[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

Fw: Astronomers Track Down Asteroids in Hubble Archive

Asteroid hunt is heating up ......

----------
> From: NASANews@hq.nasa.gov
> To: undisclosed-recipients:;
> Subject: Astronomers Track Down Asteroids in Hubble Archive
> Date: Monday, March 09, 1998 4:02 PM
> 
> Don Savage
> Headquarters, Washington, DC                   March 9, 1998
> (Phone:  202/358-1547)
> 
> Diane Ainsworth
> Jet Propulsion Laboratory, Pasadena, CA
> (Phone:  818/354-5011)
> 
> Donna Weaver
> Space Telescope Science Institute, Baltimore, MD
> (Phone:  410/338-4493)
> 
> RELEASE.:  98-39
> 
> ASTRONOMERS TRACK DOWN ASTEROIDS IN HUBBLE ARCHIVE
> 
>        Astronomers have stumbled on an unusual asteroid hunting 
> ground:  the thousands of images stored in the Hubble Space 
> Telescope archive.
> 
>        The hunt, by Robin Evans and Karl Stapelfeldt of NASA's 
> Jet Propulsion Laboratory, Pasadena, CA, has yielded a sizable 
> catch of small asteroids -- about 100.  Their preliminary 
> analysis suggests that a total population of 300,000 small 
> asteroids -- essentially rocks just over half a mile to two 
> miles wide (1-3 kilometers) -- are orbiting between Mars and 
> Jupiter in a band of space debris known as the main belt.  
> Currently, there are 8,319 confirmed main-belt asteroids whose 
> orbits have been measured, and about the same number have been 
> sighted but not confirmed.
> 
>         Most astronomers stalk the Hubble archive for bigger 
> game, such as quasars, distant galaxies, and supernovae, but 
> Evans and Stapelfeldt have discovered that the pursuit of 
> smaller prey such as asteroids can be equally successful. 
> 
>         Over a three-year period, the two astronomers and their 
> collaborators have searched through more than 28,000 Wide Field 
> and Planetary Camera 2 (WFPC2) images, looking for wide, 
> looping streaks of light, the telescope's tell-tale signatures 
> of asteroids.  Most of the ones they found are too faint to be 
> observed by current ground-based search programs.  Hubble 
> captures their images purely by accident:  Nearby asteroids 
> inevitably wander across the telescope's field of view while 
> other, higher priority targets are being observed.
> 
>        "The archive images are distributed fairly evenly across 
> the sky, so we find asteroids according to both their position 
> in the sky and their number," Evans said.  "As expected, we see 
> the asteroids concentrated towards the ecliptic plane and we 
> see small asteroids because they are the most numerous.  Small 
> main-belt asteroids such as these are the ones most likely to 
> evolve into Earth-crossing asteroids due to encounters with 
> their larger neighbors.  Some of the asteroids in our survey 
> could eventually migrate toward Earth."  
> 
> 	The Hubble archives represent a newly tapped information 
> resource which could help scientists more precisely estimate 
> the risks the asteroids pose to Earth.
> 
>         According to Evans and Stapelfeldt, the Hubble archival 
> data also strongly limit the number of small comets that could 
> be passing very near Earth.  Last year, Dr. Louis A. Frank of 
> the University of Iowa in Iowa City, using data from NASA's 
> Polar spacecraft, reported he found evidence that about a dozen 
> small comets strike Earth's upper atmosphere each minute.  
> Evans and Stapelfeldt estimate the such small comets should be 
> bright enough to produce thousands of detectable trails in the 
> Hubble archival images, but these were not seen. 
> 
>        The Hubble images capture an asteroid as a long trail 
> produced by its motion across the camera's field of view.  The 
> trails appear like the streaks of light found on photos taken 
> at night of speeding cars with their headlights on.
> 
>        Finding asteroids isn't what the two astronomers 
> originally had in mind.  As members of the WFPC2 science team, 
> Evans and Stapelfeldt were examining test images of distant 
> stars and galaxies to ensure that the new camera was 
> functioning properly.  These were among the first images taken 
> with WFPC2, which had restored sharp focus to Hubble's images 
> when it was installed in late 1993. Stapelfeldt's wife, Deborah 
> Padgett (also an astronomer), pinpointed the first asteroid in 
> 1994 while looking at images on the couple's home computer.  
> Intrigued, Evans and Stapelfeldt began combing through more 
> than 1,600 of the science team's survey photos, finding 12 more 
> asteroids.  This discovery prompted their large-scale search, 
> by eye, of two years worth of Hubble archival images.
> 
>        Evans' and Stapelfeldt's initial results are reported in 
> the February 1998 issue of the research journal Icarus.
> 
>        The Space Telescope Science Institute is operated by the 
> Association of Universities for Research in Astronomy, Inc. 
> (AURA) for NASA, under contract with the Goddard Space Flight 
> Center, Greenbelt, MD.  The Hubble Space Telescope is a project 
> of international cooperation between NASA and the European 
> Space Agency (ESA).
> 
>                              - end -
> 
> NOTE TO EDITORS:  A photo and caption are available via the 
> World-Wide Web at:
> 
> http://oposite.stsci.edu/pubinfo/latest.html       or
> http://oposite.stsci.edu/pubinfo/pictures.html
> 
>        GIF and JPEG images are available via anonymous ftp to 
> oposite.stsci.edu in: 
>  
> /pubinfo/gif/9810.gif and /pubinfo/jpeg/9810.jpg.
>