|
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Enceladus
This artist's rendering show
…
3/28/96
| Date |
3/28/96 |
| Description |
This artist's rendering shows the notable bright surface of icy Enceladus. In the foreground, an ice geyser can be seen projecting a jet of vapor into space. Enceladus is considered by some as the source of the E ring (which can be very faintly seen along Saturn's equatorial plane), icy geysers may be responsible for sustaining the E ring's supply of micrometer-sized particles. Cassini is a joint mission of NASA, the European Space Agency and the Italian Space Agency. The mission is scheduled for launch in October 1997 and will reach Saturn in July 2004. [Digital composition for NASA-JPL was created by Dave Seal of JPL.] |
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Tethys
One of the most exciting fea
…
3/28/96
| Date |
3/28/96 |
| Description |
One of the most exciting features of Tethys (and of the whole Saturnian system as well) is Ithaca Chasma, a huge trench which extends from near the north pole down almost all the way to the south pole. It's average width is 100 kilometers (60 miles) and is 4-5 kilometers (2-3 miles) deep. This artist's rendering is drawn from the lip of the large chasm looking into it, with Saturn in the background. By Cassini is a joint mission of NASA, the European Space Agency and the Italian Space Agency. The mission is scheduled for launch in October 1997 and will reach Saturn in July 2004. [Digital composition for NASA-JPL was created by Dave Seal of JPL.] |
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Titan w/ Huygens probe
This narrow angle field-of-v
…
3/28/96
| Date |
3/28/96 |
| Description |
This narrow angle field-of-view artist's rendering shows Titan's surface with Saturn dimly in the background through Titan's thick atmosphere of methane, ethane and (mostly) nitrogen. The Cassini spacecraft flys over the surface with its High Gain Antenna pointed at the Huygens probe as it reaches the surface. Thin methane clouds dot the horizon, and a narrow methane spring or "methanefall" flows from the cliff at left and drifts mostly into vapor. Smooth ice features rise out of the methane/ethane lake, and crater walls can be seen far in the distance. Cassini is a joint mission of NASA, the European Space Agency and the Italian Space Agency. The mission is scheduled for launch in October 1997 and will reach Saturn in July 2004. [Digital composition for NASA-JPL was created by Dave Seal of JPL.] |
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Installing Cassini's Thermal
…
Technicians install the gold
…
| Description |
Technicians install the gold-colored thermal blankets for NASA's Cassini spacecraft, which will be launched on a mission to the planet Saturn on Oct. 6, 1997. |
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Moons of the Solar System
| title |
Moons of the Solar System |
| description |
All the planetary moons in our solar system are shown here at their correct relative size and true color. Their diversity of size and appearance is testament to the unique and fascinating geologic history that each of these bodies has undergone. Two of the moons are larger than the planet Mercury, and eight of them are larger than Pluto. Earth's Moon is the fifth largest of the set, with a diameter of 3476 kilometers (2160 miles). Most of the moons are thought to have formed from a disk of debris left over from formation of the planet they orbit. However Triton, Neptune's largest moon, and several of the smallest moons, including the moons of Mars, are thought to be captured planetesimals that formed elsewhere in the solar system. Earth's Moon is thought to have formed from the debris ejected from a roughly Mars-sized object colliding with the early Earth, perhaps a unique event in the history of the solar system. The moons are organized on the diagram by the planet they orbit (top to bottom with increasing distance from the Sun) and their position relative to the planet (left to right with increasing distance from the planet). Below is a listing of the names of all the moons and the planets they orbit. Most moons are named for mythological characters associated with the character the planet is named for. While most of the planets are named for Roman characters (with the exceptions of Pluto and Uranus), most of the moon have names from Greek mythology. For example, Phobos and Deimos are the sons of Ares, the Greek version of Mars. Jupiter?s moons are all named for lovers and other close associates of Zeus (Jupiter). Saturn?s moons are named for Titans, the race that included Cronos (Saturn), Zeus? father. Neptune?s moons are named for mythological characters associated with water, and Charon was the ferryman of the dead who brought people to Pluto?s realm. By tradition, the discoverer of a moon gets to name it (now subject to approval by the International Astronomical Union). The son of the discoverer of the first two moons of Uranus (Sir William Herschel) decided to name Uranus? moons not for mythological characters, but instead for the king and queen of fairies in Shakespear?s A Midsummer Night?s Dream . This began a tradition whereby all uranian satellites are named for fairy characters in English drama. To read more about the names of the planets and their satellites, go to the U.S. Geological Survey?s nomenclature guide at http://wwwflag.wr.usgs.gov/USGSFlag/Space/nomen/append7.html . *Earth* Moon *Mars * Phobos, Deimos *Jupiter* Metis, Adrastea, Amalthea, Thebe, Io, Europa, Ganymede, Callisto, Leda, Himalia, Lysithea, Elara, Ananke, Carme, Pasiphae, Sinope *Saturn * Pan, Atlas, Prometheus, Pandora, Epimetheus, Janus, Mimas, Enceladus, Tethys, Calypso, Telesto, Dione, Helene, Rhea, Titan, Hyperion, Iapetus, Phoebe *Uranus * Cordelia, Ophelia, Bianca, Cressida, Desdemona, Juliet, Portia, Rosalind, Belinda, Puck, Miranda,, Ariel, Umbriel, Titania, Oberon *Neptune* Naiad, Thalassa, Despina, Galatea, Larissa, Proteus, Triton, Nereid *Pluto * Charon *Image Credit*: Image processing by Tim Parker (Jet Propulsion Laboratory) and Paul Schenk and Robert Herrick (Lunar and Planetary Institute), based on NASA images. |
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Enceladus Near Saturn
| Title |
Enceladus Near Saturn |
| Explanation |
Some images of Saturn appear surreal. Earlier this year, the robot spacecraft Cassini [ http://saturn.jpl.nasa.gov/spacecraft/index.cfm ] now orbiting Saturn took this surreal image [ http://antwrp.gsfc.nasa.gov/apod/ap030616.html ] of the gas giant Saturn [ http://en.wikipedia.org/wiki/Saturn ], its majestic rings [ http://pds-rings.seti.org/saturn/ ], and its enigmatic world Enceladus [ http://antwrp.gsfc.nasa.gov/apod/ap050906.html ] all in one frame. Enceladus, recently found to emit jets [ http://antwrp.gsfc.nasa.gov/apod/ap051205.html ] of ice from possible underground seas [ http://antwrp.gsfc.nasa.gov/apod/ap060310.html ], appears white as its surface is covered with relatively clean water-ice. Below Enceladus [ http://en.wikipedia.org/wiki/Enceladus_%28moon%29 ] are the rings of Saturn, seen nearly edge on [ http://antwrp.gsfc.nasa.gov/apod/ap051219.html ]. Compared to Enceladus, Saturn's rings show their comparatively high density of dirt with their golden-brown color in this natural color image [ http://photojournal.jpl.nasa.gov/catalog/PIA08128 ]. The planet Saturn, in the background, appears relatively featureless [ http://antwrp.gsfc.nasa.gov/apod/ap041102.html ] with the exception of thin ring shadows visible on the upper left. The terminator [ http://en.wikipedia.org/wiki/Terminator_%28solar%29 ] between night and day is seen vertically across the face of this distant world. |
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Natural Saturn On The Cassin
…
| Title |
Natural Saturn On The Cassini Cruise |
| Explanation |
What could you see approaching Saturn [ http://www.jpl.nasa.gov/cassini/Kids/stories/ ] aboard an interplanetary cruise [ http://www.jpl.nasa.gov:80/cassini/Mission/cruise.html ] ship? Your view would likely resemble this subtly shaded image [ http://oposite.stsci.edu/pubinfo/pr/1998/28/b.html ] of the gorgeous ringed gas giant. Processed by the Hubble Heritage project [ http://heritage.stsci.edu/ ], the picture intentionally avoids overemphasizing color contrasts and presents a natural looking Saturn [ http://heritage.stsci.edu/ public/Oct22/saturn/saturntable.html#caption ] with cloud bands, storms [ http://antwrp.gsfc.nasa.gov/apod/ap951018.html ], nearly edge-on rings [ http://antwrp.gsfc.nasa.gov/apod/ap981018.html ], and the small round shadow of the moon Enceladus near the center of the planet's disk. Of course, seats were not available on the only ship currently enroute [ http://www.jpl.nasa.gov/cassini/ ] - the Cassini spacecraft, launched in 1997 [ http://antwrp.gsfc.nasa.gov/apod/ap971016.html ] and scheduled to arrive at Saturn [ http://www.jpl.nasa.gov/cassini/today/ ] in the year 2004. After an extended cruise to a world 1,400 million kilometers from the Sun [ http://antwrp.gsfc.nasa.gov/apod/ap960727.html ], Cassini will tour the Saturnian system [ http://www.hawastsoc.org/solar/eng/saturn.htm ], conducting a remote, robotic exploration with software and instruments designed by [ http://www.jpl.nasa.gov/cassini/Partners/ ] denizens of planet Earth. But where is Cassini now [ http://www.jpl.nasa.gov/cassini/today/ ]? Still about 980 million kilometers from Saturn, last Sunday the spacecraft flew by asteroid 2685 Masursky [ http://www.jpl.nasa.gov/cassini/MoreInfo/ sigevents/sigevent000128.html ]. |
|
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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Southwest Mercury
| Title |
Southwest Mercury |
| Explanation |
The planet Mercury resembles a moon. Mercury [ http://www.seds.org/nineplanets/nineplanets/mercury.html ]'s old surface is heavily cratered [ http://liftoff.msfc.nasa.gov/Academy/SPACE/SolarSystem/Meteors/Craters.html ] like many moons. Mercury [ http://www.solarviews.com/eng/mercury.htm ] is larger than most moons but smaller than Jupiter [ http://antwrp.gsfc.nasa.gov/apod/ap990806.html ]'s moon Ganymede [ http://antwrp.gsfc.nasa.gov/apod/ap990304.html ] and Saturn [ http://antwrp.gsfc.nasa.gov/apod/ap960717.html ]'s moon Titan [ http://antwrp.gsfc.nasa.gov/apod/ap990207.html ]. Mercury is much denser and more massive than any moon, though, because it is made mostly of iron. In fact, the Earth [ http://antwrp.gsfc.nasa.gov/apod/ap990131.html ] is the only planet more dense. A visitor to Mercury's surface [ http://antwrp.gsfc.nasa.gov/apod/ap960121.html ] would see some strange sights. Because Mercury [ http://www.oulu.fi/~spaceweb/textbook/mercury.html ] rotates exactly three times every two orbits around the Sun [ http://antwrp.gsfc.nasa.gov/apod/ap951004.html ], and because Mercury [ http://nssdc.gsfc.nasa.gov/photo_gallery/photogallery-mercury.html ]'s orbit is so elliptical, a visitor to Mercury [ http://antwrp.gsfc.nasa.gov/apod/ap990102.html ] might see the Sun [ http://antwrp.gsfc.nasa.gov/htmltest/gifcity/interv.html ] rise, stop in the sky, go back toward the rising horizon [ http://antwrp.gsfc.nasa.gov/apod/ap990619.html ], stop again, and then set quickly over the other horizon. From Earth [ http://antwrp.gsfc.nasa.gov/apod/ap980530.html ], Mercury's proximity to the Sun [ http://antwrp.gsfc.nasa.gov/apod/ap981212.html ] cause it to be visible only for a short time just after sunset or just before sunrise. |
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Sky and Planets
| Title |
Sky and Planets |
| Explanation |
On February 10th, an evocative [ http://www.jps.net/ssumner/ ] evening sky above Rocklin, California, USA inspired astrophotographer Steve Sumner to record this remarkable sight - five planets and the Moon. Near its first quarter phase, the bright Moon [ http://lunar.arc.nasa.gov/ ] was intentionally overexposed but Saturn [ http://www.jpl.nasa.gov/cassini/ ], Jupiter [ http://galileo.jpl.nasa.gov/ ], Mars [ http://mars.jpl.nasa.gov/ ], and Mercury [ http://sd-www.jhuapl.edu/MESSENGER/ ] (and, of course, planet Earth's [ http://www.earth.nasa.gov/ ] horizon) are all clearly visible in the deepening twilight. Notably absent in this grouping of naked-eye planets is Venus [ http://antwrp.gsfc.nasa.gov/apod/ap990903.html ] which is still putting in an early appearance as the morning star [ http://ispec.scibernet.com/station/morn_star.html ]. This month, Mercury has joined Venus in the dawn twilight while Saturn, Jupiter, and Mars still shine brightly in the western sky at nightfall [ http://www.skypub.com/sights/sights.shtml ] making another gorgeous close grouping with the crescent Moon [ http://www.inconstantmoon.com/ ]. |
|
Slightly Beneath Saturn's Ri
…
| Title |
Slightly Beneath Saturn's Ring Plane |
| Explanation |
When orbiting Saturn, be sure to watch for breathtaking superpositions of moon [ http://antwrp.gsfc.nasa.gov/apod/ap051003.html ]s, rings [ http://antwrp.gsfc.nasa.gov/apod/ap040117.html ], and shadow [ http://antwrp.gsfc.nasa.gov/apod/ap040803.html ]s. One such picturesque vista [ http://photojournal.jpl.nasa.gov/catalog/PIA08146 ] was visible recently to the robot Cassini spacecraft [ http://en.wikipedia.org/wiki/Cassini-Huygens ] now orbiting Saturn. In late February, Cassini captured Rhea [ http://en.wikipedia.org/wiki/Rhea_%28moon%29 ], the second largest moon of Saturn, while looking up from slightly beneath Saturn's expansive ring [ http://antwrp.gsfc.nasa.gov/apod/ap051219.html ] plane. Signature dark gaps [ http://www.planetary.org/saturn/rings.html ] are visible in the nearly edge-on rings. A shadow of Saturn's F ring [ http://antwrp.gsfc.nasa.gov/apod/ap041217.html ] cuts across the cratered ice-moon. Cassini is scheduled [ http://saturn.jpl.nasa.gov/operations/saturn-tour.cfm ] to continue sending back images from the orbit of Saturn until at least 2008. |
|
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. |
|
Skylab Over Earth
| Title |
Skylab Over Earth |
| Explanation |
Skylab [ http://www-pao.ksc.nasa.gov/history/skylab/skylab.htm ] was an orbiting laboratory launched by a Saturn V rocket [ http://antwrp.gsfc.nasa.gov/apod/ap010525.html ] in May 1973. Skylab [ http://heasarc.gsfc.nasa.gov/docs/heasarc/missions/images/skylab_images.html ], pictured above [ http://grin.hq.nasa.gov/ABSTRACTS/GPN-2000-001055.html ], was visited three times by NASA astronauts who sometimes stayed as long as two and a half months. Many scientific tests were performed on Skylab [ http://www.ssl.msfc.nasa.gov/ssl/pad/solar/skylab.htm ], including astronomical observations in ultraviolet [ http://imagers.gsfc.nasa.gov/ems/uv.html ] and X-ray [ http://cxpi.spme.monash.edu.au/xray_history.htm ] light. Some of these observations yielded valuable information about Comet Kohoutek [ http://en.wikipedia.org/wiki/Kohoutek ], our Sun [ http://www.nineplanets.org/sol.html ] and about the mysterious X-ray background [ http://antwrp.gsfc.nasa.gov/apod/ap000114.html ] - radiation that comes from all over the sky. Skylab [ http://en.wikipedia.org/wiki/Skylab ] fell back to earth on 11 July 1979. |
|
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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Descent Panorama of Saturn's
…
| Title |
Descent Panorama of Saturn's Titan |
| Explanation |
You're the first spacecraft ever to descend to Titan -- what do you see? Immediately after the Huygen's probe [ http://en.wikipedia.org/wiki/Huygens_probe ] pierced the cloud deck of Saturn [ http://en.wikipedia.org/wiki/Saturn_%28planet%29 ]'s moon Titan [ http://antwrp.gsfc.nasa.gov/cgi-bin/apod/apod_search?titan ] last January, it took a unique series of pictures of one of the Solar System [ http://www.windows.ucar.edu/our_solar_system/solar_system.html ]'s most mysterious moon's. Those pictures have recently been digitally stitched together to create spectacular panoramas and a dramatic descent movie [ http://photojournal.jpl.nasa.gov/catalog/PIA08117 ]. Pictured above [ http://photojournal.jpl.nasa.gov/catalog/PIA08114 ] is a panoramic fisheye view Huygen's obtained from about five kilometers above Titan's surface [ http://antwrp.gsfc.nasa.gov/apod/ap050117.html ]. The digital projection makes the local surface, mostly flat, appear as a ball, but allows one to see in all directions. Huygen's eventual landing site [ http://antwrp.gsfc.nasa.gov/apod/ap050518.html ] was in the large dark area below, just right of the center. This relatively featureless, dark, sandy basin appears to be surrounded by light colored hills to the right and a landscape fractured by streambeds and canyons [ http://antwrp.gsfc.nasa.gov/apod/ap050124.html ] above. Recent evidence [ http://uanews.org/cgi-bin/WebObjects/UANews.woa/16/wa/MainStoryDetails?ArticleID=12614 ] indicates that Titan's lakebeds and streambeds are usually dry but sometimes filled with a flashflood of liquid methane [ http://en.wikipedia.org/wiki/Methane ] from rare torrents of methane rain [ http://www.astrobio.net/news/article1413.html ]. |
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Saturn in Blue and Gold
| Title |
Saturn in Blue and Gold |
| Explanation |
Why is Saturn partly blue? The above picture [ http://photojournal.jpl.nasa.gov/catalog/PIA08166 ] of Saturn approximates what a human [ http://en.wikipedia.org/wiki/Human ] would see if hovering close to the giant ringed world. The above picture [ http://photojournal.jpl.nasa.gov/catalog/PIA08166 ] was taken in mid-March by the robot Cassini spacecraft [ http://www.esa.int/esaMI/Cassini-Huygens/SEM9D2HHZTD_0.html ] now orbiting Saturn [ http://www.nineplanets.org/saturn.html ]. Here Saturn's majestic rings [ http://en.wikipedia.org/wiki/Saturn%27s_rings ] appear directly only as a thin vertical line. The rings show their complex structure in the dark shadows they create on the image left. Saturn's fountain moon Enceladus [ http://antwrp.gsfc.nasa.gov/apod/ap060310.html ], only about 500 kilometers across, is seen as the bump in the plane of the rings. The northern hemisphere of Saturn can appear partly blue [ http://science.nasa.gov/headlines/y2005/17feb_bluesaturn.htm ] for the same reason that Earth's skies can appear blue [ http://math.ucr.edu/home/baez/physics/General/BlueSky/blue_sky.html ] -- molecules in the cloudless portions of both planet's atmospheres are better at scattering blue light than red. When looking deep into Saturn's clouds [ http://antwrp.gsfc.nasa.gov/apod/ap051010.html ], however, the natural gold hue of Saturn's clouds becomes dominant. It is not known why "southern" Saturn does not show the same blue hue -- one hypothesis holds that clouds are higher there. It is also not known [ http://adsabs.harvard.edu/cgi-bin/nph-bib_query?bibcode=2004cosp.meet..466W ] why Saturn's clouds are colored [ http://antwrp.gsfc.nasa.gov/apod/ap960803.html ] gold. |
|
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 ]. |
|
Planets Above The Clouds
| Title |
Planets Above The Clouds |
| Explanation |
Clouds scatter the faint orange rays of the setting sun [ http://antwrp.gsfc.nasa.gov/apod/ap000115.html ] in the foreground of this breathtaking photograph from the summit [ http://www.ifa.hawaii.edu/mko/mko.html ] of Mauna Kea, Hawaii [ http://antwrp.gsfc.nasa.gov/apod/ap980725.html ]. Taken on April 7th, this skyscape features a dramatic lunar and planetary alignment [ http://antwrp.gsfc.nasa.gov/apod/ap000406.html ]. An overexposed crescent moon [ http://antwrp.gsfc.nasa.gov/apod/ap991108.html ] dominates the celestial scene, but the bright "star" just below and to its right is Saturn [ http://www.jpl.nasa.gov/cassini/Kids/stories/ ] while further below Saturn is a close pairing of brilliant Jupiter [ http://antwrp.gsfc.nasa.gov/apod/ap000429.html ] and a fainter, yellowish Mars [ http://marsnt3.jpl.nasa.gov/education/students.html ]. Red giant star Aldebaran [ http://www.bo.astro.it/copernic/alde-eng.html ] is almost directly above the moon near the top of the image and the bright blue stars of the Pleiades cluster [ http://www.aao.gov.au/images.html/captions/uks018.html ] are visible about midway up and to the right of the moon-Aldebaran line. The good news is that planetary alignments [ http://www.skypub.com/news/special/whypanic.html ] like this one do not portend [ http://tech-two.mit.edu/Shakespeare/Tragedy/macbeth/ macbeth.html ] disasters, are relatively common, and can clearly make inspirational viewing for casual stargazers and astronomers alike. The bad [ http://www.badastronomy.com/bad/misc/planets.html ] news is that the world is not going to end because of the highly publicized planetary alignment [ http://www.griffithobs.org/SkyAlignments.html ] occurring tomorrow, May 5th -- so you probably will have to go to work [ http://www.nasa.gov/newsinfo/alignment.html ]! |
|
Ancient Craters on Saturn's
…
| Title |
Ancient Craters on Saturn's Rhea |
| Explanation |
Saturn's ragged moon Rhea has one of the oldest surfaces known. Estimated as changing little in the past billion years, Rhea [ http://en.wikipedia.org/wiki/Rhea_%28moon%29 ] shows craters [ http://en.wikipedia.org/wiki/Impact_crater ] so old they no longer appear round ? their edges have become compromised by more recent cratering. Like Earth's Moon [ http://antwrp.gsfc.nasa.gov/apod/ap051113.html ], Rhea's rotation is locked on Saturn, and the above image [ http://photojournal.jpl.nasa.gov/catalog/PIA08173 ] shows part of Rhea's surface [ http://antwrp.gsfc.nasa.gov/apod/ap051213.html ] that always faces Saturn. Rhea's leading surface is more highly cratered than its trailing surface. Rhea [ http://antwrp.gsfc.nasa.gov/cgi-bin/apod/apod_search?rhea ] is composed mostly of water-ice but is thought to have a small rocky core. The above image [ http://photojournal.jpl.nasa.gov/catalog/PIA08173 ] was taken by the robot Cassini spacecraft [ http://www.esa.int/esaMI/Cassini-Huygens/SEM9D2HHZTD_0.html ] now orbiting Saturn. Cassini swooped past Rhea two months ago and captured the above image from about 100,000 kilometers away. Rhea [ http://www.nineplanets.org/rhea.html ] spans 1,500 kilometers making it Saturn's second largest moon after Titan [ http://antwrp.gsfc.nasa.gov/apod/ap060215.html ]. Several surface features on Rhea [ http://antwrp.gsfc.nasa.gov/apod/ap050215.html ] remain unexplained including large light patch [ http://antwrp.gsfc.nasa.gov/apod/ap050530.html ]es. |
|
Discovery in Motion
| Title |
Discovery in Motion |
| Explanation |
On July 4th, the space shuttle orbiter Discovery rocketed into space on mission STS-121 [ http://www.nasa.gov/mission_pages/shuttle/main/ index.html ]. Now docked with the International Space Station, Discovery orbits planet Earth [ http://spaceflight.nasa.gov/realdata/tracking/ ] at about 27 thousand kilometers per hour. But in this dramatic sunset view [ http://mediaarchive.ksc.nasa.gov/ detail.cfm?mediaid=28727 ] taken in May, Discovery is approaching the service structures at Kennedy Space Center's launch pad 39B at the blinding speed of (less than) 2 kilometers per hour. Of course, the orbiter [ http://spaceflight.nasa.gov/shuttle/reference/sodb/ ], booster rockets [ http://science.ksc.nasa.gov/shuttle/technology/ sts-newsref/srb.html ], and external fuel tank [ http://science.ksc.nasa.gov/shuttle/technology/ sts-newsref/et.html ] ride on one of NASA's workhorse crawler transporters. Built for the Apollo program to carry the giant Saturn V [ http://antwrp.gsfc.nasa.gov/apod/ap010525.html ] rocket, the crawler transporters [ http://www.nasa.gov/mission_pages/shuttle/behindscenes/ crawlers.html ] have seen four decades of service. |
|
Skylab Over Earth
| Title |
Skylab Over Earth |
| Explanation |
Skylab [ http://heasarc.gsfc.nasa.gov/docs/heasarc/missions/skylab.html ] was an orbiting laboratory launched by a Saturn V rocket [ http://antwrp.gsfc.nasa.gov/apod/ap950829.html ] in May 1973. Skylab [ http://heasarc.gsfc.nasa.gov/docs/heasarc/missions/images/skylab_images.html ] was visited three times by NASA astronauts who sometimes stayed as long as two and a half months. Many scientific tests were performed on Skylab [ http://www.ssl.msfc.nasa.gov/ssl/pad/solar/skylab.htm ], including astronomical observations in ultraviolet [ http://antwrp.gsfc.nasa.gov/apod/lib/glossary.html#uv ] and X-ray [ http://antwrp.gsfc.nasa.gov/apod/lib/glossary.html#X-ray ] light. Some of these observations yielded valuable information about Comet Kohoutek [ http://www.exploratorium.edu/exploring/space/kohoutek.html ], our Sun [ http://antwrp.gsfc.nasa.gov/apod/ap960916.html ] and about the mysterious X-ray background [ http://antwrp.gsfc.nasa.gov/apod/ap000114.html ] - radiation that comes from all over the sky. Skylab [ http://www.xmission.com/~skylab/skylab.html ] fell back to earth on 11 July 1979. |
|
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. |
|
Crescent Rhea Occults Cresce
…
| Title |
Crescent Rhea Occults Crescent Saturn |
| Explanation |
Soft hues, partially lit orbs, a thin trace of the ring, and slight shadows highlight this understated view of the majestic surroundings of the giant planet Saturn. Looking nearly back toward the Sun, the robot Cassini spacecraft [ http://en.wikipedia.org/wiki/Cassini-Huygens ] now orbiting Saturn captured crescent phases [ http://antwrp.gsfc.nasa.gov/apod/ap060618.html ] of Saturn [ http://www.nineplanets.org/saturn.html ] and its moon Rhea [ http://antwrp.gsfc.nasa.gov/apod/ap060530.html ] in color a few months ago. As striking as the above image [ http://photojournal.jpl.nasa.gov/catalog/PIA07806 ] is, it is but a single frame from a recently released 60-frame silent movie where Rhea can be seen gliding in front of its parent world. Since Cassini was nearly in the plane of Saturn's rings [ http://pds-rings.seti.org/saturn/ ], the normally impressive rings are visible here only as a thin line [ http://antwrp.gsfc.nasa.gov/apod/ap051219.html ] across the image center. Cassini has now passed the official half-way mark of its mission around Saturn, but is well situated to complete another two years [ http://saturn.jpl.nasa.gov/news/press-release-details.cfm?newsID=670 ] investigating this complex and surprising system. |
|
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 |
|
Possible Methane Lakes on Ti
…
| Title |
Possible Methane Lakes on Titan |
| Explanation |
Have methane lakes been discovered on Saturn's Titan? That exciting possibility was uncovered from analyses of radar images [ http://antwrp.gsfc.nasa.gov/apod/ap041124.html ] returned last week by the robotic Cassini spacecraft [ http://en.wikipedia.org/wiki/Cassini-Huygens ] now orbiting Saturn. The above image [ http://photojournal.jpl.nasa.gov/catalog/PIA08630 ] is a radar reflection from terrain near Titan's North Pole and spans a region about 200 kilometers across. Evidence [ http://www.planetary.org/blog/article/00000652/ ] that the dark areas might be pools of liquid hydrocarbons [ http://en.wikipedia.org/wiki/Hydrocarbon ] includes an extreme smoothness implied by the lack of a return radar signal [ http://earth.rice.edu/mtpe/geo/geosphere/topics/remotesensing/25_radar.html ], and apparently connected tributaries. If true, Titan would be only the second body in our Solar System [ http://space.jpl.nasa.gov/ ], after Earth, found to possess liquids on the surface. Future observations from Cassini during Titan [ http://saturn.astrobio.net/news/article50.html ] flybys might test the methane [ http://en.wikipedia.org/wiki/Methane ] lake hypothesis, as comparative wind affects on the regions are studied. |
|
Methane Rain Possible on Tit
…
| Title |
Methane Rain Possible on Titan |
| Explanation |
Might it rain cold methane on Saturn's Titan? Recent analyses [ http://www.nature.com/news/2006/060724/full/060724-7.html ] of measurements taken by the Huygen's probe [ http://antwrp.gsfc.nasa.gov/apod/ap060131.html ] that landed on Titan [ http://en.wikipedia.org/wiki/Titan_%28moon%29 ] in 2005 January indicate that the atmosphere is actually saturated with methane [ http://en.wikipedia.org/wiki/Methane ] at a height of about 8 kilometers. Combined with observations of a damp surface [ http://antwrp.gsfc.nasa.gov/apod/ap050117.html ] and lakes [ http://antwrp.gsfc.nasa.gov/apod/ap060731.html ] near the poles, some astrobiologists conclude that at least a methane drizzle [ http://www.nasa.gov/centers/ames/news/releases/2006/06_57AR.html ] is common on parts of Titan. Other astrobiologists reported [ http://www.nature.com/nature/journal/v442/n7101/abs/nature04933.html ] computer models of the clouded moon that indicate that violent methane storms might even occur, complete with flash floods carving channels [ http://antwrp.gsfc.nasa.gov/apod/ap060508.html ] in the landscape. The later scenario is depicted in the above drawing of Titan. Lightning [ http://antwrp.gsfc.nasa.gov/apod/ap040818.html ], as also depicted above, might well exist on Titan but has not been proven. The findings [ http://www.planetary.org/blog/article/00000658/ ] increase speculation that a wet Titanian surface [ http://www.astrobio.net/news/article1766.html ] might be hospitable to unusual forms of life [ http://adsabs.harvard.edu/cgi-bin/nph-bib_query?bibcode=2005Icar..178..274M ]. |
|
The Last Moon Shot
| Title |
The Last Moon Shot |
| Explanation |
In 1865 Jules Verne [ http://www.interlog.com/~anash/najvs.html ] predicted the invention of a space capsule that could carry people. In his science fiction story "From the Earth to the Moon" [ http://JV.Gilead.org.il/pg/moon/ ], he outlined his vision of a cannon in Florida so powerful that it could shoot a "Projectile-Vehicle" [ http://www.nasm.edu/galleries/gal109/NEWHTF/ITM6201.HTM ] carrying three adventurers to the Moon [ http://www.hq.nasa.gov/office/pao/History/ ap11ann/eagle.html ]. Over 100 years later, NASA [ http://www.hq.nasa.gov/pao/History/history.html ], guided by Wernher Von Braun [ http://history.msfc.nasa.gov/vonbraun/index.html ]'s vision, produced the Saturn V rocket [ http://www.apollosaturn.com/ ]. From a spaceport in Florida [ http://www.ksc.nasa.gov/ksc.html ], this rocket turned Verne's fiction into fact, launching 9 Apollo Lunar missions and allowing 12 astronauts to walk on the Moon [ http://www.hq.nasa.gov/office/pao/History/alsj/ ]. Pictured [ http://images.jsc.nasa.gov/images/pao/AS17/10075937.htm ] is the last moon shot, Apollo 17 [ http://nssdc.gsfc.nasa.gov/planetary/lunar/apollo17info.html ], awaiting a night launch in December of 1972. Spotlights play on the rocket and launch pad while the full Moon looms [ http://cass.jsc.nasa.gov/moon.html ] in the background. Humans have not walked on [ http://www.hq.nasa.gov/office/pao/History/alsj/ apollo.epilog.html ] on the lunar surface since. [ http://ilewg.jsc.nasa.gov/ ] |
|
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. |
|
Lightning on Earth
| Title |
Lightning on Earth |
| Explanation |
Nobody knows what causes lightning. It is known that charges [ http://physics.bu.edu/~duffy/PY106/Charge.html ] slowly separate in some clouds [ http://ww2010.atmos.uiuc.edu/(Gh)/guides/mtr/cld/cldtyp/home.rxml ] causing rapid electrical discharges [ http://www.eng.tau.ac.il/Pages/Departments/Inter/edp_lab/ ] (lightning), but how electrical charges [ http://physicsstudio.indstate.edu/java/potential/ProyectI.html ] get separated in clouds [ http://www.geo.mtu.edu/department/classes/ge406/tjbrabec/cloud.html ] remains a topic of much research. Nevertheless, lightning [ http://wvlightning.com/info.html ] bolts are common in clouds during rainstorms, and on average 6000 lightning bolts occur between clouds and the Earth every minute. Above [ http://www.noao.edu/image_gallery/html/im0426.html ], several lightning strokes were photographed behind Kitt Peak National Observatory [ http://www.noao.edu/outreach/kpoutreach.html ] in Arizona [ http://www.state.az.us/ ]. Lightning [ http://bondo.wsc.mass.edu/dept/garp/faculty/lightn.htm ] has also been found on the planets Venus [ http://www.lpl.arizona.edu/~hansell/lightning/poster.html ], Jupiter [ http://antwrp.gsfc.nasa.gov/apod/ap971216.html ], Saturn [ http://learn.jpl.nasa.gov/projectspacef/bkg130b.html ], and Uranus [ http://www.spacetoday.org/SolSys/Uranus/Uranus.html ]. NASA [ http://www.nasa.gov/ ] launched the TRMM mission [ http://trmm.gsfc.nasa.gov/news.html ] in 1997 that continues to measure rainfall and lightning [ http://thunder.msfc.nasa.gov/primer/ ] on planet Earth [ http://antwrp.gsfc.nasa.gov/apod/ap990131.html ]. |
|
Bright Cliffs Across Saturn'
…
| Title |
Bright Cliffs Across Saturn's Moon Dione |
| Explanation |
What causes the bright streaks on Dione? Recent images of this unusual moon by the robot Cassini spacecraft [ http://saturn.jpl.nasa.gov/overview/mission.cfm ] now orbiting Saturn [ http://www.nineplanets.org/saturn.html ] are helping to crack the mystery. Close inspection of Dione's trailing hemisphere, pictured above [ http://photojournal.jpl.nasa.gov/catalog/PIA08256 ], indicates that the white wisps are composed of deep ice cliffs [ http://antwrp.gsfc.nasa.gov/apod/ap051026.html ] dropping hundreds of meters. The cliffs may indicate that Dione has undergone some sort of tectonic surface [ http://www.seismo.unr.edu/ftp/pub/louie/class/100/plate-tectonics.html ] displacements in its past. The bright ice-cliffs run across some of Dione [ http://en.wikipedia.org/wiki/Dione_%28moon%29 ]'s many craters, indicating that the process [ http://adsabs.harvard.edu/cgi-bin/nph-bib_query?bibcode=1984Icar...59..205M ] that created them occurred later than the impacts [ http://antwrp.gsfc.nasa.gov/apod/ap010428.html ] that created those craters. Dione [ http://www.nineplanets.org/dione.html ] is made of mostly water ice but its relatively high density indicates that it contains much rock [ http://en.wikipedia.org/wiki/Rock_and_roll ] inside. Giovanni Cassini [ http://www.seds.org/messier/xtra/Bios/cassini.html ] discovered Dione in 1684. The above image [ http://photojournal.jpl.nasa.gov/catalog/PIA08256 ] was taken at the end of July from a distance of about 263,000 kilometers. Other high resolution image [ http://antwrp.gsfc.nasa.gov/apod/ap951009.html ]s of Dione were taken by the passing Voyager spacecraft [ http://nssdc.gsfc.nasa.gov/planetary/voyager.html ] in 1980. |
|
Eight Planets and New Solar
…
| Title |
Eight Planets and New Solar System Designations |
| Explanation |
How many planets are in the Solar System? This popular question now has a new formal answer according the International Astronomical Union [ http://en.wikipedia.org/wiki/International_Astronomical_Union ] (IAU): eight. Last week, the IAU voted [ http://www.iau2006.org/mirror/www.iau.org/iau0603/index.html ] on a new definition for planet [ http://www.iau2006.org/mirror/www.iau.org/iau0603/index.html ] and Pluto [ http://antwrp.gsfc.nasa.gov/apod/ap010319.html ] did not make the cut. Rather, Pluto was re-classified as a dwarf planet [ http://en.wikipedia.org/wiki/Dwarf_planet ] and is considered as a prototype for a new category of trans-Neptunian objects [ http://en.wikipedia.org/wiki/Trans-Neptunian_object ]. The eight planets now recognized by the IAU are: Mercury [ http://antwrp.gsfc.nasa.gov/apod/ap040912.html ], Venus [ http://antwrp.gsfc.nasa.gov/apod/ap040516.html ], Earth [ http://antwrp.gsfc.nasa.gov/apod/ap050102.html ], Mars [ http://antwrp.gsfc.nasa.gov/apod/ap060730.html ], Jupiter [ http://antwrp.gsfc.nasa.gov/apod/ap050911.html ], Saturn [ http://antwrp.gsfc.nasa.gov/apod/ap041225.html ], Uranus [ http://antwrp.gsfc.nasa.gov/apod/ap010826.html ], and Neptune [ http://antwrp.gsfc.nasa.gov/apod/ap010821.html ]. Solar System objects now classified as dwarf planets are: Ceres [ http://antwrp.gsfc.nasa.gov/apod/ap060821.html ], Pluto [ http://antwrp.gsfc.nasa.gov/apod/ap060624.html ], and the currently unnamed 2003 UB313 [ http://antwrp.gsfc.nasa.gov/apod/ap060207.html ]. Planets, by the new IAU definition, must be in orbit around the sun, be nearly spherical, and must have cleared the neighborhood around their orbits. The demotion of Pluto [ http://www.nineplanets.org/pluto.html ] to dwarf planet status is a source of continuing dissent [ http://www.badastronomy.com/bablog/2006/08/18/colbert-takes-neil-tyson-down/ ] and controversy [ http://newswire.ascribe.org/cgi-bin/behold.pl?ascribeid=20060818.063045&time=07%2006%20PDT&year=2006&public=0 ] in the astronomical community. |
|
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. |
|
Moon And Venus Share The Sky
| Title |
Moon And Venus Share The Sky |
| Explanation |
July is drawing to a close and in the past few days, some early morning risers [ http://antwrp.gsfc.nasa.gov/apod/ap990714.html ] could have looked east and seen a crescent Moon sharing the pre-dawn [ http://science.nasa.gov/headlines/y2000/ast25jul_1m.htm ] skies with planets Jupiter and Saturn. Planet Mercury will also pass about 2 degrees from the thin waning crescent Moon [ http://aa.usno.navy.mil/AA/faq/docs/moon_phases.html ] just before sunrise near the eastern horizon on Saturday, July 29. And finally, on the evening of July 31st, Venus will take its turn near the crescent Moon [ http://antwrp.gsfc.nasa.gov/apod/ap991108.html ]. But this time it will be a day-old crescent Moon near the western horizon, shortly after sunset [ http://antwrp.gsfc.nasa.gov/apod/ap000507.html ]. In fact [ http://pages.prodigy.net/pam.orman/JoeAlmanac2000.html ], on July 31 (August 1 Universal Time) the Moon will occult [ http://www.skypub.com/sights/occultations/lunar/ 0001lunarocc.html ] (pass in front of) Venus for northwestern observers [ http://www.skypub.com/sights/images2000/ 0008moonvenus_big.jpg ] in North America. This telescopic picture taken on 31 December 1997, shows a lovely young crescent Moon and brilliant crescent Venus in [ http://antwrp.gsfc.nasa.gov/apod/ap990903.html ] the early evening sky near Bursa, Turkey [ http://www.mersina.com/Turkey/Marmara/Bursa/index.html ]. And what about the Sun? On Sunday, July 30, a partial eclipse of the Sun [ http://sunearth.gsfc.nasa.gov/eclipse/extra/ PSE2000Jul31.html ] will be visible from some locations [ http://sunearth.gsfc.nasa.gov/eclipse/OH/ PSE2000Jul.gif ] in North America. |
|
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 ]. |
|
Saturn's Infrared Glow
| Title |
Saturn's Infrared Glow |
| Explanation |
Known for its bright ring [ http://antwrp.gsfc.nasa.gov/apod/ap040117.html ] system and many moons [ http://antwrp.gsfc.nasa.gov/apod/ap051021.html ], gas giant Saturn looks strange and unfamiliar in this false-color view from the Cassini spacecraft. In fact, in this [ http://photojournal.jpl.nasa.gov/catalog/PIA08732 ] Visual and Infrared Mapping Spectrometer (VIMS [ http://wwwvims.lpl.arizona.edu/ ]) mosaic the famous rings are almost invisible, seen edge-on cutting across picture center. The most striking contrast in the image is along the terminator or boundary between night and day. To the right (day side) blue-green hues are visible sunlight reflected from Saturn's cloud tops. But on the left (night side) in the absence of sunlight, the lantern-like [ http://saturn.jpl.nasa.gov/news/ press-release-details.cfm?newsID=694 ] glow of infrared radiation from the planet's warm interior silhouettes features at Saturn's deeper [ http://saturn.jpl.nasa.gov/news/ press-release-details.cfm?newsID=696 ] cloud levels. The thermal infrared glow [ http://coolcosmos.ipac.caltech.edu//image_galleries/ ir_zoo/index.html ] is also apparent in the broad bands of ring shadows [ http://antwrp.gsfc.nasa.gov/apod/ap050504.html ] draped across the northern hemisphere of Saturn [ http://en.wikipedia.org/wiki/Saturn_(planet) ]. |
|
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. |
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The Surface of Titan
| Title |
The Surface of Titan |
| Explanation |
If sailing the hydrocarbon [ http://chemscape.santafe.cc.fl.us/chemscape/glossary/hdef.htm#24 ] seas of Titan [ http://antwrp.gsfc.nasa.gov/apod/ap990207.html ], beware of gasoline rain. Such might be a travel advisory [ http://travel.state.gov/travel_warnings.html ] issued one future day for adventurers visiting Titan [ http://antwrp.gsfc.nasa.gov/apod/ap000820.html http://www.seds.org/nineplanets/nineplanets/titan.html ], the largest moon of Saturn [ http://www.seds.org/nineplanets/nineplanets/saturn.html ]. New images of Titan [ http://antwrp.gsfc.nasa.gov/apod/ap951021.html ]'s surface were released [ http://despa.obspm.fr/planeto/titan_pueo.html ] last week from the Canada-France Hawaii Telescope [ http://www.cfht.hawaii.edu/ ] featuring the finest details [ http://adsabs.harvard.edu/cgi-bin/nph-bib_query?bibcode=1999DPS....31.4103C ] yet resolved. Peering into Titan [ http://ispec.scibernet.com/student-pages/saturn/titan.html ]'s thick smog [ http://www.aqmd.gov/smog/inhealth.html ] atmosphere with infrared [ http://www.us-gemini.noao.edu/public/infrared.html ] light, complex features interpreted as oceans, glaciers [ http://uanews.opi.arizona.edu/cgi-bin/WebObjects/ScienceResearch.woa/wo/XoEuK0m1padNGJ00ob/0.11.0.3?ArticleID=1926 ], and rock became visible. The high-resolution infrared image pictured above [ http://despa.obspm.fr/planeto/titan_pueo.html ] was made possible using an unblurring [ http://antwrp.gsfc.nasa.gov/apod/ap000725.html ] technique called adaptive optics [ http://www.lyot.obspm.fr/adaptive_optics.html ]. The interplanetary probe Cassini [ http://www.jpl.nasa.gov/cassini/ ] will reach Saturn and Titan in 2004 to better explore [ http://antwrp.gsfc.nasa.gov/apod/ap970829.html ] this unusual world. |
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A Hurricane Over the South P
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| Title |
A Hurricane Over the South Pole of Saturn |
| Explanation |
What's happening at the south pole of Saturn? To find out, scientists sent the robot Cassini probe [ http://en.wikipedia.org/wiki/Cassini-Huygens ] now orbiting Saturn [ http://eightplanets.org/saturn.html ] directly over the lower spin axis of the ringed giant. Cassini found there a spectacular massive swirling storm system with a well developed eye-wall, similar to a hurricane here on Earth [ http://antwrp.gsfc.nasa.gov/apod/ap040915.html ]. One image of the storm is shown above [ http://photojournal.jpl.nasa.gov/catalog/PIA08332 ], while several frames from the overpass have been made into a movie that shows the huge vortex rotating [ http://video.google.com/videoplay?docid=8112690528797127090 ]. The storm is slightly larger than the entire Earth and carries winds that reach 550 kilometers per hour, twice the velocity of a Category 5 [ http://en.wikipedia.org/wiki/Saffir-Simpson_Hurricane_Scale ] hurricane. This pole vortex on Saturn might have been raging for billions of years and is not expected to drift off [ http://antwrp.gsfc.nasa.gov/apod/ap040919.html ] the pole. |
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Saturnian Aurora
| Title |
Saturnian Aurora |
| Explanation |
Girdling the second largest planet [ http://www.seds.org/nineplanets/nineplanets/saturn.html ] in the Solar System, Saturn's Rings [ http://antwrp.gsfc.nasa.gov/apod/ap971029.html ] are one of the most spectacular sights for earthbound telescopes. This image [ http://oposite.stsci.edu/pubinfo/pr/1998/05/ ] from the orbiting Hubble Space Telescope [ http://www.stsci.edu/hst/ ]'s STIS instrument [ http://www.ball.com/aerospace/stis.html ], offers a striking view of another kind of ring around Saturn [ http://antwrp.gsfc.nasa.gov/apod/ap970829.html ] - pole encircling rings [ http://antwrp.gsfc.nasa.gov/apod/ap970402.html ] of ultraviolet [ http://imagine.gsfc.nasa.gov/docs/science/know_l1/emspectrum.html ] aurora [ http://www.geo.mtu.edu/weather/aurora/ ]. Towering more than 1,000 miles above the cloud tops [ http://antwrp.gsfc.nasa.gov/apod/ap960317.html ], these Saturnian auroral displays are analogous to Earth's [ http://antwrp.gsfc.nasa.gov/apod/ap970418.html ]. Energetic charged particles in the Solar Wind [ http://antwrp.gsfc.nasa.gov/apod/ap000318.html ] are funneled by the planet's magnetic field into polar regions where they interact with [ http://antwrp.gsfc.nasa.gov/apod/ap961130.html ] atmospheric gases. Following the ebb and flow of Saturn's aurora [ http://adsabs.harvard.edu/cgi-bin/nph-bib_query?bibcode=1998DPS....30.4301T ], researchers can remotely explore the planet's atmosphere and magnetic field [ http://www.nasm.edu/ceps/etp/saturn/satmagnet.html ]. In this false color image [ http://oposite.stsci.edu/pubinfo/pr/1998/05/ ], the dramatic red aurora identify emission from atomic hydrogen [ http://pearl1.lanl.gov/periodic/elements/1.html ], while the more concentrated white areas are due to hydrogen molecules [ http://www.exploratorium.edu/xref/phenomena/atoms_and_molecules.html ]. In 2004, NASA plans to begin making close-up studies of the Saturnian system [ http://www.solarviews.com/eng/saturn.htm ] with the Cassini Spacecraft [ http://www.jpl.nasa.gov/cassini/ ]. |
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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. |
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Mysterious Spokes in Saturn'
…
| Title |
Mysterious Spokes in Saturn's Rings |
| Explanation |
What causes the mysterious spokes in Saturn's rings? Visible on the left of the above image [ http://photojournal.jpl.nasa.gov/catalog/PIA08316 ] as ghostlike impressions, spokes were first discovered by the Voyager spacecraft [ http://en.wikipedia.org/wiki/Voyager_1 ] that buzzed by Saturn in the early 1980s. Their existence was unexpected, and no genesis hypothesis has ever become accepted. Oddly, the spokes [ http://csep10.phys.utk.edu/astr161/lect/saturn/rings.html ] were conspicuously absent [ http://adsabs.harvard.edu/cgi-bin/nph-bib_query?bibcode=2005DPS....37.6111M ] from initial images sent back by the robot Cassini spacecraft [ http://saturn.jpl.nasa.gov/spacecraft/ ] now orbiting Saturn. Analyses of archived Voyager [ http://antwrp.gsfc.nasa.gov/apod/ap020831.html ] images have led to the conclusions that the transient spokes, which may form and dissipate over a few hours, are composed of electrically charged sheets of small dust-sized particles. Some recent images from Cassini like that shown above [ http://photojournal.jpl.nasa.gov/catalog/PIA08316 ] have now finally shown the enigmatic spokes superposed on Saturn's B ring [ http://antwrp.gsfc.nasa.gov/apod/ap050525.html ]. Hypotheses for spoke creation include small meteors impacting the rings and electron beams [ http://adsabs.harvard.edu/cgi-bin/nph-bib_query?bibcode=2006GeoRL..3321202J ] from Saturnian atmospheric lightning spraying [ http://www.nature.com/news/2006/061120/full/061120-14.html ] the rings. Observations of the puzzling spokes, as well as creative origin speculations, are ongoing. |
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Janus: Potato Shaped Moon of
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| Title |
Janus: Potato Shaped Moon of Saturn |
| Explanation |
Janus is one of the stranger moons of Saturn. First, Janus [ http://www.planetary.org/explore/topics/saturn/janus.html ] travels in an unusual orbit around Saturn where it periodically trades places with its sister moon Epimetheus [ http://antwrp.gsfc.nasa.gov/apod/ap050429.html ], which typically orbits about 50 kilometers away. Janus [ http://en.wikipedia.org/wiki/Janus_%28moon%29 ], although slightly larger than Epimetheus [ http://antwrp.gsfc.nasa.gov/apod/ap050824.html ], is potato [ http://en.wikipedia.org/wiki/Potato ]-shaped and has a largest diameter of about 190 kilometers. Next, Janus is covered with large craters but strangely appears to lack small craters. One possible reason for this is a fine dust that might cover the small moon, a surface also hypothesized for Pandora [ http://antwrp.gsfc.nasa.gov/apod/ap051123.html ] and Telesto [ http://antwrp.gsfc.nasa.gov/apod/ap060222.html ]. Pictured above [ http://photojournal.jpl.nasa.gov/catalog/PIA08296 ], Janus was captured in front of the cloud tops [ http://antwrp.gsfc.nasa.gov/apod/ap051010.html ] of Saturn [ http://en.wikipedia.org/wiki/Saturn ] in late September. |
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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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Saturn Rotates
| Title |
Saturn Rotates |
| Explanation |
The dramatic rotation of the cloud-tops of Saturn [ http://www.seds.org/nineplanets/nineplanets/saturn.html ] every ten-hours is particularly evident from orbit around the gas giant planet. With a good enough telescope, however, such rotation is visible even from Earth, as shown by this time-lapse image sequence [ http://www.jpl.nasa.gov/saturn/anim1.html ] from the Hubble Space Telescope [ http://www.stsci.edu/hst/ ] taken in November 1990. Particularly evident at that time was a light-colored giant storm cloud system [ http://adsabs.harvard.edu/cgi-bin/nph-bib_query?bibcode=1999Icar..137...24A ] that completely encircled the planet. The storm was not evident twenty years ago during the flybys of the Voyager spacecraft [ http://vraptor.jpl.nasa.gov/voyager/voyager.html ] -- a storm of this magnitude was last noted in 1933. Studying the complex atmosphere [ http://antwrp.gsfc.nasa.gov/apod/ap000926.html ] of Saturn will be one objective of the Cassini [ http://www.jpl.nasa.gov/cassini/ ] spacecraft launched [ http://antwrp.gsfc.nasa.gov/apod/ap971016.html ] by NASA in 1997 and expected to arrive in 2004. |
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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 ]. |
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Cassini Spacecraft Approache
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| Title |
Cassini Spacecraft Approaches Jupiter |
| Explanation |
A new spacecraft has entered the outer Solar System: Cassini [ http://www.jpl.nasa.gov/cassini/english/spacecraft/ ]. Launched in 1997 [ http://antwrp.gsfc.nasa.gov/apod/ap971016.html ] and bound for Saturn in 2004, Cassini sent back the above image [ http://ciclops.lpl.arizona.edu/ciclops/Images_jupiter.html ] last week while approaching the giant planet Jupiter [ http://www.seds.org/nineplanets/nineplanets/jupiter.html ]. Cassini [ http://quest.arc.nasa.gov/saturn/qa/cassini/ ] joins the Galileo spacecraft [ http://www.jpl.nasa.gov/galileo/mission.html] currently in orbit around Jupiter in studying the gas giant and its moons. In fact, observations [ http://www.jpl.nasa.gov/releases/2000/glextended.html ] involving both spacecraft [ http://www.jpl.nasa.gov/jupiterflyby/ ] simultaneously are planned in the coming months. This color picture [ http://photojournal.jpl.nasa.gov/cgi-bin/ PIAGenCatalogPage.pl?PIA02972 ] was taken when Cassini was 81.3 million kilometers from Jupiter. The alternating dark and bright bands characteristic of Jupiter's cloud tops [ http://antwrp.gsfc.nasa.gov/apod/ap000429.html ] can be easily seen. Jupiter's moon Europa [ http://antwrp.gsfc.nasa.gov/apod/ap000825.html ] is also seen at the far right of the image casting a round shadow on the planet. |
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New Moons For Saturn
| Title |
New Moons For Saturn |
| Explanation |
Which planet has the most moons? For now, it's Saturn. Four newly discovered [ http://www.eso.org/outreach/press-rel/pr-2000/ phot-29-00.html ] satellites bring the ringed planet's total to twenty-two, just edging out Uranus' [ http://antwrp.gsfc.nasa.gov/apod/ap971103.html ] twenty-one for the most known [ http://www.eso.org/outreach/press-rel/pr-2000/ phot-19-00.html ] moons in the solar system. Of course, the newfound Saturnian satellites [ http://www.nasm.edu/ceps/etp/saturn/satmoons.html ] are not large [ http://antwrp.gsfc.nasa.gov/apod/ap000820.html ] and photogenic [ http://antwrp.gsfc.nasa.gov/apod/ap000129.html ]. The faint S/2000 S 1, the first discovered in the year 2000, is the tiny dot indicated at the lower right of this August 7th image made with the ESO 2.2 meter telescope at La Silla, Chile [ http://www.ls.eso.org/index.html ]. (An eye-catching spiral galaxy at the upper left is in the very distant background!) Unlike Saturn's larger moons whose almost circular orbits lie near the planet's equatorial plane, all four newly discovered moons have irregular [ http://www.obs-nice.fr/gladman/urhome.html ], skewed orbits drifting far from the planet. With sizes in the 10 to 50 kilometer range, they are are likely captured asteroids. The international team of astronomers involved in the discoveries hopes to get many observations of the tiny satellites [ http://www.obs-nice.fr/saturn/ ] allowing accurate orbital computations before Saturn is [ http://www.jpl.nasa.gov/cassini/ ] lost in the solar glare around March 2001. The team has also found several other irregular satellite candidates which are now being followed. Saturn's only previously known irregular satellite is Phoebe [ http://seds.lpl.arizona.edu/nineplanets/nineplanets/ phoebe.html ], discovered over 100 years ago by W. H. Pickering, |
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October Skylights
| Title |
October Skylights |
| Explanation |
With brilliant Venus [ http://nssdc.gsfc.nasa.gov/planetary/factsheet/ venusfact.html ] above the western horizon at sunset and Jupiter [ http://galileo.jpl.nasa.gov/ ] and Saturn [ http://www.jpl.nasa.gov/cassini/ ] high in the east by early evening, November's night sky is filled with bright planets. October's sky featured bright planets as well and, triggered by the active Sun, some lovely auroral displays [ http://www.exploratorium.edu/learning_studio/ auroras/ ]. This colorful aurora was recorded by astrophotographer Wade Clark in skies above Hamilton, Washington, USA on the night of October 4th. Through the shimmering northern lights [ http://climate.gi.alaska.edu/Curtis/aurora/ aurora.html ] Jupiter and Saturn are easy to spot [ http://antwrp.gsfc.nasa.gov/apod/ap000929.html ] flanking the V-shaped head of Taurus [ http://server.remc12.k12.mi.us/csplanet/myth/ taurus.html ] the Bull. Of course, just above lies the lovely Pleiades star cluster. Solar activity [ http://spaceweather.com/ ] will also produce auroral shows in November, particularly at high northern and southern latitudes. Plus, November skygazers can certainly anticipate a celestial performance on the evening of the 17th/18th -- the moonlit Leonid meteor shower [ http://spacescience.com/headlines/y2000/ast10oct_1.htm ]. |
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A Year of Extraterrestrial F
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| Title |
A Year of Extraterrestrial Fountains and Flows |
| Explanation |
The past year was extraordinary for the discovery of extraterrestrial fountains and flows -- some offering new potential in the search for liquid water and the origin of life beyond planet Earth.. Increased evidence was uncovered that fountains [ http://antwrp.gsfc.nasa.gov/apod/ap060608.html ] spurt not only from Saturn's moon Enceladus [ http://antwrp.gsfc.nasa.gov/apod/ap060310.html ], but from the dunes of Mars [ http://antwrp.gsfc.nasa.gov/apod/ap060823.html ] as well. Lakes were found on Saturn's moon Titan [ http://antwrp.gsfc.nasa.gov/apod/ap060731.html ], and the residual of a flowing liquid was discovered on the walls of Martian craters [ http://antwrp.gsfc.nasa.gov/apod/ap061212.html ]. The diverse Solar System [ http://en.wikipedia.org/wiki/Solar_system ] fluidity may involve forms of slushy water-ice, methane [ http://scifun.chem.wisc.edu/chemweek/methane/methane.html ], or sublimating [ http://en.wikipedia.org/wiki/ Sublimation_%28physics%29 ] carbon dioxide [ http://scifun.chem.wisc.edu/chemweek/CO2/CO2.html ]. Pictured above [ http://antwrp.gsfc.nasa.gov/apod/ap061231.html http://photojournal.jpl.nasa.gov/catalog/PIA09028 ], the light-colored path below the image center is hypothesized to have been created sometime in just the past few years by liquid water flowing [ http://www.nasa.gov/mission_pages/mars/news/mgs-20061206.html ] across the surface of Mars [ http://antwrp.gsfc.nasa.gov/apod/mars.html ]. |
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Liquid Lakes on Saturn's Tit
…
| Title |
Liquid Lakes on Saturn's Titan |
| Explanation |
Why would some regions on Titan reflect very little radar? The leading explanation is that these regions are lakes, possibly composed of liquid methane. The above image [ http://photojournal.jpl.nasa.gov/catalog/PIA09102 ] is a false-color synthetic radar map of a northern region of Titan [ http://saturn.astrobio.net/news/article50.html ] taken during a flyby of the cloudy moon [ http://antwrp.gsfc.nasa.gov/apod/ap040810.html ] by the robotic Cassini spacecraft [ http://en.wikipedia.org/wiki/Cassini-Huygens ] last July. On this map, which spans about 150 kilometers across, dark regions reflect relatively little of the broadcast radar [ http://earth.rice.edu/mtpe/geo/geosphere/topics/remotesensing/25_radar.html ] signal. Images like this show Titan [ http://antwrp.gsfc.nasa.gov/apod/ap050117.html ] to be only the second body in the Solar System [ http://space.jpl.nasa.gov/ ] to possess liquids on the surface. Future observations from Cassini during Titan flybys [ http://saturn.jpl.nasa.gov/operations/saturn-tour.cfm ] will further test the methane [ http://en.wikipedia.org/wiki/Methane ] lake hypothesis, as comparative wind effects on the regions are studied. |
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