a mosaic of Voyager [ http://vraptor.jpl.nasa.gov/voyager/ vgrsat_fs.html ] 2 images from 1981, Enceladus [ http://solarsystem.nasa.gov/features/planets/saturn/ enceladus.html ] shows a variety of surface features and very few impact craters - indicating that it is an active world even though this ice moon should have completely cooled off long ago [ http://www.sciam.com/explorations/010697sagan/ 010697sagan1.html ]. In fact the fresh, resurfaced appearance of Enceladus suggests that an internal mechanism, perhaps driven by tidal pumping, generates heat and supplies liquid water to geysers or water volcanos [ http://pirlwww.lpl.arizona.edu/HIIPS/ Cryovolcanism/ ]. Since Enceladus orbits within the tenuous outer E [ http://www.astro.spbu.ru/staff/dikarev/valery/ering.html ] ring [ http://ringmaster.arc.nasa.gov/saturn/ saturn.html#IMAGES ] of Saturn, the moon's surface may be kept snow-bright as it is continuously bombarded with icy ring particles. Eruptions [ http://www.jpl.nasa.gov/cassini/Mission/pix/ enceladus_lg.gif ] on Enceladus itself would in turn supply material to the E ring. Interplanetary [ http://www.jpl.nasa.gov/cassini/Mission/ ] ski [ http://antwrp.gsfc.nasa.gov/apod/ap990401.html ] bums take note: tiny Enceladus has only about one hundredth the surface gravity of planet Earth [ http://photojournal.jpl.nasa.gov/cgi-bin/ PIAGenCatalogPage.pl?PIA03439 ]. |
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Comet Ikeya-Zhang
| Title |
Comet Ikeya-Zhang |
| Explanation |
Comet Ikeya-Zhang [ http://cometography.com/lcomets/2002c1.html ] is presently heading north in planet Earth's sky [ http://encke.jpl.nasa.gov/images/02C1/ c2002c1chart.jpg ], framed by stars of the constellation Cetus. The comet was discovered [ http://cfa-www.harvard.edu/iauc/07800/ 07812.html ] as a faint, telescopic object [ http://encke.jpl.nasa.gov/RecentObs.html#02C1 ] near the western horizon on the evening of February 1st independently by Kaoru Ikeya [ http://comets.amsmeteors.org/comets/ lcomets/1965s1.html ] of Shizuoka prefecture, Japan, Daqing Zhang in Henan province, China, and later by [ http://cfa-www.harvard.edu/iauc/07800/07813.html ] observer Paulo Raymundo of Salvador, Brazil. But Ikeya-Zhang [ http://skyandtelescope.com/observing/objects/comets/ article_477_1.asp ] is expected to brighten significantly and in March and April could become visible to the unaided eye. This picture, taken near Tucson, Arizona, USA on the evening of February 9th, covers a field a bit less than the width of the full moon showing the comet's [ http://encke.jpl.nasa.gov/define.html ] condensed coma [ http://www.ifa.hawaii.edu/faculty/jewitt/ coma.html ] and narrow, developing tail [ http://antwrp.gsfc.nasa.gov/apod/ap001227.html ]. Ikeya-Zhang should pass closest to the Sun (perihelion) on March 18 at a point roughly midway [ http://encke.jpl.nasa.gov/images/02C1/ ikeyaorbit.jpg ] between the orbits of Mercury and Venus. Based on preliminary calculations of this comet's orbit, Ikeya-Zhang [ http://cfa-www.harvard.edu/iau/Ephemerides/Comets/ 2002C1.html ] is suspected of being a periodic comet, returning to the inner Solar System every 500 years or so. In fact, it is "speculated" that Ikeya-Zhang may be directly connected with a historic bright comet [ http://ssd.jpl.nasa.gov/great_comets.html ] seen in 1532. |
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Venus: Earth's Sister Planet
| Title |
Venus: Earth's Sister Planet |
| Explanation |
This picture in visible light was taken by the Galileo [ http://nssdc.gsfc.nasa.gov/planetary/galileo.html ] spacecraft. Venus [ http://seds.lpl.arizona.edu/nineplanets/nineplanets/venus.html ] is very similar to Earth [ http://antwrp.gsfc.nasa.gov/apod/ap950622.html ] in size and mass - and so is sometimes referred to as Earth's sister planet - but Venus has a quite different climate. Venus' [ http://www.c3.lanl.gov/~cjhamil/SolarSystem/venus.html ] thick clouds and closeness to the Sun [ http://antwrp.gsfc.nasa.gov/apod/ap950813.html ] (only Mercury [ http://antwrp.gsfc.nasa.gov/apod/ap950814.html ] is closer) make it the hottest planet - much hotter than the Earth. Humans could not survive there, and no life of any sort has ever been found. When Venus [ http://nssdc.gsfc.nasa.gov/photo_gallery/PhotoGallery-Venus.html ] is visible it is usually the brightest object in the sky after the Sun and the Moon. More than 20 spacecraft have visited Venus including Venera 9, which landed on the surface, and Magellan [ http://stardust.jpl.nasa.gov/mveg/guide.html ], which used radar to peer through the clouds and make a map of the surface. There are still many things about Venus's unusual atmosphere that astronomers don't understand. Tomorrow's picture: Uranus: The Tilted Planet |
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Ganymede: Moonquake World
| Title |
Ganymede: Moonquake World |
| Explanation |
Ganymede [ http://seds.lpl.arizona.edu/nineplanets/nineplanets/ganymede.html ] probably undergoes frequent ground shaking events not unlike terrestrial earthquakes. Ganymede [ http://www.c3.lanl.gov/~cjhamil/SolarSystem/ganymede.html ], the largest moon of Jupiter [ http://antwrp.gsfc.nasa.gov/apod/ap950625.html ] and the Solar System [ http://antwrp.gsfc.nasa.gov/apod/ap950819.html ], has a thick outer coating of water ice. Passing Voyager spacecraft found a large number of cracks and grooves in the ice so it is thought that Ganymede, like the Earth [ http://antwrp.gsfc.nasa.gov/apod/ap950622.html ], has large shifting surface masses called tectonic plates. Ganymede was discovered by Galileo [ http://galileo.imss.firenze.it/museo/4/index.html ] and Marius [ http://seds.lpl.arizona.edu/billa/tnp/help.html#M ] in 1610, and is larger than the planets Mercury and Pluto. The NASA spacecraft Galileo [ http://www.jpl.nasa.gov/galileo/ ] is scheduled to arrive at Jupiter is December of 1995. Tomorrow's picture: Europa: Ancient Water World |
|
Europa: Ancient Water World
| Title |
Europa: Ancient Water World |
| Explanation |
Beneath the cold icy surface of Jupiter [ http://antwrp.gsfc.nasa.gov/apod/ap950625.html ]'s moon Europa [ http://seds.lpl.arizona.edu/nineplanets/nineplanets/europa.html ] are probably the only oceans of water in our Solar System [ http://antwrp.gsfc.nasa.gov/apod/ap950819.html ] outside of Earth [ http://antwrp.gsfc.nasa.gov/apod/ap950622.html ]. These oceans, possibly 50 kilometers deep, might also be the most likely local place to find extra-terrestrial life. Europa [ http://www.c3.lanl.gov/~cjhamil/SolarSystem/europa.html ]'s smooth surface is unlike any other known planet or moon, giving evidence for relatively few craters or mountains. Europa was discovered by Galileo [ http://galileo.imss.firenze.it/museo/4/index.html ] and Marius [ http://seds.lpl.arizona.edu/billa/tnp/help.html#M ] in 1610. The NASA spacecraft Galileo [ http://www.jpl.nasa.gov/galileo/ ] is scheduled to arrive at Jupiter in December of 1995. Tomorrow's picture: Callisto: Dark Smashed Iceball |
|
Earth's Moon, A Familiar Fac
…
| Title |
Earth's Moon, A Familiar Face |
| Explanation |
The above mosaic of the Earth's Moon [ http://seds.lpl.arizona.edu/nineplanets/nineplanets/luna.html ] was compiled from photos taken by the spacecraft Clementine [ http://nssdc.gsfc.nasa.gov/planetary/clementine.html ] in 1994. This image represents the side of the Moon familiar to Earth dwellers. The Moon [ http://www.c3.lanl.gov/~cjhamil/SolarSystem/moon.html ] revolves around the Earth [ http://antwrp.gsfc.nasa.gov/apod/ap950622.html ] about once every 28 days. Since its rate of rotation about its axis is also once in 28 days, it always keeps the same face toward the Earth. As the Moon travels around its orbit, the Earth based view of the half of the Moon [ http://nssdc.gsfc.nasa.gov/photo_gallery/photogallery-moon.html ] that faces the Sun [ http://antwrp.gsfc.nasa.gov/apod/ap950813.html ] changes causing the regular monthly progression of Lunar phases. Humans first crashed a spacecraft [ http://nssdc.gsfc.nasa.gov/cgi-bin/database/www-nmc?59-014A ] into the Moon in 1959, but the first humans to reach the Moon landed [ http://www.ksc.nasa.gov/history/apollo/apollo-11/apollo-11.html ] in 1969. There are now golf balls [ http://ees5-www.lanl.gov/APOLLO/a14.clsout2.html ] on the Moon. Tomorrow's picture: Ganymede: Moonquake World |
|
Titan: Saturn's Smog Moon
| Title |
Titan: Saturn's Smog Moon |
| Explanation |
The largest moon of Saturn [ http://antwrp.gsfc.nasa.gov/apod/ap950705.html ] is a rare wonder. Titan is the only one of Saturn [ http://seds.lpl.arizona.edu/nineplanets/nineplanets/titan.html ]'s moons with an atmosphere, and one of only two moons in the Solar System [ http://antwrp.gsfc.nasa.gov/apod/ap950819.html ] with this distinction (Neptune [ http://antwrp.gsfc.nasa.gov/apod/ap950817.html ]'s Triton [ http://antwrp.gsfc.nasa.gov/apod/ap950805.html ] is the other). Titan [ http://www.c3.lanl.gov/~cjhamil/SolarSystem/titan.html ]'s thick cloudy atmosphere is mostly nitrogen, like Earth [ http://antwrp.gsfc.nasa.gov/apod/ap950622.html ]'s, but contains much higher percentages of "smog-like" chemicals such as methane and ethane. The smog may be so thick that it actually rains "gasoline-like" liquids. The organic nature of some of the chemicals found in Titan's atmosphere cause some to speculate that Titan may harbor life! Because of its thick cloud cover, however, Titan's actual surface properties remain mysterious. Voyager [ http://vraptor.jpl.nasa.gov/voyager/voyager.html ] 1 flew by in 1980 taking the above picture, and recently much has been learned from Hubble Space Telescope observations [ http://www.stsci.edu/pubinfo/PR/94/55.html ]. The Cassini mission [ http://www.jpl.nasa.gov/mip/cassini.html ] currently scheduled for launch in 1997 will map Titan's surface, helping to solve some of its mysteries. |
|
Dione's Lagrange Moon Helene
| Title |
Dione's Lagrange Moon Helene |
| Explanation |
Saturn [ http://antwrp.gsfc.nasa.gov/apod/ap950705.html ]'s moon Helene [ http://www.c3.lanl.gov/~cjhamil/SolarSystem/helene.html ] is very unusual in that it circles Saturn [ http://antwrp.gsfc.nasa.gov/apod/ap950801.html ] near the orbit of a bigger moon: Dione [ http://antwrp.gsfc.nasa.gov/apod/ap951009.html ]. Helene is situated in what is called a "Lagrange point" of Dione - a place of stability created by Dione's gravity. Were Helene [ http://seds.lpl.arizona.edu/nineplanets/nineplanets/dione.html#helene ] to stray slightly from its orbit 1/6 ahead of Dione, the larger moon's gravity would cause Helene to move back toward the Lagrange point. Many massive orbital bodies have stable Lagrange points, including the Earth and Moon. Helene was discovered from the ground by P. Laques & J. Lecacheux in 1980. The photograph above was taken by Voyager 2 as it passed Saturn in 1981. NASA's Cassini [ http://newproducts.jpl.nasa.gov/calendar/cassini.html ] mission to Saturn is currently scheduled for launch in October 1997. |
|
Rhea: Saturn's Second Larges
…
| Title |
Rhea: Saturn's Second Largest Moon |
| Explanation |
Rhea [ http://seds.lpl.arizona.edu/nineplanets/nineplanets/rhea.html ] is the second largest moon of Saturn [ http://antwrp.gsfc.nasa.gov/apod/ap950705.html ], behind Titan [ http://antwrp.gsfc.nasa.gov/apod/ap950923.html ], and the largest without an atmosphere. It is composed mostly of water ice, but has a small rocky core. Rhea [ http://www.c3.lanl.gov/~cjhamil/SolarSystem/rhea.html ]'s rotation and orbit are locked together (just like Earth's Moon) so that one side always faces Saturn. A consequence of this is that one side always leads the other. Rhea's leading surface is much more heavily cratered than its trailing surface. The above photograph was taken with the Voyager 1 spacecraft in 1980. |
|
Neptune's Moon Proteus
| Title |
Neptune's Moon Proteus |
| Explanation |
Proteus is the second largest moon of Neptune [ http://antwrp.gsfc.nasa.gov/apod/ap950817.html ] behind the mysterious Triton [ http://antwrp.gsfc.nasa.gov/apod/ap950805.html ]. Proteus was discovered only in 1982 by the Voyager 2 spacecraft. This is unusual since Neptune has a smaller moon - Nereid - which was discovered 33 years earlier from Earth. The reason Proteus [ http://seds.lpl.arizona.edu/nineplanets/nineplanets/proteus.html ] was not discovered sooner is that its surface is very dark and it orbits much closer to Neptune. Proteus [ http://www.c3.lanl.gov/~cjhamil/SolarSystem/proteus.html ] has an odd box-like shape and were it even slightly more massive, its own gravity would cause it to reform itself into a sphere. |
|
Asteroids in the Distance
| Title |
Asteroids in the Distance |
| Explanation |
Rocks from space hit Earth every day. The larger the rock, though, the less often Earth is struck. Many kilograms of space dust pitter to Earth daily. Larger bits appear initially as a bright meteor [ http://www.seds.org/nineplanets/nineplanets/meteorites.html ]. Baseball-sized rocks and ice-balls streak through our atmosphere daily, most evaporating quickly to nothing. Significant threats [ http://neo.jpl.nasa.gov/risk/ ] do exist for rocks near 100 meters in diameter, which strike the Earth [ http://antwrp.gsfc.nasa.gov/apod/ap990711.html ] roughly every 1000 years. An object this size could cause significant tidal waves were it to strike an ocean, potentially devastating even distant shores. A collision with a massive asteroid [ http://antwrp.gsfc.nasa.gov/apod/ap970629.html ], over 1 km across, is more rare [ http://antwrp.gsfc.nasa.gov/apod/ap980313.html ], occurring typically millions of years apart, but could have truly global consequences [ http://neo.jpl.nasa.gov/risk/doc/sentry.html ]. Many asteroids remain undiscovered [ http://spacewatch.lpl.arizona.edu/ ]. In fact, one was discovered in 1998 as the long blue streak in the above archival image [ http://oposite.stsci.edu/pubinfo/pr/1998/10/ ] taken by the Hubble Space Telescope. Last week [ http://neo.jpl.nasa.gov/ ], the small 100-meter asteroid 2002 MN [ http://SkyandTelescope.com/news/current/article_641_1.asp ] was discovered only after it whizzed by the Earth, passing well within the orbit of the Moon. 2002 MN [ http://neo.jpl.nasa.gov/risk/2002mn.html ] passed closer than any asteroid since 1994 XM1 [ http://astrowww.phys.uvic.ca/media/press/1.htm ]. A collision [ http://antwrp.gsfc.nasa.gov/apod/ap990425.html ] with a large asteroid would not affect Earth's orbit so much as raise dust that would affect Earth's climate [ http://www.permanent.com/a_impact.htm ]. One likely result is a global extinction of many species of life, possibly dwarfing the ongoing extinction occurring now [ http://www.ran.org/info_center/factsheets/03b.html ]. |
|
Lunar Module at Taurus-Littr
…
| Title |
Lunar Module at Taurus-Littrow |
| Explanation |
Can the Hubble Space Telescope [ http://hubblesite.org/ ] take a picture that shows the Apollo lunar modules [ http://users.specdata.com/home/pullo/lm_mis1.htm ] on the Moon? With its 2.4 meter diameter mirror [ http://hubblesite.org/sci.d.tech/nuts_.and._bolts/optics/ ], the smallest object that the Hubble can resolve [ http://astrosun.tn.cornell.edu/courses/astro201/ purpose.htm ] at the Moon's distance [ http://www.nineplanets.org/luna.html ] of around 400,000 kilometers is about 80 meters across. So, from low Earth orbit even Hubble's sharp vision can not image the Apollo lunar module descent stages, at most a few meters across, left behind [ http://antwrp.gsfc.nasa.gov/apod/ap981213.html ] at the lunar landing sites [ http://nssdc.gsfc.nasa.gov/planetary/lunar/ apolloland.html ]. A space telescope over ten times the size of Hubble could ... or a much smaller telescope in close lunar orbit. In fact, this picture does just resolve Apollo 17's Lunar Module, Challenger [ http://antwrp.gsfc.nasa.gov/apod/ap020105.html ], and its shadow on the cratered floor [ http://antwrp.gsfc.nasa.gov/apod/ap020128.html ] of the Taurus-Littrow valley in the Moon's Mare [ http://www.fourmilab.ch/earthview/lunarform/ maria.html ] Serenitatis. It was taken in 1972 from the Apollo 17 Command Module, America [ http://nssdc.gsfc.nasa.gov/nmc/tmp/ 1972-096A.html ], orbiting about 100 kilometers above the Moon's surface and covers an area about 1.1 kilometers wide. Using a web site [ http://www.boulder.swri.edu/~durda/Apollo/ landing_sites.html ] created by Dan Durda of Southwest Research Institute, armchair astronauts can explore orbital views of this and the 5 other Apollo [ http://www.hq.nasa.gov/office/pao/History/apollo.html ] lunar landing sites. |
|
Io: Moon Over Jupiter
| Title |
Io: Moon Over Jupiter |
| Explanation |
How big is the Jovian moon Io [ http://www.seds.org/nineplanets/ nineplanets/io.html ]? The most volcanic body [ http://volcano.und.nodak.edu/vwdocs/planet_volcano/ other_worlds.html ] in the Solar System, Io (usually pronounced "EYE-oh") is 3,600 kilometers in diameter, about the size of planet Earth's single large natural satellite [ http://antwrp.gsfc.nasa.gov/apod/ap010127.html ]. Gliding past Jupiter [ http://www.jpl.nasa.gov/jupiterflyby/ ] at the turn of the millennium, the Cassini spacecraft captured this awe inspiring view [ http://ciclops.lpl.arizona.edu/ciclops/images_jupiter.html ] of active Io [ http://www.jpl.nasa.gov/galileo/moons/io.html ] with the largest [ http://www.seds.org/nineplanets/nineplanets/ datamax.html ] gas giant as a backdrop, offering a stunning demonstration of the ruling planet's relative size [ http://nssdc.gsfc.nasa.gov/planetary/factsheet/ jupiterfact.html ]. Although in the picture Io [ http://photojournal.jpl.nasa.gov/cgi-bin/ PIAGenCatalogPage.pl?PIA02879 ] appears to be located just in front of the swirling Jovian clouds, Io hurtles around its orbit once every 42 hours at a distance of 420,000 kilometers or so from the center of Jupiter [ http://nssdc.gsfc.nasa.gov/planetary/factsheet/ joviansatfact.html ]. That puts it nearly 350,000 kilometers above Jupiter's cloud tops [ http://antwrp.gsfc.nasa.gov/apod/ap010215.html ], roughly equivalent to the distance between Earth and Moon [ http://antwrp.gsfc.nasa.gov/apod/ap980904.html ]. The Cassini spacecraft [ http://saturn.jpl.nasa.gov/cassini/english/spacecraft/ ] itself was about 10 million kilometers from Jupiter when recording the image data. |
|
Footprints on Another World
| Title |
Footprints on Another World |
| Explanation |
On July 20th, 1969 [ http://www.hq.nasa.gov/office/pao/History/ap11ann/ introduction.htm ], humans first set foot on the Moon [ http://seds.lpl.arizona.edu/nineplanets/nineplanets/ luna.html ]. Taken from a window of their Apollo 11 lunar module, the Eagle, this picture shows the footprints in the powdery lunar soil [ http://antwrp.gsfc.nasa.gov/apod/ap011110.html ] made by astronauts Neil Armstrong [ http://www.hq.nasa.gov/office/pao/History/ap11ann/ kippsphotos/5528.jpg ] and Buzz Aldrin [ http://www.hq.nasa.gov/office/pao/History/ap11ann/ kippsphotos/5390.jpg ]. It has been estimated that one billion people on planet Earth watched [ http://guinan.gsfc.nasa.gov/docs/heasarc/videos/ historical.html ] Armstrong step from the lander onto the surface of another world [ http://www.hq.nasa.gov/alsj/ ], making this live transmission one of the highest rated television shows ever. In the foreground at right, a rocket nozzle on the side of the Eagle is seen in silhouette, while beyond an unfurled United States [ http://aesp.nasa.okstate.edu/fieldguide/ ] flag is the television camera, remounted on a stand to better view the landing area. The Apollo missions [ http://www.ksc.nasa.gov/history/apollo/apollo.html ] to the Moon have been described as the result of the greatest technological mobilization in history [ http://www.hq.nasa.gov/office/pao/History/ ]. |
|
Asteroid 2002 NY40
| Title |
Asteroid 2002 NY40 |
| Explanation |
Asteroid 2002 NY40 [ http://science.nasa.gov/headlines/y2002/ 30jul_ny40.htm ] will fly by planet Earth early in the morning August 18 Universal Time (late in the evening August 17 Eastern Daylight Time). Approaching to within [ http://neo.jpl.nasa.gov/ ] about 530,000 kilometers or 1.3 times the Earth-Moon distance 2002 NY40 [ http://neo.jpl.nasa.gov/cgi-bin/db?name=2002+NY40 ] will definitely not be close enough to pose any danger of collision. But it will be close enough and just bright enough for experienced skygazers to see this 800 meter wide space rock [ http://seds.lpl.arizona.edu/nineplanets/nineplanets/ asteroids.html ] in a small telescope or binoculars as it glides quickly through northern skies [ http://science.nasa.gov/headlines/y2002/images/ny40/ skymap_ut.gif ] past the bright star Vega. It will also be close enough to ping with radar [ http://echo.jpl.nasa.gov/ ], and asteroid hunters using the large Arecibo radio telescope [ http://antwrp.gsfc.nasa.gov/apod/ap981129.html ] in Puerto Rico expect to determine the three dimensional outline of 2002 NY40. Similar investigations of other near Earth [ http://antwrp.gsfc.nasa.gov/apod/ap970120.html ] asteroids have revealed some surprising shapes [ http://antwrp.gsfc.nasa.gov/apod/ap000510.html ]. In this five minute time exposure, recorded at Cerro Tololo [ http://www.ctio.noao.edu/ ] Inter-American Observatory on August 14, 2002 NY40 shows itself as a long smudge as it moves against a background of faint stars in the constellation Aquarius [ http://www.windows.ucar.edu/tour/link=/the_universe/ Constellations/aquarius.html ]. |
|
Mercury's Caloris Basin
| Title |
Mercury's Caloris Basin |
| Explanation |
Mercury [ http://antwrp.gsfc.nasa.gov/apod/ap950814.html ], the closest planet to the Sun [ http://antwrp.gsfc.nasa.gov/apod/ap950813.html ], has a surface with so many craters it resembles the Earth [ http://antwrp.gsfc.nasa.gov/apod/ap950622.html ]'s Moon [ http://antwrp.gsfc.nasa.gov/apod/ap950707.html ]. The largest surface feature on Mercury [ http://seds.lpl.arizona.edu/nineplanets/nineplanets/mercury.html ] is the Caloris Basin, which resulted from a collision with an asteroid [ http://antwrp.gsfc.nasa.gov/apod/ap951020.html ]. The basin, which is more that 1000 kilometers across, is visible as the large circular feature at the bottom of the above photograph. Similar features, such as the Mare Orientale [ http://antwrp.gsfc.nasa.gov/apod/ap960112.html ], are seen on the Moon. The Caloris Basin gets very hot because it is near the "sub-solar point" - the point on Mercury [ http://bang.lanl.gov/solarsys/mercury.htm ]'s surface that is directly under the Sun [ http://antwrp.gsfc.nasa.gov/apod/ap951004.html ] when Mercury [ http://stardust.jpl.nasa.gov/planets/welcome/mercury.htm ] is closest to the Sun [ http://antwrp.gsfc.nasa.gov/apod/ap951024.html ]. |
|
Stereo Saturn
| Title |
Stereo Saturn |
| Explanation |
Get out your red/blue glasses [ http://mpfwww.jpl.nasa.gov/MPF/mpf/glasses.html ] and launch [ http://beacon.jpl.nasa.gov/exhibits/voyager/ default.html ] yourself into this stereo [ http://cass.jsc.nasa.gov/research/stereo_atlas/ SS3D.HTM ] picture of Saturn! The picture is actually composed from two images recorded weeks apart by the Voyager 2 spacecraft [ http://nssdc.gsfc.nasa.gov/database/ MasterCatalog?sc=1977-076A ] during its visit to [ http://sse.jpl.nasa.gov/missions/sat_missns/ sat-voy2.html ] the Saturnian System in August of 1981. Traveling at about 35,000 miles per hour, the spacecraft's changing viewpoint from one image to the next produced this exaggerated but pleasing stereo effect [ http://antwrp.gsfc.nasa.gov/apod/ap970404.html ]. Saturn is the second largest planet [ http://seds.lpl.arizona.edu/nineplanets/nineplanets/ saturn.html ] in the Solar System, after Jupiter. Its spectacular ring system [ http://ringmaster.arc.nasa.gov/saturn/saturn.html ] is so wide that it would span the space between the Earth and Moon. Although they look solid here, Saturn's [ http://antwrp.gsfc.nasa.gov/apod/ap000129.html ] rings consist of individually orbiting bits of ice and rock ranging in size from grains of sand to barn-sized boulders. |
|
Uranus' Largest Moon: Titani
…
| Title |
Uranus' Largest Moon: Titania |
| Explanation |
Titania's tortured terrain is a mix of valleys and craters. NASA's interplanetary robot spacecraft Voyager [ http://spacelink.msfc.nasa.gov/NASA.Projects/Planetary.Probes/Voyager/Mission.Summary ] 2 passed this moon of Uranus [ http://antwrp.gsfc.nasa.gov/apod/ap950816.html ] in 1986 and took the above photograph. The photograph was then transmitted back to earth by radio [ http://www.science.uwaterloo.ca/physics/p13news/number_2/maxnew-2.html ]. The valleys of Titania [ http://bang.lanl.gov/solarsys/titania.htm ] resemble those on Ariel [ http://antwrp.gsfc.nasa.gov/apod/ap960303.html ] indicate that Titania underwent some unknown tumultuous resurfacing event in its distant past. Although Titania [ http://seds.lpl.arizona.edu/nineplanets/nineplanets/titania.html ] is Uranus' largest moon, it is still much smaller than Triton [ http://antwrp.gsfc.nasa.gov/apod/ap950805.html ] - the largest moon of Uranus' sister planet Neptune [ http://antwrp.gsfc.nasa.gov/apod/ap950817.html ]. Titania is essentially a large dirty iceball that orbits Uranus - it is composed of about half water-ice and half rock. Titania was discovered by William Hershel [ http://www.dsi.unimi.it/Users/Students/amoroso/sun/fortunes/life-e.html ] in 1787. |
|
Voyager Views Titan's Haze
| Title |
Voyager Views Titan's Haze |
| Explanation |
Launched in 1977, 25 years ago [ http://voyager.jpl.nasa.gov/science/ planetary.html ] today, the Voyager 1 [ http://nssdc.gsfc.nasa.gov/database/ MasterCatalog?sc=1977-084A ] spacecraft's historic tour of the outer Solar System took it past Saturn in late 1980. On November 12, 1980, Voyager 1 recorded this view [ http://photojournal.jpl.nasa.gov/cgi-bin/ PIAGenCatalogPage.pl?PIA01533 ] looking across the edge of Titan [ http://seds.lpl.arizona.edu/nineplanets/ nineplanets/titan.html ], Saturn's largest moon, from a distance of about 22,000 kilometers. Seen in false color, the moon's [ http://antwrp.gsfc.nasa.gov/apod/ap990207.html ] hazy atmosphere [ http://photojournal.jpl.nasa.gov/cgi-bin/ PIAGenCatalogPage.pl?PIA02238 ] appears orange with further layers of blue haze suspended above. Titan's mostly nitrogen atmosphere, denser than planet Earth's, also contains methane [ http://antwrp.gsfc.nasa.gov/apod/ap020212.html ] and is thought to be laced with more complex hydrogen and carbon compounds. The composition is likened [ http://www.lifeinuniverse.org/noflash/ Titanstate-06-02-01-01.html ] to Earth's atmosphere before life began. Spotted by Voyager [ http://voyager.jpl.nasa.gov/science/ saturn_titan.html ], the detached layers of haze hundreds of kilometers above the surface, along with details of Titan's atmospheric chemistry, have intrigued earth-bound researchers [ http://amesnews.arc.nasa.gov/releases/2002/ 02_93AR.html ] who have recently proposed a model that links seasonal variations in the haze, winds, and sunlight. Their model accounts for [ http://skyandtelescope.com/news/current/ article_716_1.asp ] the early Voyager observations as well as subsequent studies [ http://www.lpl.arizona.edu/~lemmon/titan/ ]. Further tests of the model are anticipated when the Huygens probe [ http://saturn.jpl.nasa.gov/cassini/english/spacecraft/ probe.shtml ], carried by the saturn-bound [ http://antwrp.gsfc.nasa.gov/apod/ap971016.html ] Cassini spacecraft, enters Titan's atmosphere in 2005. |
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The McMath-Pierce Solar Obse
…
| Title |
The McMath-Pierce Solar Observatory |
| Explanation |
This odd-looking structure silhouetted in the foreground houses the three largest solar telescopes in the world. Located in Kitt Peak [ http://argo.tuc.noao.edu/nsokp/nsokp.html ], Arizona, the largest telescope inside the McMath-Pierce Facility [ http://argo.tuc.noao.edu/nsokp/mp.html ] is 1.6-meters in diameter and contains only mirrors. The telescope contains no windows or lenses because focusing bright sunlight would overheat them. Visible in the background of this sunrise photo are the Moon [ http://antwrp.gsfc.nasa.gov/apod/ap960222.html ] and Venus [ http://antwrp.gsfc.nasa.gov/apod/ap950822.html ]. The telescopes are used in many research projects including determining the Sun's structure [ http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1993BAAS%2E%2E183%2E5902U&db_key=AST ], researching the cause of the solar corona [ http://antwrp.gsfc.nasa.gov/apod/ap951024.html ], monitoring Sun-spots [ http://www.hao.ucar.edu/public/slides/slide3.html ] and solar flares [ http://antwrp.gsfc.nasa.gov/apod/ap950813.html ], and observing bright planets and comets near the Sun [ http://www.dsi.unimi.it/Users/Students/amoroso/sun/list-e.html ]. The telescopes even help monitor the Earth's atmospheric content of ozone [ http://www.cis.ohio-state.edu/hypertext/faq/usenet/ozone-depletion/top.html ] and CFCs [ http://duckworth.rh.imsa.edu/~yensid/chem/ozonedepletion.html ]! |
|
Cassini Approaches Saturn
| Title |
Cassini Approaches Saturn |
| Explanation |
Cassini, a robot spacecraft [ http://saturn.jpl.nasa.gov/spacecraft/index.cfm ] launched [ http://antwrp.gsfc.nasa.gov/apod/ap971016.html ] in 1997 by NASA [ http://www.nasa.gov/ ], is close enough now to resolve many rings [ http://antwrp.gsfc.nasa.gov/apod/ap020215.html ] and moons [ http://mars.sgi.com/worlds/CyberMarz/Saturn/HTML/saturnMoons.html ] of its destination planet: Saturn [ http://www.nineplanets.org/saturn.html ]. The spacecraft has closed to about two Earth-Sun separations [ http://einstein.stcloudstate.edu/Dome/constellns/au.html ] from the ringed giant [ http://antwrp.gsfc.nasa.gov/apod/ap011223.html ]. Last month, Cassini [ http://saturn.jpl.nasa.gov/overview/index.cfm ] snapped several images during an engineering test. These images have been combined into the contrast-enhanced color composite pictured above [ http://photojournal.jpl.nasa.gov/catalog/PIA02884 ]. Saturn's rings and cloud-tops [ http://antwrp.gsfc.nasa.gov/apod/ap960317.html ] are visible on the far right, while Titan [ http://www.solarviews.com/eng/titan.htm ], its largest moon, is visible as the speck on the lower left. When arriving at Saturn in July 2004, the Cassini orbiter [ http://saturn.jpl.nasa.gov/overview/mission.cfm ] will begin to circle and study the Saturnian system. Several months later, a probe named Huygens [ http://saturn.jpl.nasa.gov/overview/huygens-probe.cfm ] will separate and attempt to land on the surface of Titan [ http://antwrp.gsfc.nasa.gov/apod/ap020905.html ]. |
|
Jupiter, Io and Shadow
| Title |
Jupiter, Io and Shadow |
| Explanation |
Pictured above [ http://photojournal.jpl.nasa.gov/cgi-bin/ PIAGenCatalogPage.pl?PIA02860 ] is the innermost of Jupiter's Galilean satellites [ http://www.jpl.nasa.gov/galileo/ganymede/ discovery.html ], Io, superposed in front of the gas giant planet. To the left of Io [ http://www.seds.org/nineplanets/nineplanets/io.html ] is a dark spot that is Io's own shadow. A solar eclipse [ http://antwrp.gsfc.nasa.gov/apod/ap021206.html ] would be seen from within the shadow spot on Jupiter. Viewed from [ http://space.jpl.nasa.gov ] planet Earth, similar shadows of Jupiter's large moons can often be seen crossing [ http://antwrp.gsfc.nasa.gov/apod/ap980202.html ] the giant planet's disk. But during the next several months, the Galilean moons can also be seen crossing in front of each other [ http://skyandtelescope.com/observing/objects/planets/ article_771_1.asp ] as, for a while, their orbits lie nearly edge-on when viewed [ http://space.jpl.nasa.gov/cgi-bin/wspace?tbody=105&vbody=3&month=12&day=20¢ury=20&decade=0&year=2&hour=21&minute=35&rfov=30&fovmul=-1&bfov=30 ] by earthbound observers. This true-color contrast-enhanced image was taken [ http://ciclops.lpl.arizona.edu/ciclops/images_jupiter.html ] two years ago by the robot spacecraft Cassini, as it passed Jupiter on its way [ http://antwrp.gsfc.nasa.gov/apod/ap021104.html ] to Saturn in 2004. |
|
A Year of Assessing Astronom
…
| Title |
A Year of Assessing Astronomical Hazards |
| Explanation |
Could an asteroid destroy civilization on Earth? Mountain-sized space rocks [ http://antwrp.gsfc.nasa.gov/apod/ap000417.html ] could potentially impact the Earth [ http://impact.arc.nasa.gov/ ] causing global effects, and perhaps even be mistaken for a nuclear blast of terrestrial origin. Such large impacts are rare but have happened before [ http://antwrp.gsfc.nasa.gov/apod/ap990711.html ]. Modern telescopes have therefore begun to scan the skies for signs of approaching celestial hazards [ http://antwrp.gsfc.nasa.gov/apod/ap020623.html ]. Over the past year, projects such as Spacewatch [ http://spacewatch.lpl.arizona.edu/ ] and Spaceguard [ http://spaceguard.ias.rm.cnr.it/SGF/ ] have continually discovered previously unknown asteroids [ http://www.nineplanets.org/asteroids.html ] that indeed pass near the Earth. Such projects are still rather modest, however. In June, 100-meter asteroid 2002 MN [ http://SkyandTelescope.com/news/current/article_641_1.asp ] was discovered only "after" it whizzed by [ http://antwrp.gsfc.nasa.gov/apod/ap020817.html ] the Earth, crossing even within the orbit of the Moon. This year brought much discussion in the astronomical community of expanding technology [ http://www.ifa.hawaii.edu/pan-starrs/neos.html ] to discover most large Near Earth Objects [ http://neo.jpl.nasa.gov/ ] and extend the time between discovery [ http://antwrp.gsfc.nasa.gov/apod/ap021009.html ] and impact for all potential astronomical hazards [ http://www.pbs.org/wgbh/nova/gamma/milkyway.html ]. Pictured above [ http://www.iaaa.org/exhibit/gall1.html#8 ] is an illustration of a busy planetary system [ http://antwrp.gsfc.nasa.gov/apod/ap020724.html ], showing the view of a planet ringed with space debris from a recently formed crater of an orbiting moon. |
|
Io Volcano Culann Patera
| Title |
Io Volcano Culann Patera |
| Explanation |
What causes the unusual colors surrounding Io's volcanoes? Io [ http://www.nineplanets.org/io.html], the innermost large moon [ http://www.jpl.nasa.gov/galileo/ganymede/discovery.html ] of Jupiter [ http://www.solarviews.com/eng/jupiter.htm ], is known to be the most tumultuous body [ http://antwrp.gsfc.nasa.gov/apod/ap010715.html ] in the Solar System [ http://www.nineplanets.org/overview.html ]. Approximately the size of Earth's Moon [ http://antwrp.gsfc.nasa.gov/apod/ap010218.html ], Io undergoes nearly continuous volcanic eruptions [ http://antwrp.gsfc.nasa.gov/apod/ap000606.html ] from an interior heated by gravitational tides [ http://burro.astr.cwru.edu/Academics/Astr221/Gravity/tides.html ] from Jupiter and Jupiter's other large moons. The robot spacecraft Galileo [ http://galileo.jpl.nasa.gov/mission/space-intro.html ] currently orbiting Jupiter has been monitoring the active volcano Culann Patera [ http://pirlwww.lpl.arizona.edu/missions/Galileo/releases/19May_i25culann.html ] over the past few years. The above images [ http://photojournal.jpl.nasa.gov/catalog/PIA03885 ] indicate that the volcano [ http://volcano.und.nodak.edu/volcanoes.html ] has produced not only red and black colored lava flows [ http://volcanoes.usgs.gov/Hazards/What/Lava/lavaflow.html ], but yellow sulfur [ http://pearl1.lanl.gov/periodic/elements/16.html ] patches from explosive plumes. Green colors may arise when these processes affect the same terrain. White patches may be caused, in part, by sulfur dioxide [ http://www.epa.gov/air/aqtrnd95/so2.html ] snow. As Galileo [ http://nssdc.gsfc.nasa.gov/planetary/galileo.html ] has fulfilled its mission objectives [ http://antwrp.gsfc.nasa.gov/apod/ap021218.html http://nssdc.gsfc.nasa.gov/planetary/galileo.html#objective ] and is running low on maneuvering fuel, NASA plans to crash [ http://astrobiology.arc.nasa.gov/news/expandnews.cfm?id=392 ] the spacecraft into Jupiter during 2003. |
|
Europa's Surface
| Title |
Europa's Surface |
| Explanation |
Voyager spacecraft [ http://nssdc.gsfc.nasa.gov/photo_gallery/photogallery-voyager.html ] images of Europa's surface [ http://seds.lpl.arizona.edu/nineplanets/nineplanets/europa.html ], like the one above, are suggestive of sea ice on Earth [ http://antwrp.gsfc.nasa.gov/apod/ap951118.html ]. The criss-crossing dark streaks may indeed be cracks in its ice-covered surface caused by Jupiter's tidal stresses accompanied by the freezing and expansion of an underlying layer of water [ http://antwrp.gsfc.nasa.gov/apod/ap960806.html ]. This tantalizing prospect of oceans of liquid water [ http://antwrp.gsfc.nasa.gov/apod/ap950905.html ] beneath its frozen surface has helped make the smallest of the Galilean [ http://galileo.imss.firenze.it/museo/4/index.html ] moon's of Jupiter a planned focus of the Galileo spacecraft's ongoing mission to explore the Jovian system. New Europa images and results [ http://newproducts.jpl.nasa.gov/galileo/index.html ] from the Galileo mission were released today revealing [ ftp://ftp.hq.nasa.gov/pub/pao/pressrel/1996/96-164.txt ] details which further suggest that Europa's icy surface was once - and may still be - supported on slush or liquid water. |
|
Europa: Oceans of Life?
| Title |
Europa: Oceans of Life? |
| Explanation |
Is there life beneath Europa's frozen surface? Some believe the oceans found there of carbon-enriched water are the best chance for life [ http://www.etext.org/Zines/Quanta/life.html ], outside the Earth [ http://ucmp1.berkeley.edu/alllife/threedomains.html ], in our Solar System [ http://antwrp.gsfc.nasa.gov/apod/ap950819.html ]. Europa [ http://seds.lpl.arizona.edu/nineplanets/nineplanets/europa.html ], the fourth largest moon of Jupiter [ http://antwrp.gsfc.nasa.gov/apod/ap950714.html ], was recently discovered [ http://www.stsci.edu/pubinfo/press-releases/95-12.txt ] to have a thin oxygen atmosphere by scientists using the Hubble Space Telescope [ http://antwrp.gsfc.nasa.gov/apod/ap950810.html ]. Although Earth's atmospheric [ http://www.aspire.cs.uah.edu/~jonesj/r.html ] abundance of oxygen is indicative of life [ http://www.gtri.gatech.edu/rh-win96/oxygen.htm ], astronomers speculate that Europa's oxygen arises purely from physical processes. But what an interesting coincidence! The above picture was taken by a Voyager spacecraft [ http://nssdc.gsfc.nasa.gov/photo_gallery/photogallery-voyager.html ] in 1979, but the spacecraft Galileo [ http://www.jpl.nasa.gov/galileo/index.html ] is currently circling Jupiter [ http://antwrp.gsfc.nasa.gov/apod/lib/jupiter.html ] and has been photographing [ http://www.jpl.nasa.gov/galileo/countdown/g1time.html ] Europa [ http://bang.lanl.gov/solarsys/europa.htm ]. The first of these pictures will be released two days from today. Will they show the unexpected? [ http://www.vsc.washington.edu/academic/499/Resources/europa.html ] |
|
Welcome to Planet Earth
| Title |
Welcome to Planet Earth |
| Explanation |
Welcome to Planet Earth [ http://antwrp.gsfc.nasa.gov/apod/lib/earth.html ], the third planet from a star [ http://antwrp.gsfc.nasa.gov/apod/lib/glossary.html#star ] named the Sun [ http://antwrp.gsfc.nasa.gov/htmltest/gifcity/interv.html ]. The Earth is shaped like a sphere [ http://octopus.gma.org/space1/nav_map.html ] and composed mostly of rock [ http://www.seismo.unr.edu/ftp/pub/louie/class/plate/composition.html ]. Over 70 percent of the Earth's surface [ http://brentw.ccit.arizona.edu/edp512/v2.html ] is water [ http://h2o.er.usgs.gov/public/watuse/wuqa.usage.html ]. The planet has a relatively thin atmosphere [ http://www.aspire.cs.uah.edu/~jonesj/r.html ] composed mostly of nitrogen [ http://web.cetlink.net/~yinon/n.html ] and oxygen [ http://www.gtri.gatech.edu/rh-win96/oxygen.htm ]. Earth has a single large Moon [ http://antwrp.gsfc.nasa.gov/apod/lib/moon.html ] which is about 1/4 of its diameter and, from the planet's surface, is seen to have almost exactly the same angular size as the Sun [ http://antwrp.gsfc.nasa.gov/apod/lib/sun.html ]. With its abundance of liquid water [ http://antwrp.gsfc.nasa.gov/apod/ap951118.html ], Earth supports a large variety of life forms [ http://www.arts.ucsb.edu/~nideffer/.virus/kates.html ], including potentially intelligent species such as dolphins [ http://www.polaris.net/~rblacks/dolphins.htm ] and humans [ http://antwrp.gsfc.nasa.gov/apod/ap960629.html ]. Please enjoy your stay on Planet Earth. |
|
When Moons and Shadows Dance
| Title |
When Moons and Shadows Dance |
| Explanation |
It's no wonder Jupiter is [ http://galileo.jpl.nasa.gov/jupiter/ jupiter.html ] a favorite target for [ http://www.lpl.arizona.edu/~rhill/alpo/jup.html ] even modest earthbound telescopes. The most massive planet in the solar system [ http://www.seds.org/nineplanets/ nineplanets/datamax.html ] with four of the largest moons also boasts the famous Great Red Spot [ http://csep10.phys.utk.edu/astr161/lect/jupiter/ redspot.html ], a giant hurricane-like storm system over three hundred years old. Recorded on December 15, 2002 between 7:19 and 8:40 UT, over a thousand digital images were processed and stacked to create this spectacular 21 frame animation of the Jovian system [ http://antwrp.gsfc.nasa.gov/apod/ap001118.html ]. South is up and as the Great Red Spot tracks across the face of Jupiter, innermost Galilean [ http://www.jpl.nasa.gov/galileo/ganymede/ discovery.html ] moon Io enters the scene at the far right. Io occults (passes in front of) the edge of the more sedately orbiting Ganymede with Io's shadow [ http://antwrp.gsfc.nasa.gov/apod/ap021207.html ] moving quickly across the gas giant's cloud tops, just below the Red Spot. While the moon Callisto is outside the field of view, its large, dark shadow is also visible crossing the Jovian disk at the upper left. Viewed from Earth, the orbits of the Galilean moons presently lie nearly edge-on, offering many chances to observe similar dances of Jupiter's moons [ http://skyandtelescope.com/observing/objects/planets/ article_771_1.asp ]. |
|
Farewell Jupiter
| Title |
Farewell Jupiter |
| Explanation |
Next stop: Saturn. The Cassini spacecraft [ http://saturn.jpl.nasa.gov/spacecraft/ ], launched from Earth [ http://antwrp.gsfc.nasa.gov/apod/ap971016.html ] in 1997, has now [ http://saturn.jpl.nasa.gov/operations/present-position.cfm ] swung past Jupiter [ http://www.jpl.nasa.gov/jupiterflyby/ ] and should arrive at Saturn [ http://www.nineplanets.org/saturn.html ] in the year 2004. Pictured to the left [ http://photojournal.jpl.nasa.gov/cgi-bin/PIAGenCatalogPage.pl?PIA03451 ] is a parting shot [ http://ciclops.lpl.arizona.edu/ciclops/images_jupiter.html ] from Cassini in 2001 January that would not have been possible from Earth: Jupiter showing a crescent phase [ http://antwrp.gsfc.nasa.gov/apod/ap010619.html ]. From the Earth and all points sunward of Jupiter [ http://www.nineplanets.org/jupiter.html ], the gas giant will always appear more fully lit than a crescent [ http://antwrp.gsfc.nasa.gov/apod/ap010218.html ]. Recent analysis of Jupiter images [ http://ciclops.lpl.arizona.edu/ciclops/images_jupiter.html ] taken from Cassini bolsters indications that clouds [ http://antwrp.gsfc.nasa.gov/apod/ap970920.html ] well up from below in the dark colored belts, not the light colored zones [ http://antwrp.gsfc.nasa.gov/apod/ap000429.html ], as believed previously. After arriving at Saturn, Cassini [ http://www-groups.dcs.st-andrews.ac.uk/~history/Mathematicians/Cassini.html ] will decelerate to orbit [ http://saturn.jpl.nasa.gov/operations/saturn-arrival.cfm ] the ringed world and send a probe [ http://saturn.jpl.nasa.gov/operations/huygens-mission.cfm ] to its enigmatic moon Titan [ http://antwrp.gsfc.nasa.gov/apod/ap000820.html ]. |
|
Southwest Mercury
| Title |
Southwest Mercury |
| Explanation |
The planet Mercury resembles a moon. Mercury [ http://seds.lpl.arizona.edu/nineplanets/nineplanets/mercury.html ]'s old surface is heavily cratered [ http://antwrp.gsfc.nasa.gov/apod/ap950924.html ] like many moons. Mercury [ http://bang.lanl.gov/solarsys/mercury.htm ] is larger than most moons but smaller than Jupiter [ http://antwrp.gsfc.nasa.gov/apod/ap951013.html ]'s moon Ganymede [ http://antwrp.gsfc.nasa.gov/apod/ap950904.html ] and Saturn [ http://antwrp.gsfc.nasa.gov/apod/ap960717.html ]'s moon Titan [ http://antwrp.gsfc.nasa.gov/apod/ap950923.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/ap960819.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/ap960912.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/ap951114.html ], stop again, and then set quickly over the other horizon. From Earth [ http://antwrp.gsfc.nasa.gov/apod/ap951118.html ], Mercury's proximity to the Sun [ http://antwrp.gsfc.nasa.gov/apod/ap960727.html ] cause it to be visible only for a short time [ http://www.maths.qmw.ac.uk/~lms/research/skyeye.html#planet ] just after sunset or just before sunrise. |
|
Eclipsed Moon and Stars
| Title |
Eclipsed Moon and Stars |
| Explanation |
Half-shadowed [ http://www.dustbunny.com/afk/howdo/luneclipse/ luneclipse.htm ] by the Earth, the Moon takes on [ http://www.windows.ucar.edu/tour/link=/mythology/planets/ Earth/moon.html ] a remarkable appearance against a field of stars in this intriguing telephoto picture recorded during a partial phase of last week's lunar eclipse [ http://aa.usno.navy.mil/data/docs/LunarEclipse.html ]. The picture is not a composite [ http://antwrp.gsfc.nasa.gov/apod/ap010906.html ], but it has been digitally enhanced to bring out features covering a large range in brightness. On the Moon itself [ http://seds.lpl.arizona.edu/nineplanets/nineplanets/ luna.html ], surface details are visible in both the bright uneclipsed portion in direct sunlight, and the very much dimmer copper-colored [ http://antwrp.gsfc.nasa.gov/apod/ap030521.html ], eclipsed region. Also much fainter than the Moon's sunlit [ http://www.lhl.lib.mo.us/pubserv/hos/moon/p1.htm ] surface, the background star field, along with the unusual lighting, seems to contribute to an eerie "3D" perception of the lunar orb. Canadian astrophotographer Jay Ouellet took the picture from l'Observatoire de la Decouverte in Val Belair, a suburb of Quebec City, where about 200 skygazers gathered to enjoy the celestial exposition [ http://www.spaceweather.com/eclipses/ gallery_15may03_page4.html ]. |
|
Mars Rising Behind Poodle Ro
…
| Title |
Mars Rising Behind Poodle Rock |
| Explanation |
Have you seen Mars lately? As Earth [ http://antwrp.gsfc.nasa.gov/apod/ap010204.html ] and Mars [ http://antwrp.gsfc.nasa.gov/apod/ap030728.html ] near their closest approach in nearly 60,000 years [ http://mars.jpl.nasa.gov/spotlight/marsClose01.html ] on August 27, the red planet [ http://www.nineplanets.org/mars.html ] has begun to appear dramatically bright and show interesting details [ http://antwrp.gsfc.nasa.gov/apod/ap030724.html ] through telescopes and binoculars. Although not yet visible at sunset, Mars [ http://www.tnni.net/~dustymars/2003_MARS.htm ] can be seen rising [ http://skyandtelescope.com/observing/ataglance/article_110_1.asp ] increasingly earlier in the evening. Once above the horizon, Mars is easy to spot [ http://skyandtelescope.com/observing/objects/planets/article_985_1.asp ], as it sports a distinct orange-red hue and it is the brightest object in the sky after the Sun [ http://antwrp.gsfc.nasa.gov/apod/sun.html ], the nearby Moon [ http://antwrp.gsfc.nasa.gov/apod/moon.html ], and Venus [ http://antwrp.gsfc.nasa.gov/apod/venus.html ]. After Earth overtakes Mars [ http://www.earthsky.com/2003/es030728.html ] in their respective solar orbits, Mars will be visible [ http://www.space.com/spacewatch/mars_preview_021108.html ] right from sunset, although its historic brightness will then begin to fade [ http://www.lpl.arizona.edu/~rhill/alpo/marstuff/ephems/ephem2003.html ]. Pictured above [ http://www.astropics.com/mars/index.htm ], Mars was captured rising in the south east next to Poodle Rock in Valley of Fire State Park [ http://parks.nv.gov/vf.htm ], Nevada [ http://quickfacts.census.gov/qfd/index.html ], USA [ http://www.cia.gov/cia/publications/factbook/geos/us.html ]. |
|
The E Nebula in Aquila
| Title |
The E Nebula in Aquila |
| Explanation |
Several unusual strands of darkness [ http://antwrp.gsfc.nasa.gov/apod/ap020526.html ] are prominent toward the constellation of Aquila [ http://chandra.harvard.edu/photo/constellations/aquila.html ]. This particular dark nebula [ http://zebu.uoregon.edu/~js/glossary/dark_nebula.html ] is known as the E Nebula, for its evocative shape, or B142 and B143, for its position(s) on a list of such nebula compiled by Barnard [ http://astro.uchicago.edu/yerkes/virtualmuseum/Barnard.html ]. The E Nebula [ http://www.eastbayastro.org/articles/lore/aquila.htm ] spans roughly the angle of a full Moon [ http://antwrp.gsfc.nasa.gov/apod/ap030810.html ] and lies about 2000 light years [ http://starchild.gsfc.nasa.gov/docs/StarChild/questions/question19.html ] distant. The nebula [ http://www.abmedia.com/astro/current/b142-b143-fs102.html ] can be seen with binoculars and is particularly visible during the summer months in Earth's northern hemisphere. Other names for dark nebula [ http://antwrp.gsfc.nasa.gov/apod/dark_nebulae.html ] include absorption nebula [ http://www.glyphweb.com/esky/concepts/absorptionnebula.html ], as they efficiently absorb visible light emitted behind them, and molecular clouds [ http://etacha.as.arizona.edu/~eem/ttau/gmc.html ], as they frequently attain temperatures low enough so that several different types of stable molecules [ http://www.chem.ox.ac.uk/mom/ ] can exist. The low temperatures of these interstellar clouds [ http://antwrp.gsfc.nasa.gov/apod/ap020210.html ] facilitate the formation of dense knots [ http://antwrp.gsfc.nasa.gov/apod/ap011125.html ] of gas that may then collapse into bright stars. |
|
Galileo's Europa
| Title |
Galileo's Europa |
| Explanation |
Launched in 1989 and looping through the jovian system since late 1995, the voyage of NASA's Galileo spacecraft [ http://www.jpl.nasa.gov/galileo/mission_end.html ] will soon come to an end. The spacecraft has been targeted to plunge [ http://www.jpl.nasa.gov/galileo/news/release/ press030917.html ] directly into Jupiter this Sunday [ http://www.jpl.nasa.gov/galileo/countdown/ ], September 21st, at about 30 miles per second. Its components will be vaporized in the gas giant's outer atmosphere. While Galileo's long voyage of exploration has resulted in a spectacular scientific legacy [ http://galileo.jpl.nasa.gov/images/topTen01.html ], the spacecraft's ultimate fate is related to perhaps its most tantalizing discovery [ http://whyfiles.org/060moons/europa.html ] -- strong evidence for a liquid ocean [ http://www.jpl.nasa.gov/galileo/news8.html ] beneath the frozen surface of Jupiter's moon Europa [ http://www.jpl.nasa.gov/galileo/moons/europa.html ]. Galileo is now almost completely out of fuel for maneuvers, so this intentional collision with Jupiter will prevent any unintentional future collision with Europa and the possibility of contaminating the jovian moon with microbes from Earth hardy enough to survive [ http://science.nasa.gov/newhome/headlines/ ast01sep98_1.htm ] in interplanetary space. Color image data [ http://photojournal.jpl.nasa.gov/catalog/PIA02590 ] from the Galileo mission recorded between 1995 and 1998 was used to create this depiction of Europa's cracked and icy surface. The inset [ http://photojournal.jpl.nasa.gov/catalog/PIA02099 ] shows dark reddish, disrupted regions dubbed Thera and Thrace. |
|
Saturn by Three
| Title |
Saturn by Three |
| Explanation |
These three views of Saturn [ http://hubblesite.org/newscenter/archive/2003/23/image/a ] were recorded by the Hubble Space Telescope on March 7th of this year, as the southern hemisphere of the solar system's most gorgeous planet reached its maximum 27 degree tilt toward Earth [ http://antwrp.gsfc.nasa.gov/apod/ap030405.html ]. The images used to construct [ http://hubblesite.org/newscenter/archive/2003/23/ fastfacts ] the false-color pictures were made through a combination of filters covering [ http://hubblesite.org/sci.d.tech/behind_the_pictures/ meaning_of_color/hubble.shtml ] the electromagnetic spectrum from ultraviolet (top), to visible (middle) and infrared (bottom) wavelengths highlighting different features [ http://www.aas.org/publications/baas/v35n4/dps2003/ 22.htm ] in the Saturnian atmospheric bands and rings. Well known for its bright ring [ http://antwrp.gsfc.nasa.gov/apod/ap020215.html ] system and large, mysterious moon Titan [ http://antwrp.gsfc.nasa.gov/apod/ap020905.html ], gas giant Saturn is [ http://nssdc.gsfc.nasa.gov/planetary/factsheet/ saturnfact.html ] also a planet with a dynamic atmosphere and high-speed winds. In fact, in the 1980s, Voyager spacecraft measured [ http://voyager.jpl.nasa.gov/science/saturn.html ] equatorial winds of over 1,000 miles per hour. Giant storm systems [ http://antwrp.gsfc.nasa.gov/apod/ap030916.html ], comparable in size to planet Earth itself, have been seen erupting in Saturn's [ http://hubblesite.org/newscenter/archive/1994/53/ image/a ] cloud tops. |
|
Saturn's Rings Seen Sideways
| Title |
Saturn's Rings Seen Sideways |
| Explanation |
Saturn's rings [ http://antwrp.gsfc.nasa.gov/apod/ap950730.html ] are actually very thin. This picture [ http://www.stsci.edu/pubinfo/PR/96/16/A.html ] from the Hubble Space Telescope [ http://antwrp.gsfc.nasa.gov/apod/ap950810.html ] was taken on August 6, 1995 when the rings lined up sideways as seen from Earth [ http://antwrp.gsfc.nasa.gov/apod/ap970130.html ]. Saturn [ http://antwrp.gsfc.nasa.gov/apod/lib/saturn.html ]'s largest moon Titan [ http://antwrp.gsfc.nasa.gov/apod/ap950923.html ] is seen on the left, and Titan's shadow can be seen on Saturn's cloud tops [ http://antwrp.gsfc.nasa.gov/apod/ap960317.html ]! Titan itself looks a brownish color because of its thick atmosphere. Four other moon's of Saturn can be seen just above the ring plane, which are, from left to right: Mimas [ http://antwrp.gsfc.nasa.gov/apod/ap950924.html ], Tethys [ http://antwrp.gsfc.nasa.gov/apod/ap951124.html ], Janus [ http://seds.lpl.arizona.edu/nineplanets/nineplanets/janus.html ], and Enceladus [ http://antwrp.gsfc.nasa.gov/apod/ap951125.html ]. If you look carefully, you will note that the dark band across the planet is actually the " shadow " of the rings, and is slightly displaced from the real rings - which are best seen away from the planet. Saturn's rings [ http://newproducts.jpl.nasa.gov/saturn/back.html ] are not solid - they are composed of ice chunks which range in size from a grain of sand to a house. |
|
Jupiter And Family
| Title |
Jupiter And Family |
| Explanation |
This composite image [ http://galileo.ivv.nasa.gov/ganymede/052997.html ] features classic portraits of members of one of the Solar System's [ http://antwrp.gsfc.nasa.gov/apod/ap961214.html ] most prominent families - Jupiter [ http://antwrp.gsfc.nasa.gov/apod/ap970920.html ] and its four large "Galilean" [ http://antwrp.gsfc.nasa.gov/apod/ap960830.html ] moons. Starting from the top the moons are Io [ http://antwrp.gsfc.nasa.gov/apod/ap970321.html ], Europa [ http://antwrp.gsfc.nasa.gov/apod/ap970117.html ], Ganymede [ http://antwrp.gsfc.nasa.gov/apod/ap961107.html ], and Callisto [ http://antwrp.gsfc.nasa.gov/apod/ap961209.html ]. The top-to-bottom order is also the order of increasing distance from Jupiter. These are big moons indeed which attend the largest planet [ http://seds.lpl.arizona.edu/nineplanets/nineplanets/jupiter.html ]. The smallest of the lot, Europa, is the size of Earth's moon [ http://antwrp.gsfc.nasa.gov/apod/ap970924.html ] while Ganymede is the largest moon in the Solar System. In fact, Ganymede with a diameter of 3,100 miles, is larger than the planets Mercury [ http://antwrp.gsfc.nasa.gov/apod/ap961217.html ] and Pluto [ http://antwrp.gsfc.nasa.gov/apod/ap960311.html ]. The swirling Great Red Spot [ http://antwrp.gsfc.nasa.gov/apod/ap960827.html ] appears at the edge of Jupiter. A hurricane-like storm system that has persisted for over 300 years, two to three earths could fit inside it. Battered Callisto's [ http://antwrp.gsfc.nasa.gov/apod/ap950906.html ] image was recorded during the 1979 flyby of Voyager [ http://antwrp.gsfc.nasa.gov/apod/ap960629.html ]. The other portraits were taken by the Galileo spacecraft [ http://galileo.ivv.nasa.gov/spacecraft.html ] which began exploring the Jovian system in 1995. |
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