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.