Документ взят из кэша поисковой машины. Адрес оригинального документа : http://www.arcetri.astro.it/~palla/ANDREAIMMAGINI/ISM/NGC7027b.txt Дата изменения: Tue Jan 30 16:44:17 2001 Дата индексирования: Sat Dec 22 08:11:14 2007 Кодировка: Поисковые слова: рер р р р р р р р р р р р р р

EMBARGOED UNTIL: 9:30 a.m. CST January 16, 1996

PHOTO NO.: STScI-PRC96-05


HUBBLE TELESCOPE PHOTO REVEALS STELLAR
DEATH PROCESS

This NASA Hubble Space Telescope image of planetary nebula NGC 7027
shows remarkable new details of the process by which a star like the
Sun dies.

New features include: faint, blue, concentric shells surrounding the
nebula; an extensive network of red dust clouds throughout the bright
inner region; and the hot central white dwarf, visible as a white dot
at the center.

The nebula is a record of the star's final death throes. Initially the
ejection of the star's outer layers, when it was at its red giant stage
of evolution, occurred at a low rate and was spherical. The Hubble
photo reveals that the initial ejections occurred episodically to
produce the concentric shells. This culminated in a vigorous ejection
of all of the remaining outer layers, which produced the bright inner
regions. At this later stage the ejection was non-spherical, and dense
clouds of dust condensed from the ejected material.

The results are being presented by astronomers Howard Bond, Karen
Schaefer, and Laura Fullton of the Space Telescope Science Institute,
and Robin Ciardullo of Pennsylvania State University, at the 187th
meeting of the American Astronomical Society in San Antonio, Texas.
"When we saw the Hubble photograph of the nebula NGC 7027, we were
astounded by the exquisite wealth of detail that nobody had ever seen
before," said Bond.

The photograph was taken as part of a survey of planetary nebulae,
which are clouds of gas and dust ejected from a star with a mass
similar to that of the Sun as it reaches the end of its life. NGC 7027
is located about 3,000 light-years from Earth in the direction of the
summer constellation Cygnus.

When a star like the Sun nears the end of its life, it expands to more
than 50 times its original diameter, becoming a red giant star. Then
its outer layers are ejected into space, exposing the small, extremely
hot core of the star, which cools off to become a white dwarf.
Although stars like the Sun can live for up to 10 billion years before
becoming a red giant and ejecting a nebula, the actual ejection process
takes only a few thousand years.

The NGC 7027 photograph is a composite of two Hubble images, taken in
visible and infrared light, and is shown in "pseudo-color."

Credit: H. Bond (STScI) and NASA


Image files in GIF and JPEG format and captions may be accessed
on Internet via ftp from oposite.stsci.edu in /pubinfo.

GIF JPEG
PRC96-05 NGC 7027 gif/NGC7027.gif jpeg/NGC7027.jpg

Higher resolution digital versions (300 dpi JPEG) of the release
photograph will be available temporarily in /pubinfo/hrtemp:
96-05.jpg.

GIF and JPEG images, captions and press release text are available via
World Wide Web at URL http://www.stsci.edu/pubinfo/PR/96/05.html, or
via links in http://www.stsci.edu/pubinfo/Latest.html and
http://www.stsci.edu/pubinfo/Pictures.html.