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Hubble Discovers Birth of Galaxy
Joerg gave us the link-up to the latest NASA success. The Hubble Space Telescope has begun peering into the formation of a galaxy, with spectecular results. One of the questions they are currently trying to answer is whether the central bulge or stellar disk came first.
I found this on the nasa homepage:
Pr-Photos page
Donald Savage
o tos.html
Headquarters, Washington, DC Oct. 6, 1999
(Phone: 202/358-1547)
Nancy Neal
Goddard Space Flight Center, Greenbelt, MD
(Phone: 301/286-0039)
Ray Villard
Space Telescope Science Institute, Baltimore, MD
(Phone: 410/338-4514)
RELEASE: 99-107
STARRY BULGES YIELD SECRETS TO GALAXY GROWTH
NASA's Hubble Space Telescope is uncovering important new
clues to a galaxy's birth and growth by peering into its heart --
a bulge of millions of stars that resemble a bulbous center yolk
in the middle of a disk of egg white.
Hubble astronomers are trying to solve the mystery of which
came first: the stellar disk or the central bulge?
Two complementary surveys by independent teams of astronomers
using Hubble show that the hubs of some galaxies formed early in
the Universe, while others formed more slowly, across a long
stretch of time.
Hubble confirms that the evolutionary paths of bulges and
disks are connected. The central bulge stabilizes a galaxy's
development and largely controls the ebb and flow of star birth in
the core. The central bulge holds secrets as to how and when a
galaxy formed. Before Hubble, astronomers had detailed
information only about the complex core of our galaxy, which has a
small bulge peppered with massive young star clusters and a
telltale bar structure funneling gas to the center. Hubble allows
astronomers to see bright star clusters, bars and other structures
deep inside the bulges of other galaxies.
A group led by Reynier Peletier from the University of
Nottingham, in the United Kingdom, has confirmed that the central
bulges of more tightly wound spirals were all created at more or
less the same time in the early universe.
A second team, led by C. Marcella Carollo of Columbia
University in New York, surveyed galaxies that have small bulges
and bar-like structures that bisect the nucleus like the slash
across a no-smoking sign. They found that the bulges in these
galaxies grew more recently, through markedly different processes
happening within the galaxy's disk.
Both surveys used Hubble's precise resolution to peer into
bulbous hubs of more than 200 neighboring galaxies, out to a
distance of 100 million light-years. Using Hubble's visible-light
and infrared cameras to penetrate deep into the cores of the
galaxies, astronomers were able to untangle the stars' true colors
-- a measure of age -- from their apparent colors, which are made
redder by interstellar dust.
Peletier's team used Hubble to look into the center of 20
spiral galaxies that have large bulges. The team found that
elliptical bulges of stars formed over a relatively brief period
very early in the young universe. This could have happened
through the collapse of a single cloud of hydrogen or merger of
primeval star clusters.
"Apparently everywhere in the universe these intermediate-
sized galaxies must have started forming early on," reports
Peletier in a paper to be published in the Monthly Notices of the
Royal Astronomical Society. "The bulges of early spiral galaxies
are old, and at least the outer parts of their disks are
considerably younger."
Carollo's team found that in a different class of spiral
galaxy, a small bulge probably formed early on, but was later fed
by gas flowing into the galaxy's core, likely along a bar-like
structure caused by instabilities in the surrounding disk of
stars. The gas fueled the birth of new stars, and the bulge
inflated like a beach ball as brilliant star clusters populated
the center.
Carollo's results, to be published in the Astrophysical
Journal, show young and old stars in the bulge. The researchers
say that these types of bulges can continue to grow in galaxies in
the present universe, but it is unlikely that they will ever
become as big as those giant bulges that formed when the universe
was young.
The Space Telescope Science Institute is operated by the
Association of Universities for Research in Astronomy, Inc. for
NASA, under contract with NASA's Goddard Space Flight Center,
Greenbelt, MD. The Hubble Space Telescope is a project of
international cooperation between NASA and the European Space
Agency.
- end -
NOTE TO EDITORS: Image files are available on the Internet at:
http://oposite.stsci.edu/pubinfo/latest.html and
http://oposite.stsci.edu/pubinfo/pr/1999/34/pr-ph
The surprise isn't how often we make bad choices; the surprise is how seldom they defeat us.