The deepest views of the cosmos from NASA's Hubble Space Telescope are yielding clues that the very first stars may have burst into the universe as brilliantly and spectacularly as a fireworks finale - except, in this case, the finale came first - long before Earth, our Sun and the Milky Way Galaxy formed.
If this interpretation is correct, it offers a tantalizing possibility that astronomers may behold this stellar blaze of glory when they use NASA's Next Generation Space Telescope and other future space telescopes to probe even farther into the very early universe.
Studies of Hubble's deepest views of the heavens by Kenneth M. Lanzetta of the State University of New York (SUNY) at Stony Brook, and colleagues, lead to the preliminary conclusion that the universe made a significant portion of its stars in a torrential firestorm of star birth which abruptly lit up the pitch-dark heavens just a few hundred million years after the big bang. Though stars continue to be born today in galaxies, the star birth rate could be a trickle compared to the predicted gusher of stars in those opulent early years.
This new idea of a continually escalating rate of star birth the farther Hubble looks back in time offers a dramatic revision of previous Hubble Deep Field studies that proposed that the star birth rate in the early universe ramped up to a "baby boom" about halfway back to the beginning of the universe.
Lanzetta bases his conclusion on a new analysis of galaxies in the Hubble deep fields taken near the north and south celestial poles (in 1995 and 1998 respectively). He reports in an upcoming issue of the Astrophysical Journal that the farthest objects in the deep fields are only the "tip of the iceberg" of an effervescent period of star birth that is unlike anything the universe will ever see again. Lanzetta concludes that 90 percent of the light from the early universe is missing in the Hubble deep fields. "The previous census of the deep fields missed most of the ultraviolet light in the universe; most of it is invisible," he says.
Based on an analysis of galaxy colors, Lanzetta concludes that the farthest objects in the deep fields must be extremely intense, unexpectedly bright knots of blue-white, hot newborn stars embedded in primordial galaxies that are too faint to be seen even by Hubble's far vision. It's like seeing only the lights on a distant Christmas tree and inferring the presence of the whole tree.
The missing light is deduced much as one might deduce the attendance at a neighbor's party by peering over a tall fence. If all one could see were people over six feet tall, one would conclude that there were many more people at the party that couldn't be seen. This conclusion would be based on an assumption about the average heights of people.
Likewise, Lanzetta's analysis is based on carefully extrapolating back into time from the conditions in the present universe. Because such far extrapolations are built on certain assumptions, this conclusion will require further analysis and observation.
Lanzetta next plans to use Hubble's Advanced Camera for Surveys (to be installed in early 2002) to look even deeper into the universe to try to directly verify some portion of the missing light. He will also look for very distant supernovae as an alternate measure of star formation. "Because they are point sources of light, supernovae are not subject to the same cosmological brightness dimming effects like galaxies (which are extended sources of light)," says Lanzetta.
The universe could go on making stars for trillions of years to come, before all the hydrogen is used up, or is too diffuse to coalesce. But the universe will never again resemble the star-studded tapestry that brought light back to the darkness.
NASA Headquarters, Washington, DC
(Phone: 202-358-1547; E-mail: firstname.lastname@example.org)
Goddard Space Flight Center, Greenbelt, MD
(Phone: 301-286-0039; E-mail: email@example.com)
Space Telescope Science Institute, Baltimore, MD
(Phone: 410-338-4514; E-mail: firstname.lastname@example.org)