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

Mini-Comet Theory Setback?

SKY & TELESCOPE'S NEWS BULLETIN
DECEMBER 5, 1997

MINICOMET THEORY SETBACK?

More than a decade ago Louis A. Frank and John B. Sigwarth (University of 
Iowa) came to the conclusion the Earth is pummeled by house-size comets 
many thousands of times each day. They have fought an uphill battle to 
support it ever since. Last May Frank brought forth new evidence from 
NASA's Polar spacecraft, who's ultraviolet-light images of Earth's 
atmosphere show what Frank purports to be water-induced "holes" from 
minicomet impacts.

Now the minicomet scenario has been hit again. George Parks (University of 
Washington) and his colleagues reexamined the Polar data but did not find 
support for Frank's claims. The researchers note in the December 15th issue 
of Geophysical Research Letters that the spots in Polar's ultraviolet views 
show no clear differences from dark areas seen in preflight calibration 
images. Furthermore, the Polar spacecraft developed an unplanned wobble 
once in orbit. Thus views longer than 6 seconds exhibit a 10-pixel-wide 
smearing. Park and his colleagues assert that no spots conclusively show 
this characteristic either. Finally, the scientists attribute cometlike 
streaks in some images to cosmic-ray particles striking the detector.

Frank counters these criticisms by saying that the new analysis is 
fundamentally flawed. He explains that Parks did not consider the larger 
atmospheric holes seen by Polar and only studied the smaller ones that ARE 
instrumental artifacts. Also, in most cases the holes' would not reveal the 
effects of the spacecraft's wobble, and Frank insists that some images DO 
exhibit it. Stay tuned -- these and other results will be discussed at a 
meeting of the American Geophysical Union on December 9th.


[snip]

CALL FOR COMET HALE-BOPP IMAGES

The Japanese X-ray satellite ASCA will observe Comet Hale-Bopp this week, 
on December 5-6, for a team of Japanese and American astronomers. Because 
the comet is now in the southern sky, it is beyond the reach of ground-
based telescopes in Japan and the United States. So the researchers are 
appealing to amateur and professional astronomers in the Southern 
Hemisphere to record visible-light CCD images of the comet for comparison 
with the ASCA results. ASCA is scheduled to study Comet Hale-Bopp from 
05:45 UT on December 5th through 03:30 UT on December 6th. If you succeed 
in making CCD observations of the comet during this period, please contact 
Jun-ichi Watanabe, National Astronomical Observatory of Japan, Osawa, 
Mitaka, 181 Tokyo, Japan; phone: +81-422-34-3644; fax: +81-422-34-3810; e-
mail: watanabe@pub.mtk.nao.ac.jp. And please tell Dr. Watanabe that you saw 
this alert on the News Bulletin.

[snip]

=========================================================================== 
Copyright 1997 Sky Publishing Corporation.  S&T's Weekly News Bulletin and 
Sky at a Glance stargazing calendar are provided as a service to the 
astronomical community by the editors of SKY & TELESCOPE magazine.  
Widespread electronic distribution is encouraged as long as these paragraphs 
are included.  But the text of the bulletin and calendar may not be 
published in any other form without permission from Sky Publishing (contact 
permissions@skypub.com or phone 617-864-7360).  Illustrated versions, 
including active links to related Internet resources, are available via SKY 
Online on the World Wide Web at http://www.skypub.com/.