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Hubble Witnesses the Final Blaze of Glory of Sun-like Stars

Donald Savage
Headquarters, Washington, DC                  December 17, 1997
(Phone:  202/358-1547)

Tammy Jones
Goddard Space Flight Center, Greenbelt, MD
(Phone:  301/286-5566)

Ray Villard
Space Telescope Science Institute, Baltimore, MD
(Phone:  410/338-4514)

RELEASE:  97-287

HUBBLE WITNESSES THE FINAL BLAZE OF GLORY OF SUN-LIKE STARS

       The end of a sun-like star's life was once thought to be 
simple:  the star gracefully casting off a shell of glowing gas 
and then settling into a long retirement as a burned-out white dwarf.

       Now, a dazzling collection of detailed views released today 
by several teams of astronomers using NASA's Hubble Space 
Telescope reveals surprisingly intricate glowing patterns spun 
into space by aging stars:  pinwheels, lawn sprinkler style jets, 
elegant goblet shapes, and even some that look like a rocket 
engine's exhaust.  

     "These eerie fireworks offer a preview of the final stage of 
our own Sun's life," says Bruce Balick of the University of 
Washington, Seattle.  More than simply a stellar "light-show," 
these outbursts provide a way for heavier elements -
-predominantly carbon -- cooked in the star's core, to be ejected 
into interstellar space as raw material for successive generations 
of stars, planets and, potentially, life.

       The astronomers say the incandescent sculptures are forcing 
a re-thinking of stellar evolution.  In particular, the patterns 
may be woven by an aging star's interaction with unseen 
companions:  planets, brown dwarfs, or smaller stars.

       "The first time we looked at the Hubble's breathtaking 
pictures, we knew that our older and simpler ideas of how these 
objects are formed had to be overhauled," said Howard Bond 
of the Space Telescope Science Institute (STScI), Baltimore MD.  
"The basic question is:  How do these nebulae shape themselves?"

       "Hubble's colorful views are a feast for the eyes," said 
Mario Livio, also of the STScI.  "Their beauty is matched only by 
the mystery."

       Surprising new details revealed by the Hubble pictures include:

          *  Unexplained disks and "donuts" of dust girdling a 
star, which pinch outflowing gas.  These may be linked to the 
presence of invisible companions.

          *  Remarkably sharp, inner bubbles of glowing gas -- 
like a balloon inside a balloon -- blown out by the violently 
outflowing gases called a "fast wind" (1000 miles/sec) 
ejected during the final stages of a star's death.

          *  Strange, glowing "red blobs" placed along the edge of 
some nebulae may be chunks of older gas caught in the stellar gale 
of hot flowing material from the dying star.

          *  Jets of high-speed particles that shoot out in 
opposite directions from a star, and plow through surrounding gas, 
like a garden hose stream hitting a sand pile.

          *  Pinwheel patterns formed by symmetrical ejection of 
material so that intricate structures are mirrored on the opposite  
side of a star.

       "We're still reveling in the quality of the data and the 
wealth of new details.  In the longer term, we're going to have to 
confront these strikingly symmetric structures with some 
fundamentally revised ideas about the final stages of a star's 
life," said Balick.  "The lovely patterns of gas argue that some 
highly ordered and powerful process orchestrates the ways stars 
lose their mass, completely unlike an explosion."

       A long-standing puzzle is how these nebulae acquire their 
complex shapes and symmetries.  The red giant stars that preceded 
their formation should have ejected simple, spherical shells of 
gas.  "Hubble's ability to see very fine structural details -- 
usually blurred beyond recognition in ground-based images -- 
enables us to look for clues to this puzzle," said Balick.

       Several teams of astronomers will be observing planetary 
nebulae using new infrared instruments installed on the Hubble 
Telescope last February.  This way, astronomers can glimpse the 
ejection of material at a very early stage long before the 
expelled nebula starts to become visible optically.  Given 
Hubble's high resolution, astronomers also hope to revisit the 
same nebula in a few years to actually see how the shell has 
further expanded into space.  Their observations will be compared 
to predictions and either refine or dismiss current ideas on the 
mass ejection mechanisms of dying stars.

       "These nebulae observed by Hubble give us a preview of our 
own Sun's fate.  Some five billion years from now, after the Sun 
has become a red giant and burned the Earth to a cinder, it will 
eject its own beautiful nebula and then fade away as a white dwarf 
star," warned Bond.

       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-

EDITOR'S NOTE:  Photos and captions are available to news media by 
calling the Headquarters Broadcast and Imaging Branch at 202/358-
1900. 

Color:               B&W:
97-HC-802          97-H-802
97-HC-803          97-H-803

Images also are available at:

http://oposite.stsci.edu/pubinfo/PR/97/38.html and via links in
http://oposite.stsci.edu/pubinfo/Latest.html or
http://oposite.stsci.edu/pubinfo/Pictures.html.