Don Savage
Headquarters, Washington, DC              June 6, 1995
(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:  95-129 

HUBBLE OBSERVES THE FIRE AND FURY OF A STELLAR BIRTH

     NASA's Hubble Space Telescope has provided a detailed 
look at the fitful, eruptive, and dynamic processes 
accompanying the final stages of a star's "construction." 

     Images from the orbiting observatory reveal new 
details that will require further refinement of star 
formation theories, according to several independent teams 
of astronomers who have used Hubble to observe different 
embryonic stars.  The Hubble observations shed new light on 
one of modern astronomy's central questions: how do tenuous 
clouds of interstellar gas and dust make stars like our Sun?

     "For the first time we are seeing a newborn star close 
up -- at the scale of  our solar system -- and probing the 
inner workings," said Chris Burrows of the Space Telescope 
Science Institute, Baltimore, MD, and the European Space 
Agency.  "In doing so we will be able to create detailed 
models of star birth and gain a much better understanding 
of the formation of our Sun and planets." 

     The Hubble images provide a dramatically clear look at 
a collapsing circumstellar disk of dust and gas that builds 
the star and provides the ingredients for a planetary 
system, blowtorch-like jets of hot gas funneled from deep 
within several embryonic systems, and machine-gun like 
bursts of material fired from the stars at speeds of a 
half-million miles per hour.

     The images offer clues to events that occurred in our 
solar system when the Sun was born 4.5 billion years ago.  
Astronomers commonly believe that Earth and the other eight 
planets condensed out of a circumstellar disk because they 
lie in the same plane and orbit the Sun in the same 
direction.  According to this theory, when the Sun ignited 
it blew away the remaining disk, but not before the planets 
had formed.

      "The Hubble images are opening up a whole new field of 
stellar research for astronomers and clearing up a decade's 
worth of uncertainty," added Jeff Hester of Arizona State 
University, Tempe, AZ.  "Now we can look so close to a star 
that many details of star birth become clear immediately."

     The key new details revealed by the Hubble pictures:

     *    Jets originate from the star and the inner parts 
of the disk and become confined to a narrow beam within a 
few billion miles of their source.  It's not known how the 
jets are focused, or collimated.  One theory is that 
magnetic fields, generated by the star or disk, might 
constrain the jets.

     *    Stars shoot out clumps of gas that might provide 
insights into the nature of the disk collapsing onto the 
star.  The beaded jet structure is a "ticker tape" 
recording of how clumps of material have, episodically, 
fallen onto the star.  In one case, Hubbleallowed 
astronomers to follow the motion of the blobs and measure 
their velocity.

     *    Jets "wiggle" along their multi-trillion-mile 
long paths, suggesting the gaseous fountains change their 
position and direction.  The wiggles may result from the 
gravitational influence of one or more unseen protostellar 
companions.

     More generally, Hester emphasizes:  "Disks and jets 
are ubiquitous in the universe.  They occur over a vast 
range of energies and physical scales, in a variety of 
phenomena."  Gaining an understanding of these young 
circumstellar structures might shed light on similar 
activity in a wide array of astronomical phenomena:  novae, 
black holes, radio galaxies and quasars.

     "The Hubble pictures appear to exclude whole classes 
of models regarding jet formation and evolution," said Jon 
Morse of the Space Telescope Science Institute.

     A disk appears to be a natural outcome when a slowly 
rotating cloud of gas collapses under the force of gravity 
-- whether the gas is collapsing to form a star, or is 
falling onto a massive black hole.

     Material falling onto the star creates a jet when some 
of it is heated and blasted along a path that follows the 
star's rotation axis, like an axle through a wheel. 

     Jets may assist star formation by carrying away excess 
angular momentum that otherwise would prevent material from 
reaching the star.  Jets also provide astronomers with a 
unique glimpse of the inner workings of the star and disk.  
"Not even the Hubble Telescope can watch as material makes 
its final plunge onto the surface of the forming star, but 
the new observations are still telling us much about that 
process," said Hester.

     Burrows, Hester, Morse and their co-investigators 
independently observed several star birth sites in our 
galactic neighborhood.  "All of these objects tell much the 
same story," Hester emphasized.  "We are clearly seeing a 
process that is a crucial part of star formation, and not 
just the peculiarities of a few oddball objects."

     The researchers all agree that the Hubble pictures 
generally confirm models of star formation but will send 
theorists back to the drawing board to explain the details.  
The researchers emphasize that future models of star 
formation will have to take into account why jets are 
ejected from such a well-defined region in the disk, why 
jets are collimated a few billion miles out from the star, 
and why gas in the jets is ejected quasi-periodically.

			- end -

EDITOR'S NOTE:  Images to illustrate this release are 
available for news media representatives by calling the 
Headquarters Broadcast and Imaging Branch on 202/358-1900.  
Photo numbers are:

Caption description                      Color           B&W
Hubble Views of Three Stellar Jets     95-HC-292       95-H-297
Motion Of Jets From An Embryonic Star                  95-H-298
Pair of Jets from a Young Star         95-HC-293       95-H-299
Wiggling Jet from a Wobbling Star                      95-H-300

Image files in GIF and JPEG format may be accessed on 
Internet via anonymous ftp from ftp.stsci.edu in the 
/pubinfo directory:

                                    GIF          JPEG

PRC95-24a      HH30/HH34/HH47   gif/JetDisk3 jpeg/JetDisk3
PRC95-24b      HH30 Jet Motion  gif/HH30     jpeg/HH30
PRC95-24c      HH1/HH2 Details  gif/HH1-2    jpeg/HH1-2
PRC95-24d      HH47 Jet Detail  gif/HH47     jpeg/HH47

The same images are available via World Wide Web from these 
URL locations: http://www.stsci.edu/pubinfo/PR/95/24.html, 
or via links in http://www.stsci.edu/public.html.