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VEGA of Goddard Space Flight Center (GSFC) and Arizona
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Asteroid 2002 NY40
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Asteroid 2002 NY40 |
| Explanation |
Asteroid 2002 NY40 [ http://science.nasa.gov/headlines/y2002/ 30jul_ny40.htm ] will fly by planet Earth early in the morning August 18 Universal Time (late in the evening August 17 Eastern Daylight Time). Approaching to within [ http://neo.jpl.nasa.gov/ ] about 530,000 kilometers or 1.3 times the Earth-Moon distance 2002 NY40 [ http://neo.jpl.nasa.gov/cgi-bin/db?name=2002+NY40 ] will definitely not be close enough to pose any danger of collision. But it will be close enough and just bright enough for experienced skygazers to see this 800 meter wide space rock [ http://seds.lpl.arizona.edu/nineplanets/nineplanets/ asteroids.html ] in a small telescope or binoculars as it glides quickly through northern skies [ http://science.nasa.gov/headlines/y2002/images/ny40/ skymap_ut.gif ] past the bright star Vega. It will also be close enough to ping with radar [ http://echo.jpl.nasa.gov/ ], and asteroid hunters using the large Arecibo radio telescope [ http://antwrp.gsfc.nasa.gov/apod/ap981129.html ] in Puerto Rico expect to determine the three dimensional outline of 2002 NY40. Similar investigations of other near Earth [ http://antwrp.gsfc.nasa.gov/apod/ap970120.html ] asteroids have revealed some surprising shapes [ http://antwrp.gsfc.nasa.gov/apod/ap000510.html ]. In this five minute time exposure, recorded at Cerro Tololo [ http://www.ctio.noao.edu/ ] Inter-American Observatory on August 14, 2002 NY40 shows itself as a long smudge as it moves against a background of faint stars in the constellation Aquarius [ http://www.windows.ucar.edu/tour/link=/the_universe/ Constellations/aquarius.html ]. |
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HR 4796A: Not Saturn
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HR 4796A: Not Saturn |
| Explanation |
These are not false-color renderings of the latest observations of Saturn's magnificent rings [ http://antwrp.gsfc.nasa.gov/apod/ap980424.html ]. Instead, the panels show a strikingly similar system on a much larger scale - a ring around the young, Vega-like star, HR 4796A [ http://oposite.stsci.edu/pubinfo/pr/1999/03/b.html ], located about 200 light-years from Earth. Probably composed of dusty debris ground from colliding planetesimals, this ring is confined to a zone less than 17 AU wide (1 AU equals the Earth-Sun distance) and girdles the star at a radius of about 70 AU, roughly twice the orbital radius of Neptune. In analogy with the relationship of Saturn's rings and moons [ http://ringmaster.arc.nasa.gov/reference/abstracts/cuzzi1984_01.html ], this circumstellar ring could be held in place by forces due to planets - shepherding planetary bodies or the gravitational influence of larger planets orbiting closer to the parent star. In any event, because the ring would not survive long without something to keep it there, astronomers consider its presence strong evidence for unseen planetary bodies [ http://www.generation.net/~mariob/astro/xtrasol.htm ] around HR 4796A. The top panels show the false-color images [ http://nicmosis.as.arizona.edu:8000/AAS99/hr4796_postrev5.ps ] at two infrared wavelengths from the Hubble Space Telescope's NICMOS instrument [ http://nicmos.as.arizona.edu/ ], and the bottom panels trace the corresponding image contours. At the center of each, the overwhelming light of HR 4796A has been masked to reveal the fainter circumstellar ring. |
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