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|
Best images yet of Thebe, Am
…
These images of the inner Jo
…
4/24/00
| Date |
4/24/00 |
| Description |
These images of the inner Jovian moons Thebe, Amalthea, and Metis (left to right), taken in January 2000 by the camera onboard NASA's Galileo spacecraft, are the highest-resolution images ever obtained of these small, irregularly shaped satellites. The images resolve surface features as small as 2 kilometers (about 1.2 miles) across for Thebe, 2.4 kilometers (about 1.5 miles) across for Amalthea, and 3 kilometers (about 1.9 miles) across for Metis. In late 1999 and early 2000, near the end of a two-year mission extension known as the Galileo Europa Mission, the Galileo spacecraft dipped closer to Jupiter than it had been since it first went into orbit around the giant planet in 1995. These maneuvers allowed Galileo to make three flybys of the volcanically active moon Io and also made possible these new high-quality images of Thebe, Amalthea, and Metis, which lie very close to Jupiter, inside the orbit of Io. The moons are shown in their correct relative sizes, with sunlight coming from the right. These views show the side of each moon that faces permanently away from Jupiter, and north is approximately up in all cases. The prominent impact crater on Thebe is about 40 kilometers (about 25 miles) across and has been given the provisional name Zethus. The large white region near the south pole of Amalthea marks the location of the brightest patch of surface material seen anywhere on these three moons. This unusual material, which sits inside a large crater named Gaea, has been greatly overexposed, accordingly, the white area on this image is somewhat larger than the actual bright area on Amalthea. Note also the "scalloped" or "sawtooth" shape of Amalthea's terminator (the line between day and night, at the left-hand edge of Amalthea's disk), which indicates that parts of this satellite's surface are very rough, with many small hills and valleys. The images are, from left to right: Thebe taken January 4, 2000 at a range of 193,00 kilometers (about 120,000 miles), Amalthea taken January 4, 2000 at a range of 238,000 kilometers (about 176,000 miles), Metis taken on January 4, 2000 at a range of 293,000 kilometers (about 182,000 miles). # # # # # |
|
Galileo Earth Views (WMS)
| Title |
Galileo Earth Views (WMS) |
| Abstract |
The Galileo spacecraft was launched from the Space Shuttle Atlantis on October 18, 1989 on a six-year trip to Jupiter. On the way, the trajectory of the spacecraft took it past Venus once and Earth twice. Galileo took the Earth images in this animation just after the first flyby of the Earth, on December 11 and 12, 1990. This six-hour sequence of images taken two minutes apart clearly shows how the Earth looks from space and how fast (or slow) the cloud features change when looked at from a distance. The path of the sun can be seen crossing Australia by its reflection in the nearby ocean, and the terminator region between night and day can be seen moving across the Indian Ocean. In the original images, the Earth's rotation is so dominant that cloud movement is hard to see, but these images have been mapped to the Earth is such a way that a viewer can watch just the clouds move in the ocean around Antarctica or across the Austrailian land mass. In this animation, New Zealand can ony be seen as a stationary disturbance under a moving cloud bank. The black area with the sharp boundary to the north and east of Australia is the side of the Earth that could not be seen from Galileo's position. |
| Completed |
2004-08-06 |
|
Lunar Beauty Shot
| Title |
Lunar Beauty Shot |
| Abstract |
This is a beauty shot animation flying over the surface of the moon created in support of a series of live interviews about the 2004 lunar eclipse. Scales are not accurate in this visualization. The Earth is about 3 times larger than it would actually appear. The source of the moon texture is unknown, it is thought to be a composite from several missions. The Earth texture was captured as the Galileo spacecraft swung by the Earth in 1990 for a gravity assist on its way to Jupiter. |
| Completed |
2004-11-01 |
|
Simulations of the Breakup o
…
| Title |
Simulations of the Breakup of Comet Shoemaker-Levy 9 Employing a Swarm Model: Dynamical Evolution |
| Abstract |
The breakup of comet Shoemaker-Levy 9 due to its gravitational interaction with Jupiter in July, 1994 is simulated using a swarm model. In this simulation, the comet is modeled as an initially spherical distribution of 16,384 particles. The particles interact with the tidal field of Jupiter and with each other through inter-particle gravitation and collisions. All simulations were performed on the Maspar MP-2 at NASA/GSFC. |
| Completed |
1995-03-24 |
|
Simulations of the Breakup o
…
| Title |
Simulations of the Breakup of Comet Shoemaker-Levy 9 Employing a Swarm Model: Initial Conditions |
| Abstract |
The breakup of comet Shoemaker-Levy 9 due to its gravitational interaction with Jupiter in July, 1994 is simulated using a swarm model. In this simulation, the comet is modeled as an initially spherical distribution of 16,384 particles. The particles interact with the tidal field of Jupiter and with each other through inter-particle gravitation and collisions. All simulations were performed on the Maspar MP-2 at NASA/GSFC. |
| Completed |
1995-03-24 |
|
Europa's Synthetic Subsurfac
…
| Title |
Europa's Synthetic Subsurface Heat Transport (Version 2) |
| Abstract |
Encounters with Jupiter's moon Europa by the Voyager and Galileo spacecraft indicated that a liquid salty ocean might exist below a layer of surface ice that is up to 10 kilometers thick. An ocean general circulation model developed to study the earth's oceans was used to investigate the tidally-forced ocean circulations on Europa. The orbit of Europa is 'gravity locked' so that the same side of Europa always faces Jupiter as is the case with the earth's moon. The icy surface of Europa heaves up and down 50 meters due to the strong tidal forces. This visualization shows the temperature changes induced from the flow fields calculated for a European ocean 50 kilometers deep. The warmest temperatures tend to be near the equator, not because of heating by the sun, but because the currents in the European ocean move the warmest waters to that location. Understanding the thermal and flow fields from these model runs will help to interpret observations from future missions to Europa such as the Jupiter's Icy Moons Orbiter mission proposed for launch in 2012. |
| Completed |
2004-05-04 |
|
Europa's Synthetic Subsurfac
…
| Title |
Europa's Synthetic Subsurface Heat Transport (Version 2) |
| Abstract |
Encounters with Jupiter's moon Europa by the Voyager and Galileo spacecraft indicated that a liquid salty ocean might exist below a layer of surface ice that is up to 10 kilometers thick. An ocean general circulation model developed to study the earth's oceans was used to investigate the tidally-forced ocean circulations on Europa. The orbit of Europa is 'gravity locked' so that the same side of Europa always faces Jupiter as is the case with the earth's moon. The icy surface of Europa heaves up and down 50 meters due to the strong tidal forces. This visualization shows the temperature changes induced from the flow fields calculated for a European ocean 50 kilometers deep. The warmest temperatures tend to be near the equator, not because of heating by the sun, but because the currents in the European ocean move the warmest waters to that location. Understanding the thermal and flow fields from these model runs will help to interpret observations from future missions to Europa such as the Jupiter's Icy Moons Orbiter mission proposed for launch in 2012. |
| Completed |
2004-05-04 |
|
Europa's Synthetic Subsurfac
…
| Title |
Europa's Synthetic Subsurface Heat Transport (Version 2) |
| Abstract |
Encounters with Jupiter's moon Europa by the Voyager and Galileo spacecraft indicated that a liquid salty ocean might exist below a layer of surface ice that is up to 10 kilometers thick. An ocean general circulation model developed to study the earth's oceans was used to investigate the tidally-forced ocean circulations on Europa. The orbit of Europa is 'gravity locked' so that the same side of Europa always faces Jupiter as is the case with the earth's moon. The icy surface of Europa heaves up and down 50 meters due to the strong tidal forces. This visualization shows the temperature changes induced from the flow fields calculated for a European ocean 50 kilometers deep. The warmest temperatures tend to be near the equator, not because of heating by the sun, but because the currents in the European ocean move the warmest waters to that location. Understanding the thermal and flow fields from these model runs will help to interpret observations from future missions to Europa such as the Jupiter's Icy Moons Orbiter mission proposed for launch in 2012. |
| Completed |
2004-05-04 |
|
Europa's Synthetic Subsurfac
…
| Title |
Europa's Synthetic Subsurface Heat Transport (Version 2) |
| Abstract |
Encounters with Jupiter's moon Europa by the Voyager and Galileo spacecraft indicated that a liquid salty ocean might exist below a layer of surface ice that is up to 10 kilometers thick. An ocean general circulation model developed to study the earth's oceans was used to investigate the tidally-forced ocean circulations on Europa. The orbit of Europa is 'gravity locked' so that the same side of Europa always faces Jupiter as is the case with the earth's moon. The icy surface of Europa heaves up and down 50 meters due to the strong tidal forces. This visualization shows the temperature changes induced from the flow fields calculated for a European ocean 50 kilometers deep. The warmest temperatures tend to be near the equator, not because of heating by the sun, but because the currents in the European ocean move the warmest waters to that location. Understanding the thermal and flow fields from these model runs will help to interpret observations from future missions to Europa such as the Jupiter's Icy Moons Orbiter mission proposed for launch in 2012. |
| Completed |
2004-05-04 |
|
Super-Earths May Circle Othe
…
| Title |
Super-Earths May Circle Other Stars |
| Explanation |
Are "super-Earths" common around other star systems? Quite possibly. Unexpected evidence [ http://www.cfa.harvard.edu/press/pr0614.html ] for this came to light recently when a planet orbiting a distant star gravitationally magnified [ http://astron.berkeley.edu/~jcohn/lens.html ] the light of an even more distant star. Assuming the planet's parent star is normal red dwarf [ http://en.wikipedia.org/wiki/Red_dwarf ], the brightening is best explained if the planet is about 13 times the mass of the Earth [ http://antwrp.gsfc.nasa.gov/apod/ap030324.html ] and orbiting at the distance of the asteroid belt [ http://antwrp.gsfc.nasa.gov/apod/ap060319.html ] in our own Solar System [ http://space.jpl.nasa.gov/ ]. Given the small number of objects observed and similar determinations already obtained for other star systems, these super-Earths might be relatively common. Astronomers speculate [ http://arxiv.org/PS_cache/astro-ph/pdf/0603/0603276.pdf ] that the planet might have grown into a Jupiter-sized [ http://antwrp.gsfc.nasa.gov/apod/ap050911.html ] planet if its star system had more gas. Since the planet was not observed directly, significant uncertainty [ http://www.aip.org/history/heisenberg/p08c.htm ] remains in its defining attributes, and future research will be aimed at better understanding this intriguing system. The above drawing [ http://www.cfa.harvard.edu/press/pr0614image.html ] gives an artist's depiction of what a super-Earth orbiting a distant red dwarf [ http://imagine.gsfc.nasa.gov/docs/science/know_l2/stars.html ] star might look like, complete with a hypothetical moon [ http://antwrp.gsfc.nasa.gov/apod/ap050805.html ]. |
|
Red Spot Jr.
| Title |
Red Spot Jr. |
| Explanation |
Jupiter's Great Red Spot [ http://heritage.stsci.edu/1999/29/ index.html ] is a swirling storm seen for over 300 years, since the beginning of telescopic observations of the Solar System's ruling gas giant [ http://antwrp.gsfc.nasa.gov/apod/ap030906.html ]. But over the last month it has been joined by Red Spot Jr [ http://science.nasa.gov/headlines/y2006/ 02mar_redjr.htm ]. Thought to be similar to the Great Red Spot itself, this not-so-great red spot was actually seen to form as smaller whitish oval-shaped [ http://antwrp.gsfc.nasa.gov/apod/ap981022.html ] storms merged and then developed [ http://jupiter.cstoneind.com/ ] the remarkable reddish hue. This webcam image showing [ http://www.iceinspace.com.au/ ] the two red tinted Jovian storms was recorded on the morning of March 12 from the Central Coast of New South Wales, Australia - part of a series showing Jupiter's rotation. Similar in diameter to planet Earth, Red Spot Jr. [ http://skyandtelescope.com/news/article_1689_1.asp ] is expected to last for a while, and trails the Great Red Spot by about an hour as the planet rotates. Astronomers still don't exactly understand why Jupiter's red spots are red [ http://antwrp.gsfc.nasa.gov/apod/ap960803.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. |
|
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. |
|
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/ ]. |
|
Zal Patera on Jupiter's Moon
…
| Title |
Zal Patera on Jupiter's Moon Io |
| Explanation |
The Galileo orbiter [ http://www.jpl.nasa.gov/galileo/mission.html ]'s flyby of Io [ http://www.seds.org/nineplanets/nineplanets/io.html ] last November captured an unusual part of Jupiter [ http://antwrp.gsfc.nasa.gov/apod/jupiter.html ]'s volcanic moon. From 26,000 kilometers away, Zal Patera [ http://wwwflag.wr.usgs.gov/USGSFlag/Space/nomen/append5.html ] was found to be a cauldron of flowing lava [ http://antwrp.gsfc.nasa.gov/apod/ap991220.html ], gaseous vents [ http://antwrp.gsfc.nasa.gov/apod/ap970428.html ], and tremendous peaks [ http://antwrp.gsfc.nasa.gov/apod/ap960805.html ]. Red lava can be seen in the above picture [ http://photojournal.jpl.nasa.gov/cgi-bin/PIAGenCatalogPage.pl?PIA02527 ] erupting along the base of the volcanic caldera, while cooling black lava lines the edge of a volcanic plateau. Shadow lengths indicate that the top of Zal Patera [ http://antwrp.gsfc.nasa.gov/apod/ap990513.html ] towers nearly 5 kilometers over Io [ http://galileo.jpl.nasa.gov/moons/io.html ]'s molten surface. Galileo zoomed past Io again last month [ http://galileo.jpl.nasa.gov/news/status/status000225.html ], and has begun beaming back images taken only 200 kilometers over Io's surface [ http://antwrp.gsfc.nasa.gov/apod/ap990920.html ]. |
|
Star Clouds over Arizona
| Title |
Star Clouds over Arizona |
| Explanation |
The clouds in the foreground are much different than the clouds in the background. In the foreground are a photogenic deck of Earth-based water clouds [ http://en.wikipedia.org/wiki/Clouds ]. The long exposure used to create the above photograph [ http://www.analemma.de/english/desrtsky.html ] makes the light from the left, reflected from Phoenix [ http://en.wikipedia.org/wiki/Phoenix%2C_Arizona ], Arizona [ http://en.wikipedia.org/wiki/Arizona ], USA [ http://www.cia.gov/cia/publications/factbook/geos/us.html ], appear like a sunset [ http://antwrp.gsfc.nasa.gov/apod/ap980526.html]. Far in the distance, however, are star clouds from the disk of our Milky Way Galaxy [ http://antwrp.gsfc.nasa.gov/apod/ap050605.html ]. Billions of stars like our Sun live there, circling our Galactic center every 200 million years. Contrast between the water clouds and the star clouds has been digitally enhanced [ http://www.astropix.com/HTML/J_DIGIT/ETHICS.HTM ]. Between the two, visible on the upper right, is the planet Jupiter [ http://antwrp.gsfc.nasa.gov/apod/ap050911.html ]. |
|
Free-Floating Planets In Ori
…
| Title |
Free-Floating Planets In Orion |
| Explanation |
This false-colour image [ http://www.ras.org.uk/press/pn00-04.htm ] of the young Trapezium star cluster in the Orion Nebula was made with an infrared camera [ http://www.jach.hawaii.edu/JACpublic/UKIRT/instruments/ ufti/ufti.html ] at wavelengths about twice as long as visible light. The infrared [ http://www.ipac.caltech.edu/Outreach/Edu/ discovery.html ] data are part of a sensitive survey of this nearby star forming region in which astronomers have identified [ http://xxx.lanl.gov/abs/astro-ph/0003061 ] over 100 extremely low mass objects -- candidates for elusive [ http://antwrp.gsfc.nasa.gov/apod/ap951204.html ] brown dwarf stars. Brown dwarfs [ http://www.amsci.org/amsci/articles/97articles/ martin.html ] are failed stars [ http://oposite.stsci.edu/pubinfo/background-text/ brdwarfs.txt ] with masses so low (about 8% of the Sun's) that they can not sustain nuclear hydrogen burning, a sun-like star's main energy source [ http://fusedweb.pppl.gov/default.html ]. While brown dwarfs are thought to be still massive enough to burn deuterium [ http://www.uilondon.org/D.HTM#deuterium ] for energy, thirteen of the low mass objects show evidence of lying below even the deuterium burning limit (about 1.3% of the Sun's [ http://nssdc.gsfc.nasa.gov/planetary/factsheet/ sunfact.html ] mass) falling in a range more commensurate with giant planets. These drifting, "free-floating planets" are perhaps as little as 8 times as massive as Jupiter [ http://nssdc.gsfc.nasa.gov/planetary/factsheet/ jupiterfact.html ] and likely formed along with the cluster stars a million or so years ago. They are detectable in the infrared because they are still hot from formation, but will eventually cool and fade. If the Trapezium [ http://seds.lpl.arizona.edu/messier/more/ m042_more.html ] is typical of young star clusters [ http://antwrp.gsfc.nasa.gov/apod/ap000227.html ], then the survey results suggest that brown dwarfs and free-floating planets may be fairly common, but there are not enough to solve the mystery of dark matter [ http://chandra.harvard.edu/xray_astro/dark_matter.html ] in the Universe. |
|
Jupiter and the Red Spots
| Title |
Jupiter and the Red Spots |
| Explanation |
Jupiter's Great Red Spot [ http://heritage.stsci.edu/1999/29/ index.html ] is a swirling storm seen for over 300 years, since the beginning of telescopic [ http://www.pacifier.com/~tpope/index.htm ] observations. But in February 2006, planetary imager Christopher Go [ http://jupiter.cstoneind.com/ ] noticed it had been joined by Red Spot Jr [ http://science.nasa.gov/headlines/y2006/ 02mar_redjr.htm ] - formed as smaller whitish oval-shaped [ http://antwrp.gsfc.nasa.gov/apod/ap981022.html ] storms merged and then developed the remarkable reddish hue. This sharp Hubble Space Telescope [ http://hubblesite.org/newscenter/newsdesk/archive/ releases/2006/19/ ] image showing the two salmon-colored Jovian storms was recorded [ http://hubblesite.org/newscenter/newsdesk/archive/releases/ 2006/19/fastfacts/ ] in April. About half the size of the original Red Spot, Red Spot Jr. [ http://www.redspotjr.com/ ] is similar in diameter to planet Earth. Seen here below and left of the ancient storm system, it trails the Great Red Spot by about an hour as the planet rotates from left to right. While astronomers still don't exactly understand why Jupiter's red spots are red [ http://antwrp.gsfc.nasa.gov/apod/ap960803.html ], they do think the appearance of Red Spot Jr. provides evidence for climate change on the Solar System's ruling gas giant [ http://antwrp.gsfc.nasa.gov/apod/ap030906.html ]. |
|
Venus, Moon, and Neighbors
| Title |
Venus, Moon, and Neighbors |
| Explanation |
Rising before the Sun on February 2nd, astrophotographer [ http://pages.prodigy.net/pam.orman/JoeGallery.html ] Joe Orman anticipated [ http://pages.prodigy.net/pam.orman/JoeAlmanac2000.html ] this apparition of the bright morning star [ http://ispec.scibernet.com/station/morn_star.html ] Venus near a lovely crescent Moon above a neighbor's house in suburban Phoenix, Arizona, USA. Fortunately, the alignment of bright planets and the Moon is one of the most inspiring sights in the night sky [ http://www.skypub.com/sights/skyevents/0004skyevents.html ] and one that is often easy to enjoy and share without any special equipment. Take tonight [ http://spacescience.com/headlines/y2000/ast30mar_1m.htm ], for example. Those blessed with clear skies can simply step outside near sunset and view a young crescent Moon very near three bright planets in the west Jupiter [ http://galileo.jpl.nasa.gov/ ], Mars [ http://mars.jpl.nasa.gov/mgs/ ], and Saturn [ http://www.jpl.nasa.gov/cassini/ ]. Jupiter will be the unmistakable brightest star near the Moon with a reddish Mars just to Jupiter's north and pale yellow Saturn directly above. Of course, these sky shows [ http://drumright.ossm.edu/astronomy/conjunctions.html ] create an evocative picture [ http://antwrp.gsfc.nasa.gov/apod/ap000310.html ] but the planets and Moon just appear to be near each other -- they are actually only approximately lined up and lie in widely separated orbits. Unfortunately, next month's highly publicized alignment of planets [ http://www.griffithobs.org/SkyAlignments.html ] on May 5th will be lost from view in the Sun's glare but such planetary alignments [ http://www.skypub.com/news/special/whypanic.html ] occur repeatedly and pose no danger [ http://www.badastronomy.com/bad/misc/planets.html ] to planet Earth. |
|
Saturn-Sized Worlds Discover
…
| Title |
Saturn-Sized Worlds Discovered |
| Explanation |
The last decade [ http://antwrp.gsfc.nasa.gov/apod/ap991229.html ] saw the profound discovery of many worlds [ http://origins.stsci.edu/news/2000/01/background.html ] beyond our solar system, but none analogs of our home planet Earth [ http://earthobservatory.nasa.gov/ ]. Exploiting precise observational techniques, astronomers inferred [ http://cannon.sfsu.edu/~gmarcy/planetsearch/planetsearch.html ] the presence of well over two dozen extrasolar planets [ http://cfa-www.harvard.edu/planets/ ], most nearly as massive as gas giant Jupiter or more, in close orbits around sun-like stars. Less massive planets must certainly exist, and yesterday preeminent planet-finders announced [ http://origins.stsci.edu/news/2000/01/ index.html ] the further detection of two more new worlds -- each a potentially smaller, saturn-sized planet. The parent [ http://antwrp.gsfc.nasa.gov/apod/ap990611.html ] suns are 79 Ceti (constellation Cetus [ http://www.astro.wisc.edu/~dolan/constellations/ constellations/Cetus.html ]), at a distance of 117 light-years, and HD46375 (constellation Monoceros [ http://www.astro.wisc.edu/~dolan/ constellations/constellations/Monoceros.html ]), 109 light-years away. With at least 70 percent the mass of Saturn, 79 Ceti's planet orbits [ http://origins.stsci.edu/news/2000/01/animations.html ] on average 32.5 million miles from the star compared to 93 million miles for the Earth-Sun distance [ http://antwrp.gsfc.nasa.gov/apod/ap981212.html ]. This arresting artist's vision depicts the newly discovered world with rings and moons, known characteristics of giant planets in our solar system. HD46375's planet is at least 80 percent Saturn's mass, orbiting only 3.8 million miles from its parent star. While Saturn's [ http://nssdc.gsfc.nasa.gov/planetary/ factsheet/saturnfact.html ] mass is only one third of Jupiter's [ http://nssdc.gsfc.nasa.gov/planetary/ factsheet/jupiterfact.html ], it is still about 100 times that of Earth, and dramatic discoveries in the search [ http://tpf.jpl.nasa.gov/ ] for smaller planets are still to come [ http://sim.jpl.nasa.gov/science/ planet.html ]. |
|
Europa: Ice Line
| Title |
Europa: Ice Line |
| Explanation |
This bright white swath cutting across the surface of icy Jovian moon Europa [ http://galileo.jpl.nasa.gov/moons/europa.html ] is known as Agenor Linea [ http://photojournal.jpl.nasa.gov/cgi-bin/ PIAGenCatalogPage.pl?PIA00877 ]. In all about 1000 kilometers long and 5 kilometers wide, only a section is pictured here [ http://photojournal.jpl.nasa.gov/cgi-bin/ PIAGenCatalogPage.pl?PIA01647 ] as part of a combined color and black and white image based on data from the Galileo spacecraft. Most linear features on Europa [ http://www.jpl.nasa.gov:80/galileo/europa/fact.html ] are dark in color but Agenor Linea is uniquely bright for unknown reasons. Also unknown is the origin of the reddish material along the sides. While these and other details of Europa's [ http://www.jpl.nasa.gov:80/galileo/news8.html ] surface formations remain mysterious, the general results of Galileo's exploration of Europa have supported the idea that an ocean of liquid water lies beneath [ http://photojournal.jpl.nasa.gov/ cgi-bin/PIAGenCatalogPage.pl?PIA01669 ] the cracked and frozen crust. An extraterrestrial liquid ocean [ http://science.nasa.gov/newhome/headlines/ast05mar98_1.htm ] holds out the tantalizing possibility [ http://quest.arc.nasa.gov/galileo/features/life.html ] of life. |
|
Planets Above The Clouds
| Title |
Planets Above The Clouds |
| Explanation |
Clouds scatter the faint orange rays of the setting sun [ http://antwrp.gsfc.nasa.gov/apod/ap000115.html ] in the foreground of this breathtaking photograph from the summit [ http://www.ifa.hawaii.edu/mko/mko.html ] of Mauna Kea, Hawaii [ http://antwrp.gsfc.nasa.gov/apod/ap980725.html ]. Taken on April 7th, this skyscape features a dramatic lunar and planetary alignment [ http://antwrp.gsfc.nasa.gov/apod/ap000406.html ]. An overexposed crescent moon [ http://antwrp.gsfc.nasa.gov/apod/ap991108.html ] dominates the celestial scene, but the bright "star" just below and to its right is Saturn [ http://www.jpl.nasa.gov/cassini/Kids/stories/ ] while further below Saturn is a close pairing of brilliant Jupiter [ http://antwrp.gsfc.nasa.gov/apod/ap000429.html ] and a fainter, yellowish Mars [ http://marsnt3.jpl.nasa.gov/education/students.html ]. Red giant star Aldebaran [ http://www.bo.astro.it/copernic/alde-eng.html ] is almost directly above the moon near the top of the image and the bright blue stars of the Pleiades cluster [ http://www.aao.gov.au/images.html/captions/uks018.html ] are visible about midway up and to the right of the moon-Aldebaran line. The good news is that planetary alignments [ http://www.skypub.com/news/special/whypanic.html ] like this one do not portend [ http://tech-two.mit.edu/Shakespeare/Tragedy/macbeth/ macbeth.html ] disasters, are relatively common, and can clearly make inspirational viewing for casual stargazers and astronomers alike. The bad [ http://www.badastronomy.com/bad/misc/planets.html ] news is that the world is not going to end because of the highly publicized planetary alignment [ http://www.griffithobs.org/SkyAlignments.html ] occurring tomorrow, May 5th -- so you probably will have to go to work [ http://www.nasa.gov/newsinfo/alignment.html ]! |
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Calderas And Cliffs Near Io'
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| Title |
Calderas And Cliffs Near Io's South Pole |
| Explanation |
Braving intense radiation [ http://www-spof.gsfc.nasa.gov/Education/Iradbelt.html ] belts [ http://www-spof.gsfc.nasa.gov/Education/wotherms.html ], the Galileo spacecraft once again [ http://galileo.jpl.nasa.gov/news/status/ status000222.html ] flew past the surface of Jupiter's moon Io [ http://sse.jpl.nasa.gov/features/planets/ jupiter/io.html ] (sounds like EYE-oh [ http://spaceplace.jpl.nasa.gov/gll_io_fact.htm ]) on February 22. Combining high resolution black and white images from that flyby with color data recorded last summer has resulted in this dramatic view [ http://photojournal.jpl.nasa.gov/ cgi-bin/PIAGenCatalogPage.pl?PIA02534 ] of a region near the volcanic moon's south pole. An active and alien landscape, the bright white areas are likely due to sulfur dioxide frost and seem to be concentrated near ridges and cliffs. The three ominous black spots, each about 6-12 miles across, are volcanic craters or calderas [ http://volcano.und.nodak.edu/vwdocs/vwlessons/lessons/ Hot_Spot/Hot_Spot10.html ] covered with recent dark lava. A sinuous channel connects the lower left caldera with a yellowish lava flow. Io is small, but its continuous [ http://www-a.jpl.nasa.gov/galileo/ganymede/ 122096.html ] activity is driven by the drastic tides [ http://co-ops.nos.noaa.gov/restles1.html ] induced by Jupiter [ http://sse.jpl.nasa.gov/features/planets/ jupiter/jupiter.html ] and the other Jovian moons. It is estimated that the resulting volcanism [ http://volcano.und.edu/vwdocs/planet_volcano/Io/ Overview.html ] completely resurfaces Io [ http://antwrp.gsfc.nasa.gov/apod/ap970321.html ] every million years. |
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Jupiter's Two Largest Storms
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| Title |
Jupiter's Two Largest Storms Nearly Collide |
| Explanation |
Two storms systems larger than Earth are nearly colliding right now on planet Jupiter [ http://www.nineplanets.org/jupiter.html ]. No one was sure what would happen, but so far both storms [ http://antwrp.gsfc.nasa.gov/apod/ap060505.html ] have survived. In the above false-color infrared image [ http://www.gemini.edu/jupiter06 ] taken last week by the Gemini Observatory [ http://antwrp.gsfc.nasa.gov/apod/ap030909.html ] in Hawaii [ http://antwrp.gsfc.nasa.gov/apod/ap020427.html ], the red spots appear white because their cloud tops tower above other clouds. Blue color represents lower clouds than white, while clouds colored red are the deepest. The smaller red spot, sometimes called Red Spot Jr. [ http://en.wikipedia.org/wiki/Oval_BA ] or just Oval BA, turned red earlier this year for reasons unknown. If both Jovian hurricanes [ http://en.wikipedia.org/wiki/Hurricane ] continue to survive, they will surely pass near each other again in a few years since they revolve around Jupiter at different rates. Astronomers will continue to monitor Red Spot Jr. [ http://antwrp.gsfc.nasa.gov/apod/ap060318.html ] closely, however, to see if it will remain red when it rotates away from the larger Great Red Spot [ http://en.wikipedia.org/wiki/Great_Red_Spot ]. |
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3D View Of Jupiter's Clouds
| Title |
3D View Of Jupiter's Clouds |
| Explanation |
Every day is a cloudy day on Jupiter [ http://nssdc.gsfc.nasa.gov/planetary/factsheet/ jupiterfact.html ], the Solar System's [ http://sse.jpl.nasa.gov/features/planets/planetsfeat.html ] reigning gas giant. This 3-dimensional visualization [ http://galileo.ivv.nasa.gov/europa/102997.html ] presents a simplified model view from between Jovian cloud decks based on imaging and spectral data recorded by the Galileo spacecraft [ http://eis.jpl.nasa.gov/~skientz/galileo/ ]. The separation between the cloud layers [ http://antwrp.gsfc.nasa.gov/apod/ap960803.html ] and the height variations have been exaggerated. The upper cloud layer is haze a few tens of miles thick. Heights in the lower cloud layers have been color coded, light bluish clouds are high and thin, reddish clouds are low, and white clouds are high and thick. Streaks in the lower layer suggestively lead to a dark blue area, a relatively clear, dry region [ http://antwrp.gsfc.nasa.gov/apod/ap970612.html ] similar to the site where Galileo's atmospheric probe [ http://ccf.arc.nasa.gov/galileo_probe/ ] made the first entry into a gas giant planet's atmosphere on December 7th, 1995. |
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Jupiter's Moons Thebe, Amalt
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| Title |
Jupiter's Moons Thebe, Amalthea, and Metis |
| Explanation |
The robot spacecraft Galileo [ http://eis.jpl.nasa.gov/~skientz/galileo/ ] in orbit around Jupiter [ http://www.seds.org/nineplanets/nineplanets/jupiter.html ] has recently photographed the inner moons of Jupiter in greater detail than ever before. These pictures [ http://www2.jpl.nasa.gov/files/images/captions/pia02531.txt ] of Thebe [ http://www.solarviews.com/eng/thebe.htm ], Amalthea [ http://www.solarviews.com/eng/amalthea.htm ], and Metis [ http://www.solarviews.com/eng/metis.htm ] are shown to scale, and reveal details as small as three kilometers across. Amalthea [ http://www.seds.org/nineplanets/nineplanets/amalthea.html#amalthea ], by contrast, has a total length of about 200 kilometers. The moons [ http://antwrp.gsfc.nasa.gov/apod/ap971127.html ] are composed mostly of ice, are much smaller than Jupiter's more famous Galilean satellites [ http://www.jpl.nasa.gov/galileo/moons/moons.html ] (Io [ http://www.seds.org/nineplanets/nineplanets/io.html ], Europa [ http://www.seds.org/nineplanets/nineplanets/europa.html ], Ganymede [ http://www.seds.org/nineplanets/nineplanets/ganymede.html ], and Callisto [ http://www.seds.org/nineplanets/nineplanets/callisto.html ]), and orbit between Io and Jupiter's rings [ http://antwrp.gsfc.nasa.gov/apod/ap980916.html ]. Thebe appears dominated by a huge impact crater [ http://gdcinfo.agg.emr.ca/toc.html?/crater/world_craters.html ] 40 kilometers across. Astronomers are uncertain of the origin of the unusual white gash at the bottom of Amalthea [ http://www.jpl.nasa.gov/galileo/amalthea/ ]. |
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Pleiades, Planets, And Hot P
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| 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. |
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Planets In The Sun
| Title |
Planets In The Sun |
| Explanation |
Today [ http://science.nasa.gov/headlines/y2000/ast02may_1.htm ], all five naked-eye planets [ http://www.seds.org/nineplanets/nineplanets/ ] (Mercury, Venus, Mars, Jupiter, Saturn) plus the Moon and the Sun [ http://helios.gsfc.nasa.gov/ sun.html ] will at least approximately line-up. As viewed [ http://drumright.ossm.edu/astronomy/conjunctions.html ] from planet Earth, they will be clustered within about 26 degrees, the closest alignment for all these celestial bodies [ http://science.nasa.gov/headlines/y2000/ ast30mar_1m.htm#alignments ] since February 1962, when there was a solar eclipse [ http://antwrp.gsfc.nasa.gov/apod/ap990818.html ]! Such planetary alignments [ http://www.griffithobs.org/SkyAlignments.html ] are not dangerous, except of course that the Sun might hurt your eyes when you look at it [ http://antwrp.gsfc.nasa.gov/apod/ap981212.html ]. So it might be easier [ http://sohowww.nascom.nasa.gov/hotshots/ ] to appreciate today's solar system [ http://space.jpl.nasa.gov/ ] spectacle if |
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Dog-Bone Shaped Asteroid 216
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| Title |
Dog-Bone Shaped Asteroid 216 Kleopatra |
| Explanation |
An asteroid [ http://www.seds.org/nineplanets/nineplanets/asteroids.html ] the size of New Jersey [ http://www.state.nj.us/ ] that orbits the Sun [ http://antwrp.gsfc.nasa.gov/apod/sun.html ] between Mars [ http://www.solarviews.com/eng/mars.htm ] and Jupiter [ http://www.jpl.nasa.gov/galileo/jupiter/jupiter.html ] has been discovered to have an unusual dog-bone shape. Asteroid 216 Kleopatra [ http://echo.jpl.nasa.gov/~ostro/kle/index.html ], recently mapped with Earth-based radar [ http://www-paoc.mit.edu/Radar_Lab/FAQ.html ], reflects radio waves [ http://imagers.gsfc.nasa.gov/ems/radio.html ] so well that astronomers speculate [ http://echo.jpl.nasa.gov/~ostro/kle/jpl_press_release ] it is composed mostly of metals such as nickel [ http://pearl1.lanl.gov/periodic/elements/28.html ] and iron [ http://www.webelements.com/webelements/scholar/elements/iron/key.html ]. The unusual shape and composition of 216 Kleopatra [ http://sc6.sc.eso.org/~fmarchis/Science/Kleopatra/ ] may derive from the central regions of a tremendous collision between larger asteroids [ http://antwrp.gsfc.nasa.gov/apod/asteroids.html ] billions of years ago. Kleopatra [ http://www.space.com/scienceastronomy/solarsystem/dogbone_asteroid_000505.html ] is not completely solid - its surface is loosely consolidated rubble, although its core may contain large solid-metal lodes. Kleopatra [ http://www.spaceref.com/news/viewnews.html?id=131 ] will never strike the Earth [ http://antwrp.gsfc.nasa.gov/apod/ap980313.html ], but it may one day serve as a valuable source of raw building materials. |
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A Halo Around the Moon
| Title |
A Halo Around the Moon |
| Explanation |
Have you ever seen a halo around the Moon? This fairly common sight occurs when high thin clouds [ http://ww2010.atmos.uiuc.edu/(Gh)/wwhlpr/cirrus.rxml?hret=/guides/mtr/opt/ice/halo/22.rxml ] containing millions of tiny ice crystals [ http://dspace.dial.pipex.com/lc/halo/crystals.htm ] cover much of the sky. Each ice crystal [ http://kristall.uni-mki.gwdg.de/homep1.htm ] acts like a miniature lens. Because most [ http://dspace.dial.pipex.com/lc/halo/xtalreal.htm ] of the crystals have a similar elongated hexagonal shape, light entering one crystal face and exiting through the opposing face refracts 22 degrees, which corresponds to the radius of the Moon Halo [ http://ww2010.atmos.uiuc.edu/(Gh)/guides/mtr/opt/ice/halo/22.rxml ]. A similar Sun Halo [ http://antwrp.gsfc.nasa.gov/apod/ap990823.html ] may be visible during the day. The town in the foreground of the above picture [ http://www.skylook.net/album/fenatm/fat3i.htm ] is San Sebastian [ http://www.donsnsn.es/icaste.htm ], Spain [ http://www.odci.gov/cia/publications/factbook/sp.html ]. The distant planet Jupiter [ http://antwrp.gsfc.nasa.gov/apod/jupiter.html ] appears by chance on the halo [ http://dspace.dial.pipex.com/lc/halo/halfeat.htm ]'s upper right. Exactly how ice-crystals form [ http://www.public.iastate.edu/~skrentz/ice_crystal.htm ] in clouds remains under investigation [ http://adsabs.harvard.edu/cgi-bin/nph-bib_query?bibcode=1995dri..rept.....H ]. |
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The Far Infrared Sky
| Title |
The Far Infrared Sky |
| Explanation |
Three major sources contribute to the far-infrared [ http://www.ipac.caltech.edu/Outreach/Edu/discovery.html ] sky [ http://antwrp.gsfc.nasa.gov/htmltest/jbonnell/www/multiw_sky.html ]: our Solar System [ http://www.seds.org/nineplanets/nineplanets/overview.html ], our Galaxy [ http://antwrp.gsfc.nasa.gov/apod/milky_way.html ], and our Universe [ http://antwrp.gsfc.nasa.gov/apod/ap000312.html ]. The above recently released image [ http://www.astro.ucla.edu/~wright/CIBR/images.html ], in representative colors, is the highest resolution projection yet created of the entire far-infrared sky [ http://www.astro.ucla.edu/~wright/old_new_cosmo.html#FIRB ] (60 - 240 microns) created from years of observations by the now-defunct robot spacecraft COBE [ http://space.gsfc.nasa.gov/astro/cobe/ ]. Our Solar System is evidenced most prominently by the S-shaped blue sash called zodiacal light [ http://antwrp.gsfc.nasa.gov/apod/ap990613.html ], created by small pieces of rock and dust [ http://antwrp.gsfc.nasa.gov/apod/ap981121.html ] orbiting between the Sun [ http://antwrp.gsfc.nasa.gov/apod/sun.html ] and Jupiter [ http://www.jpl.nasa.gov/galileo/jupiter/jupiter.html ]. The disk of our Galaxy [ http://adc.gsfc.nasa.gov/mw/milkyway.html ] is evidenced most prominently by the thin band of light-emitting dust [ http://antwrp.gsfc.nasa.gov/apod/ap990509.html ] that crosses the middle of the image. Clouds and filaments of dust in our Milky Way [ http://antwrp.gsfc.nasa.gov/apod/ap971229.html ] also make intricate patterns pervading most of the sky. Close inspection of similar images reveal [ http://adsabs.harvard.edu/cgi-bin/nph-bib_query?bibcode=1998ApJ...500..525S ] that the background is not completely dark, indicating that our Universe itself provides a diffuse glow [ http://antwrp.gsfc.nasa.gov/apod/ap980121.html ], created by dust left over from the star formation throughout the Universe [ http://adsabs.harvard.edu/cgi-bin/nph-bib_query?bibcode=1998ApJ...508..106D ]. |
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Ganymede: The Largest Moon i
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| Title |
Ganymede: The Largest Moon in the Solar System |
| Explanation |
If Ganymede orbited the Sun, it would be considered a planet. The reason is that Jupiter [ http://galileo.jpl.nasa.gov/jupiter/jupiter.html ]'s moon Ganymede [ http://www.seds.org/nineplanets/nineplanets/ganymede.html ] is not only the largest moon in the Solar System [ http://www.seds.org/nineplanets/nineplanets/datamax.html ], it is larger than planets Mercury [ http://www.seds.org/nineplanets/nineplanets/mercury.html ] and Pluto [ http://dosxx.colorado.edu/plutohome.html ]. The robot spacecraft Galileo [ http://www.jpl.nasa.gov/galileo/overview.html ] currently orbiting Jupiter [ http://www.seds.org/nineplanets/nineplanets/jupiter.html ] has been able to zoom by Ganymede [ http://www.solarviews.com/eng/ganymede.htm ] several times and snap many close-up pictures. Ganymede, shown above [ http://photojournal.jpl.nasa.gov/cgi-bin/PIAGenCatalogPage.pl?PIA00716 ] in its natural colors, sports a large oval dark region known as Galileo Regio [ http://www.jpl.nasa.gov/galileo/ganymede/121896.html ]. In general, the dark regions on Ganymede [ http://sse.jpl.nasa.gov/features/planets/jupiter/ganymede.html ] are heavily cratered, implying they are very old, while the light regions are younger and dominated by unusual grooves [ http://antwrp.gsfc.nasa.gov/apod/ap960711.html ]. The origin of the grooves is still under investigation [ http://adsabs.harvard.edu/cgi-bin/nph-bib_query?bibcode=1998Icar..135..317P ]. |
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Ceres: Asteroid or Planet?
| Title |
Ceres: Asteroid or Planet? |
| Explanation |
Is Ceres [ http://en.wikipedia.org/wiki/Ceres_%28asteroid%29 ] an asteroid [ http://www.nineplanets.org/asteroids.html ] or a planet? Although a trivial designation to some, the recent suggestion by the Planet Definition Committee [ http://www.iau2006.org/mirror/www.iau.org/iau0601/iau0601_committee.html ] of the International Astronomical Union [ http://www.iau2006.org/mirror/www.iau.org/NEWS.55.0.html ] would have Ceres reclassified from asteroid to planet. A change in taxonomy might lead to more notoriety for the frequently overlooked world. Ceres [ http://www.pantheon.org/articles/c/ceres.html ], at about 1000 kilometers across, is the largest object in the main asteroid belt [ http://www.solstation.com/stars/asteroid.htm ] between Mars and Jupiter. Under the newly proposed criteria [ http://www.iau2006.org/mirror/www.iau.org/iau0601/iau0601_release.html ], Ceres would qualify as a planet because it is nearly spherical and sufficiently distant from other planets. Pictured above [ http://hubblesite.org/newscenter/newsdesk/archive/releases/2005/27/image/a ] is the best picture yet of Ceres, taken by the Hubble Space Telescope [ http://antwrp.gsfc.nasa.gov/apod/ap010806.html ] as part of a series of exposures ending in 2004 January. Currently, NASA's Dawn mission [ http://dawn.jpl.nasa.gov/ ] is scheduled to launch in 2007 June to explore Ceres and Vesta [ http://antwrp.gsfc.nasa.gov/apod/ap060820.html ], regardless of their future designations. |
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Up Close to Jupiter's Moon I
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| Title |
Up Close to Jupiter's Moon Io |
| Explanation |
Above is the highest resolution photograph [ http://photojournal.jpl.nasa.gov/cgi-bin/PIAGenCatalogPage.pl?PIA02556 ] yet taken of the Solar System [ http://www.seds.org/nineplanets/nineplanets/overview.html ]'s strangest moon. The surface of Jupiter [ http://www.solarviews.com/eng/jupiter.htm ]'s moon Io [ http://galileo.jpl.nasa.gov/moons/io.html ] is home to violent volcanoes [ http://antwrp.gsfc.nasa.gov/apod/ap000606.html ] that are so active they turn the entire moon inside out. The above photograph [ http://photojournal.jpl.nasa.gov/cgi-bin/PIAGenCatalogPage.pl?PIA02556 ] shows a region four kilometers across and resolves features only five meters [ http://www.twenj.com/measures.htm ] across. Many revealed details are not well understood. In general, the bright areas are higher terrain than the darker areas, but some areas of the surface appear eroded [ http://www.qub.ac.uk/geosci/teaching/postgrad/workshop1/erosion1.html ] by an unknown process. Although the parts of Io's surface [ http://antwrp.gsfc.nasa.gov/apod/ap970321.html ] near erupting volcanoes are hot enough to melt rock, most of Io [ http://antwrp.gsfc.nasa.gov/apod/ap990920.html ] has cooled well below the freezing point of water [ http://www.nyu.edu/pages/mathmol/modules/water/info_water.html ]. The robot spacecraft Galileo [ http://www.jpl.nasa.gov/galileo/overview.html ] during its most recent flyby [ http://galileo.jpl.nasa.gov/news/release/press000531.html ] of Io [ http://www.seds.org/nineplanets/nineplanets/io.html ] took the above image in 2000 February. |
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A Continuous Eruption on Jup
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| Title |
A Continuous Eruption on Jupiter's Moon Io |
| Explanation |
A volcano on Jupiter's moon Io [ http://www.seds.org/nineplanets/nineplanets/io.html ] has been photographed recently during an ongoing eruption. Hot glowing lava is visible on the left on this representative-color image [ http://photojournal.jpl.nasa.gov/cgi-bin/PIAGenCatalogPage.pl?PIA02550 ]. A glowing landscape of plateaus and valleys covered in sulfur [ http://pearl1.lanl.gov/periodic/elements/16.html ] and silicate rock [ http://windows.ivv.nasa.gov/cgi-bin/tour_def/glossary/silicate_rock.html ] surrounds the active volcano [ http://volcano.und.nodak.edu/vwdocs/planet_volcano/Io/Overview.html ]. Many features including several of the dark spots [ http://antwrp.gsfc.nasa.gov/apod/ap971110.html ] have evolved between February 2000, when the robot spacecraft Galileo [ http://www.jpl.nasa.gov/galileo/spacecraft.html ] currently orbiting Jupiter [ http://www.seds.org/nineplanets/nineplanets/jupiter.html ] took this picture, and November 1999. Io [ http://cass.jsc.nasa.gov/pub/research/outerp/io.html ] is slightly larger than Earth's Moon [ http://antwrp.gsfc.nasa.gov/apod/ap991108.html ] and is the closest large moon to Jupiter [ http://galileo.jpl.nasa.gov/jupiter/jupiter.html ]. The above image [ http://photojournal.jpl.nasa.gov/cgi-bin/PIAGenCatalogPage.pl?PIA02550 ] shows a region about 250 kilometers across. How the internal structure of Io [ http://adsabs.harvard.edu/cgi-bin/nph-bib_query?bibcode=1990Icar...85..309R ] creates these active volcanoes [ http://antwrp.gsfc.nasa.gov/apod/ap961027.html ] remains under investigation. |
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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 ]. |
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Crater On Ice
| Title |
Crater On Ice |
| Explanation |
Impact craters are common on Earth's moon [ http://antwrp.gsfc.nasa.gov/apod/ap990326.html ] but on Jupiter's large ice moon Europa [ http://sse.jpl.nasa.gov/features/planets/jupiter/ europa.html ], they are very rare. Over time, both bodies have been subjected to an intense pounding [ http://antwrp.gsfc.nasa.gov/apod/ap990610.html ] by the solar system's formative debris [ http://www.jhuapl.edu/public/pr/000530.htm ], but geological activity on Europa's surface seems to have erased most of these impact scars. This false-color infrared image [ http://photojournal.jpl.nasa.gov/cgi-bin/ PIAGenCatalogPage.pl?PIA02561 ] from the Galileo spacecraft's NIMS instrument [ http://jumpy.igpp.ucla.edu/~nims/ ] shows a newly discovered crater on Europa as a light red ring feature near center surrounding a dark core. For scale, the dark core is about 29 kilometers in diameter. Only seven comparably [ http://antwrp.gsfc.nasa.gov/apod/ap970417.html ] large craters have now been identified on Europa's surface. Red colors in the image represent a relatively pure water ice [ http://www.glacier.rice.edu/invitation/1_icetypes.html ] composition while blue colors indicate that other minerals are present. The crater's central dark area may contain the remnants of the impacting body. The icy crust of Europa [ http://galileo.jpl.nasa.gov/moons/europa.html ] is of great interest, as evidence mounts [ http://galileo.jpl.nasa.gov/news/release/ press000110.html ] that it covers an ocean of liquid water, possibly providing suitable conditions for life. |
|
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. |
|
LP 944-20: A Failed Star Fla
…
| Title |
LP 944-20: A Failed Star Flares |
| Explanation |
The tiny spot circled on the right actually represents a big astronomical discovery [ http://chandra.harvard.edu/press/00_releases/ press_071100.html ] -- the first detected flare from a failed star. Failed stars, termed brown dwarfs [ http://chandra.harvard.edu/xray_sources/ browndwarf_fg.html ] in astronomers' parlance [ http://oposite.stsci.edu/pubinfo/background-text/ brdwarfs.txt ], are too low in mass to ignite nuclear hydrogen burning in their cores, yet still shine feebly as the energy from their gravitational collapse is converted to heat and light. In fact, the dim brown dwarf [ http://www.amsci.org/amsci/articles/97articles/ martin.html ] cataloged as LP944-20 is estimated to have only 6 percent the mass of the Sun (60 times the mass of Jupiter) and one-tenth the Sun's diameter. A mere 16 light-years distant in the southern constellation Fornax it is well studied [ http://www.eso.org/outreach/press-rel/pr-1997/ pr-07-97.html ], but this failed star recently startled astronomers [ http://xxx.lanl.gov/abs/astro-ph/0005559 ] by producing a flare visible at x-ray energies [ http://imagine.gsfc.nasa.gov/docs/science/know_l1/ history1_xray.html ]. The above Chandra X-ray Observatory [ http://chandra.harvard.edu/ ] images of the LP944-20 [ http://chandra.harvard.edu/photo/cycle1/1054/ lp94420_hand.html ] star field were recorded in December 1999. Showing nothing (left) for the first nine hours, the brown dwarf generated a significant x-ray flare during the final hours of the observation. How did a failed star produced such a high-energy flare [ http://antwrp.gsfc.nasa.gov/apod/ap000608.html ]? Magnetic fields twisted and broken by turbulent motions near the surface of the brown dwarf may be the culprit. Difficult [ http://antwrp.gsfc.nasa.gov/apod/ap990324.html ] to detect because they are otherwise faint, brown dwarf stars are believed to be common [ http://www.amsci.org/amsci/articles/97articles/ mhowmany.html ] throughout the galaxy. |
|
Other Worlds and HD 38529
| Title |
Other Worlds and HD 38529 |
| Explanation |
After the latest round of discovery announcements [ http://www.iau.org/ga24press/ ], the list of known worlds of distant suns [ http://www.spaceart.org/lcook/extrasol.html ] has grown to 50 [ http://www.spaceref.com/news/viewnews.html?id=200 ]. While extrasolar planet [ http://exoplanets.org/ ] discoveries are [ http://obswww.unige.ch/~udry/planet/planet.html ] sure to continue, none - so far [ http://sim.jpl.nasa.gov/ ] - points clearly to another planetary system like our own [ http://antwrp.gsfc.nasa.gov/apod/ap991229.html ]. Take, for example, the newly discovered parent [ http://antwrp.gsfc.nasa.gov/apod/ap990611.html ] star HD38529 [ http://www.obspm.fr/encycl/HD38529.html ]. Shining in Earth's night sky at 6th magnitude, this sun-like star lies 137 light-years away in the constellation Orion [ http://aibn47.astro.uni-bonn.de/~gallery/constellations/orion/ main.html ]. Like most of the known extrasolar planets [ http://www.obspm.fr/encycl/encycl.html ], HD38529's planet was discovered by detecting the telltale Doppler wobble [ http://exoplanets.org/doppler.html ] in the parent star's spectrum. The data reveal that this planet orbits once every 14.3 days at an average of only 0.13 times the Earth-Sun distance and has a minimum of 0.77 Jupiter masses (about 240 Earth masses). There is even evidence [ http://www.iau.org/ga24press/pr000807_3.html#1 ] in the wobble data that HD38529, and other stars with one known planet have additional massive planets orbiting them. In this dramatic artist's vision, HD38529 and its newfound world are viewed from the moon of another massive ringed planet [ http://antwrp.gsfc.nasa.gov/apod/ap000330.html ] orbiting farther out. The ringed planet's moon is imagined to have a thin atmosphere and a surface covered with icy sheets and ridges similar to those found on Jupiter's moon Europa [ http://galileo.jpl.nasa.gov/moons/europa.html ]. |
|
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. |
|
Nearby Star Episilon Eridani
…
| Title |
Nearby Star Episilon Eridani Has a Planet |
| Explanation |
A planet has been found orbiting a Sun-like star only 10 light-years [ http://einstein.stcloudstate.edu/Dome/constellns/lightyear.html ] away. No direct picture of the planet was taken - the planet was discovered [ http://stardate.utexas.edu/pr/pages/20000807.html ] by the gravitational [ http://exoplanets.org/wobl.html ] wobble [ http://instruct1.cit.cornell.edu/courses/astro101/java/binary/binary.htm ] it created on its parent star, Epsilon Eridani [ http://www.solstation.com/stars/eps-erid.htm ]. The discovery [ http://www.spaceref.com/news/viewnews.html?id=197 ] marks the closest [ http://antwrp.gsfc.nasa.gov/apod/ap961019.html ] Sun-like star yet found [ http://exoplanets.org/planet_table.html ] to house an extra-solar planet [ http://astron.berkeley.edu/~gmarcy/sciam.html ]. Pictured above [ http://www.astro.uiuc.edu/~kaler/sow/eri-p.html ], the star Epsilon Eridani [ http://sol.stsci.edu/~kalas/disksite/pages/epseri850.html ] is visible near the belt of Orion [ http://antwrp.gsfc.nasa.gov/apod/ap960418.html ] to the unaided eye. The detected planet [ http://news.bbc.co.uk/hi/english/sci/tech/newsid_865000/865365.stm ] is thought to have a mass like Jupiter [ http://www.seds.org/nineplanets/nineplanets/jupiter.html ] but orbit slightly closer in. The elliptical [ http://www-groups.dcs.st-and.ac.uk/~history/Curves/Ellipse.html ] nature of the planet's orbit raises questions about whether the nearly circular orbits of planets in our own Solar System [ http://www.seds.org/nineplanets/nineplanets/overview.html ] are relatively uncommon. It is unknown whether other planets exist around Epsilon Eridani [ http://adsabs.harvard.edu/cgi-bin/nph-bib_query?bibcode=1998ApJ...506L.133G ]. |
|
Comet LINEAR Breaks Up
| Title |
Comet LINEAR Breaks Up |
| Explanation |
Unexpectedly, Comet LINEAR is breaking up [ http://meteors.com/cometlinear/update.html ]. In retrospect, clues of its demise have been surfacing all month as the new comet [ http://antwrp.gsfc.nasa.gov/apod/ap000727.html ] has been approaching the Sun [ http://www.seds.org/nineplanets/nineplanets/sol.html ] and brightening [ http://spacescience.com/headlines/y2000/ast28jul_1m.htm ] with dramatic flares. Above [ http://oposite.stsci.edu/pubinfo/PR/2000/26/index.html ], the Hubble Space Telescope [ http://antwrp.gsfc.nasa.gov/apod/ap970306.html ] captured Comet C/1999 S4 LINEAR [ http://antwrp.gsfc.nasa.gov/apod/ap000704.html ] early this month blowing off a large piece of its crust. Recent speculation [ http://www.ing.iac.es/PR/press/ing200.html ] holds that the nucleus completely disrupted [ http://spaceweather.com/meteoroutlook/iauc7467.html ] on or about July 24. If true, the elongated train [ http://antwrp.gsfc.nasa.gov/apod/ap990814.html ] of material should continue to ablate and orbit the Sun, but may now fade much more quickly. The break up of a bright comet [ http://www.solarviews.com/eng/comet.htm ] is unusual but not unprecedented, as Comet Shoemaker-Levy 9 [ http://antwrp.gsfc.nasa.gov/apod/ap980804.html ] broke up before it struck Jupiter [ http://www.seds.org/nineplanets/nineplanets/jupiter.html ] in 1994, and Comet Bennett [ http://meteors.com/cometlinear/update.html ] broke apart as it neared the Sun in 1974. Future observations will tell if Comet LINEAR [ http://antwrp.gsfc.nasa.gov/apod/ap000710.html ]'s first trip into the inner Solar System [ http://www.seds.org/nineplanets/nineplanets/overview.html ] is its last. |
|
Folding Europa
| Title |
Folding Europa |
| Explanation |
Astypalaea Linea [ http://wwwflag.wr.usgs.gov/USGSFlag/Space/nomen/jupiter/ euroTOC.html ] on Jovian [ http://cfa-www.harvard.edu/iau/pressinfo/S1999J1.html ] ice moon Europa [ http://www.seds.org/nineplanets/nineplanets/ europa.html ] is the broad smooth region running through these images [ http://photojournal.jpl.nasa.gov/cgi-bin/ PIAGenCatalogPage.pl?PIA02960 ] recorded by the Galileo spacecraft in 1998. The pictures are different computer processed versions of the same mosaic -- on the left, small scale details have been enhanced while on the right, large scale features are emphasized. In both versions, the bold criss-crossing ridges [ http://antwrp.gsfc.nasa.gov/apod/ap981215.html ] believed to result from the upwelling of new material through cracks in the surface ice are apparent. But more easily seen on the right are recently recognized [ http://www.jhuapl.edu/public/pr/000810.htm ] gentle rises and dips, about 15 kilometers across, which likely formed as the icy surface was compressed by the addition of the new material. Further evidence [ http://adsabs.harvard.edu/cgi-bin/nph-bib_query? bibcode=2000LPI....31.1182P&db_key=AST&high=3899d8d98211881 ] that stress is folding Europa's [ http://galileo.jpl.nasa.gov/moons/europa.html ] surface is offered by the presence of smaller cracks and wrinkles more easily seen on the left. These span the width of the broad swells suggestive of anticlines and synclines [ http://www.educ.uvic.ca/Faculty/jtinney/earth%20science/ ESMain.html#fold ] familiar to geologists on planet Earth [ http://antwrp.gsfc.nasa.gov/apod/ap000420.html ]. Though ice covered [ http://spacescience.com/headlines/y2000/ ast22aug_1.htm ], the surface of Europa is thought to be geologically active, riding over a substantial ocean [ http://adsabs.harvard.edu/cgi-bin/nph-bib_query? bibcode=1998Natur.391..363C&db_key=AST&high=3899d8d98211557 ] of liquid water. |
|
Eros At Sunset
| Title |
Eros At Sunset |
| Explanation |
Gleaming in the rays of the setting sun, boulders litter the rugged surface of asteroid 433 Eros [ http://near.jhuapl.edu/eros/ ]. The brightest boulder, at the edge of the large, shadowy crater near this picture's bottom center, is about 30 meters (100 feet) across. In orbit around Eros since February 2000, the NEAR Shoemaker [ http://near.jhuapl.edu/NEAR/ ] spacecraft's camera recorded the dramatic view [ http://near.jhuapl.edu/NEAR/iod/20000821/index.html ] earlier this month from an altitude of about 50 kilometers. Eros itself orbits [ http://www.fwkc.com/encyclopedia/low/articles/o/ o018000416f.html ] the Sun with a perihelion [ http://imagine.gsfc.nasa.gov/docs/ dictionary.html#perihelion ] of 1.13 Astronomical Units [ http://imagine.gsfc.nasa.gov/docs/ask_astro/ answers/980122b.html ] (AU) and aphelion [ http://imagine.gsfc.nasa.gov/docs/ dictionary.html#aphelion ] of 1.78 AU. Part of a class of near-Earth asteroids [ http://neo.jpl.nasa.gov/neo.html ], it spends much of its time between the orbits of Mars (at 1.5 AU) and Earth (at 1 AU) ... but it wasn't always that way. Eros and other near-Earth asteroids [ http://neo.planetary.org/ABCsOfNEOs/index.html ] originally orbited in the main asteroid belt [ http://seds.lpl.arizona.edu/nineplanets/nineplanets/ asteroids.html ], between Jupiter [ http://galileo.jpl.nasa.gov/jupiter/jupiter.html ] and Mars [ http://nssdc.gsfc.nasa.gov/planetary/factsheet/ marsfact.html ]. Over time, the gravitational influence of Jupiter and other planets perturbed their orbits sending them on trajectories closer [ http://antwrp.gsfc.nasa.gov/apod/ap000226.html ] to Earth. |
|
Mount Megantic Magnetic Stor
…
| Title |
Mount Megantic Magnetic Storm |
| Explanation |
Plasma from the Sun and debris from a comet both collided with planet Earth last Saturday morning triggering magnetic storms [ http://www.sec.noaa.gov/NOAAscales/ ] and a meteor shower in a dazzling atmospheric spectacle [ http://spacescience.com/headlines/y2000/ ast14aug_1.htm ]. The debris stream from comet Swift-Tuttle is anticipated [ http://antwrp.gsfc.nasa.gov/apod/ap000812.html ] yearly, and many skygazers [ http://www.imo.net/news/news.html ] already planned to watch the peak of the annual Perseids [ http://comets.amsmeteors.org/meteors/showers/ perseids.html ] meteor shower in the dark hours of August 11/12. But the simultaneous, widely reported [ http://www.globaldialog.com/~jrummel/Aurora/ Aurora.html ] auroras were [ http://www.infowest.com/personal/s/schmutz/ aurora.HTML ] triggered by the chance arrival of something much less predictable -- a solar coronal mass ejection [ http://science.nasa.gov/ssl/pad/solar/ cmes.htm ]. This massive bubble of energetic plasma was seen leaving the active Sun's surface on August 9, just in time to travel to Earth and disrupt the planet's magnetic field [ http://www-spof.gsfc.nasa.gov/Education/ Intro.html ] triggering extensive auroras [ http://antwrp.gsfc.nasa.gov/cgi-bin/apod/ apod_ts?aurora ] during the meteor shower's peak! Inspired by the cosmic light show, Sebastien Gauthier photographed the [ http://www.geocities.com/CapeCanaveral/Station/3622/ AlbumPhotoAstronomie/AlbumAstronomie3.htm ] colorful auroral displays above the dramatic dome of the Mount-Megantic [ http://astrolab.interlinx.qc.ca/ ] Popular Observatory [ http://astrolab.interlinx.qc.ca/Obs_pop/ OPMM/ob_pop_choix.htm ] in southern Quebec, Canada. Bright Jupiter and giant star Aldebaran can be seen peering through [ http://antwrp.gsfc.nasa.gov/apod/ap000504.html ] the shimmering northern lights at the upper right. |
|
The Hubble SWEEPS Field
| Title |
The Hubble SWEEPS Field |
| Explanation |
This crowded star field [ http://hubblesite.org/newscenter/newsdesk/archive/ releases/2006/34/ ] towards the center of our Milky Way Galaxy turns out to be a great place to search for planets beyond [ http://www.alienearths.org/online/ starandplanetformation/planetfamilies.php ] our solar system. In fact, repeatedly imaging about 180,000 stars in the field [ http://hubblesite.org/newscenter/newsdesk/archive/ releases/2006/34/fastfacts/ ] over a one week period, the Hubble Space Telescope enabled astronomers to conduct the Sagittarius Window Eclipsing Extrasolar Planet Search (SWEEPS). Their search looked for brief, periodic dips in brightness caused as a large planet eclipses [ http://antwrp.gsfc.nasa.gov/apod/ap991115.html ] or transits its parent star. Since chances [ http://imgsrc.hubblesite.org/hu/db/2006/34/images/g/ formats/web_print.jpg ] of seeing such an eclipse are slim, it was a definite advantage to examine as many stars as possible. In the end, SWEEPS astronomers found [ http://arxiv.org/abs/astro-ph/0610098 ] 16 candidate stars (green circles identify 11 in this cropped picture) that are likely closely orbited by large Jupiter-sized planets with periods of a few days or less. Large planets orbiting so close to their stars are termed hot Jupiters [ http://www.spitzer.caltech.edu/Media/releases/ ssc2006-18/release.shtml ]. Kepler [ http://www.kepler.arc.nasa.gov/ ], a future NASA mission, is intended to extend the transit technique to search for Earth-sized planets [ http://planetquest.jpl.nasa.gov/index.cfm ]. |
|
Approaching Jupiter
| Title |
Approaching Jupiter |
| Explanation |
In 1979 the Voyager 1 spacecraft [ http://vraptor.jpl.nasa.gov/voyager/voyager_fs.html ] compiled this view as it approached the gas giant Jupiter [ http://www.seds.org/nineplanets/nineplanets/jupiter.html ]. Snapping a picture every time the Great Red Spot [ http://antwrp.gsfc.nasa.gov/apod/ap960827.html ] was properly aligned, the above time-lapse sequence [ http://photojournal.jpl.nasa.gov/cgi-bin/PIAGenCatalogPage.pl?PIA02259 ] shows not only spot [ http://www.gfdl.gov/~gw/ ] rotation but also the swirling of neighboring clouds [ http://antwrp.gsfc.nasa.gov/apod/ap000429.html ]. Since Jupiter [ http://www.solarviews.com/eng/jupiter.htm ] takes about 10 hours to rotate, this short sequence actually covers several days. Voyager 1 shot past Jupiter [ http://antwrp.gsfc.nasa.gov/apod/jupiter.html ] rapidly taking pictures on which many discoveries [ http://www.solarviews.com/eng/vgrjup.htm ] would be made, including previously unknown cloud patterns [ http://antwrp.gsfc.nasa.gov/apod/ap970920.html ], rings [ http://antwrp.gsfc.nasa.gov/apod/ap980916.html ], moons [ http://www.seds.org/nineplanets/nineplanets/amalthea.html#adrastea ], and active volcanoes [ http://antwrp.gsfc.nasa.gov/apod/ap960805.html ] on Jupiter's moon Io [ http://www.jpl.nasa.gov/galileo/moons/io.html ]. Voyager is moving so fast that it will one day leave [ http://antwrp.gsfc.nasa.gov/apod/ap980620.html ] our Solar System [ http://www.seds.org/nineplanets/nineplanets/overview.html ]. |
|
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. |
|
Children of the Sun
| Title |
Children of the Sun |
| Explanation |
For a moment [ http://photojournal.jpl.nasa.gov/index.html ], planets Jupiter [ http://kids.nineplanets.org/jupiter.htm ], Venus [ http://kids.nineplanets.org/venus.htm ], Mars [ http://kids.nineplanets.org/mars.htm ], and Mercury [ http://kids.nineplanets.org/mercury.htm ] all posed near their parent star in this Sun-centered view, recorded on November 11. The picture, from a coronograph onboard the space-based SOlar Heliospheric Observatory [ http://sohowww.nascom.nasa.gov/ ], spans 15 degrees with the Sun's size and position indicated by the white circle. Background stars are also visible as the otherwise overwhelming sunlight is blocked by the coronograph's [ http://lasco-www.nrl.navy.mil/index.php?p=content/ about_lasco ] occulting disk. But the planets themselves, in particular Jupiter and Venus, are still bright enough to cause significant horizontal streaks in the image. Mercury is actually moving most rapidly (left to right) through the field and days earlier [ http://sohowww.nascom.nasa.gov/hotshots/2006_11_06/ ] was seen to cross in front [ http://www.spaceweather.com/eclipses/gallery_08nov06.htm ] of the solar disk. So what's that bright double star to the left of Mars? Zubenelgenubi [ http://antwrp.gsfc.nasa.gov/apod/ap040514.html ], of course. |
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