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Leonids from Orbit
| Title |
Leonids from Orbit |
| Explanation |
Here is what a meteor shower [ http://www.imo.net/calendar/cal00.html ] looks like from orbit. During the peak of the 1997 Leonid Meteor Shower [ http://www-space.arc.nasa.gov/~leonid/1997.html ], the MSX satellite [ http://scies.plh.af.mil:8600 ] imaged from above 29 meteors over a 48 minute period entering the Earth's atmosphere. From above [ http://leonid.arc.nasa.gov/leonidnews25.html ], meteors create short bright streaks. Visible [ http://leonid.arc.nasa.gov/MS043doc.pdf ] beneath the meteors are clouds lit by reflected moonlight, while visible above is the constellation of Aries [ http://www.astronomical.org/constellations/ari.html ]. The directions [ http://antwrp.gsfc.nasa.gov/apod/ap981208.html ] of the meteor streaks are nearly parallel, confirming that the meteors all originate [ http://antwrp.gsfc.nasa.gov/apod/ap980130.html ] from the same meteor stream. Recent analysis of the 2000 Leonids meteor shower [ http://comets.amsmeteors.org/meteors/showers/leonid2000.html ] indicates to many astronomers that the 2001 Leonids [ http://www.arm.ac.uk/leonid/dust2001.html ] may develop [ http://adsabs.harvard.edu/cgi-bin/nph-bib_query?bibcode=1999JIMO...27...85M ] into a real meteor storm [ http://www.science.nasa.gov/newhome/headlines/ast22jun99_2.htm ], with meteor rates [ http://www.atnf.csiro.au/asa_www/info_sheets/leonids.html ] perhaps exceeding one per second visible from parts of Asia. |
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Hypatia of Alexandria
| Title |
Hypatia of Alexandria |
| Explanation |
Sixteen hundred years ago, Hypatia [ http://www.scottlan.edu/lriddle/women/hypatia.htm ] became one of the world's leading scholars in mathematics and astronomy. Hypatia [ http://www.polyamory.org/~howard/Hypatia/primary-sources.html ]'s legendary knowledge, modesty, and public speaking ability flourished during the era of the Great Library of Alexandria [ http://www.perseus.tufts.edu/GreekScience/Students/Ellen/Museum.html ]. Hypatia [ http://www.polyamory.org/~howard/Hypatia/ ] is credited with contributions to geometry and astrometry [ http://aries.usno.navy.mil/ad_home/ad_homepage.html ], and she is thought instrumental in the development of the sky-measuring astrolabe [ http://www.civilization.ca/membrs/treasure/222beng.html ]. "Reserve your right to think, for even to think wrongly is better than not to think at all," Hypatia [ http://www.astr.ua.edu/4000WS/HYPATIA.html ] is credited with saying. "To teach superstitions as truth is a most terrible thing." |
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Moon, Planets, and Rocket Tr
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| Title |
Moon, Planets, and Rocket Trails |
| Explanation |
Are you an early riser [ http://redfrog.norconnect.no/~poems/poems/09560.html ]? Over the last month or so, the bright planets [ http://antwrp.gsfc.nasa.gov/apod/ap990325.html ] Jupiter and Saturn have come to adorn eastern skies before sunrise [ http://redfrog.norconnect.no/~poems/poems/17572.html ]. In fact, astrophotographer Joe Orman [ http://home.cwix.com/~pam.orman@cwix.com/JoeGallery.html ] anticipated that an early bird's reward for looking east on June 10 would be this pleasing arrangement of Jupiter (top right), a crescent Moon, and Saturn (near center), but he was surprised to also find these eerie, iridescent clouds wafting through the pre-dawn sky over suburban Phoenix, Arizona, USA. The clouds turned out to be rocket [ http://www-istp.gsfc.nasa.gov/stargaze/Srockhis.htm ] engine [ http://www.wff.nasa.gov/ ] trails [ ftp://pao.gsfc.nasa.gov/pub/PAO/Releases/1999/W99-013.htm ] from defense missile tests at the range in White Sands [ http://ruidoso.net/chamber/outdoors/whitesan.html ], New Mexico ... about 300 miles away. While the Moon's phase [ http://aa.usno.navy.mil/AA/data/docs/MoonPhase.html#ninetynine ] is just past new moon [ http://lunar.arc.nasa.gov/history/mythologyh.html ], gone now from the pre-dawn horizon, brilliant Jupiter [ http://galileo.ivv.nasa.gov/ ] and Saturn [ http://www.jpl.nasa.gov/cassini/ ] can still be seen high toward the southeast in the constellation [ http://www.astro.wisc.edu/~dolan/constellations/extra/ constellations.html ] Aries. |
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The Incredible Expanding Cat
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| Title |
The Incredible Expanding Cat's Eye |
| Explanation |
Watch closely. As this animation blinks between two Hubble Space Telescope images [ http://aries.usno.navy.mil:80/ad_home/pne/ ] of NGC 6543 - the first from 1994 and the second from 1997 - the intricate filaments of this nebula are seen to shift. The shift is due to the actual expansion of this gaseous shroud shed by a dying star [ http://oposite.stsci.edu/pubinfo/pr/97/38.html ]! NGC 6543 is more popularly [ http://oposite.stsci.edu/pubinfo/pr/95/01.html ] known as the Cat's Eye [ http://antwrp.gsfc.nasa.gov/apod/ap981101.html ] Nebula. Classified as [ http://www.seds.org/billa/twn/types.html ] a "planetary nebula", its complex, interwoven shells of expanding gas [ http://www.astro.washington.edu/balick/WFPC2/ ] have been castoff by the central star as it evolves from a red giant to its final white dwarf phase. The planetary nebula phase of a star's life is known to be relatively brief, lasting 10,000 years or so. In fact, combined with other data [ http://xxx.lanl.gov/abs/astro-ph/9907313 ], this nebula's detectable shift over a three year period allows the expansion age of its bright inner shells to be estimated at only around 1,000 years while its distance can be gauged at about 3,000 light-years. |
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GRB 060218: A Mysterious Tra
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| Title |
GRB 060218: A Mysterious Transient |
| Explanation |
What is it? Something is happening in a small portion of the sky toward the constellation [ http://en.wikipedia.org/wiki/Constellations ] of Aries [ http://en.wikipedia.org/wiki/Aries ]. Telescopes around the globe are tracking an unusual transient there as it changes day by day. No one is sure what it will do next. The entire space mystery began [ http://gcn.gsfc.nasa.gov/gcn3/4775.gcn3 ] on February 18 when the Earth-orbiting robot Swift satellite [ http://www.nasa.gov/mission_pages/swift/spacecraft/index.html ] noticed an unusual transient began to glow dimly in gamma rays [ http://imagers.gsfc.nasa.gov/ems/gamma.html ]. Dubbed GRB 060218, the object is a type of gamma ray burst [ http://antwrp.gsfc.nasa.gov/apod/ap000702.html ] (GRB) but the way its brightness changes is very unusual. Since detection, GRB 060218 [ http://grad40.as.utexas.edu/grblog.php?view=burst&GRB=20060218A ] has been found to emit light across the electromagnetic spectrum [ http://imagine.gsfc.nasa.gov/docs/science/know_l1/emspectrum.html ], including radio waves and visible light. Pictured above [ http://www.nasa.gov/mission_pages/swift/bursts/oddball_burst.html ], the Sloan Digital Sky Survey (SDSS) image [ http://gcn.gsfc.nasa.gov/gcn3/4777.gcn3 ] of the field of GRB 060218 well prior to its Swift trigger is shown on the left, while the same field, taken by the orbiting Swift satellites' ultraviolet telescope after the Swift trigger, is shown on the right. The oddball GRB [ http://gcn.gsfc.nasa.gov/gcn3/4787.gcn3 ] is visible in the center of the right image. Subsequent observations found a redshift [ http://gcn.gsfc.nasa.gov/gcn3/4792.gcn3 ] for the transient of z=0.033, showing it to be only about 440 million light years [ http://chandra.harvard.edu/photo/cosmic_distance.html ] away, relatively nearby compared to typical GRBs. Whether GRB 060218 represents a new type of gamma ray burst [ http://en.wikipedia.org/wiki/Gamma_ray_burst ], a new type of supernova [ http://heasarc.gsfc.nasa.gov/docs/snr.html ], or an unusual link [ http://antwrp.gsfc.nasa.gov/apod/ap020517.html ] between the GRBs and supernovas has become an instant topic of research. |
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