Astronomers
are watching a galaxy rip to shreds,
a finding that could help reveal how galaxies go from stellar riches to rags.
While
looking at the galaxy cluster Abell 2667 with the Hubble Space Telescope,
scientists found a spiral
galaxy which they nicknamed the "Comet Galaxy."
The gas and
stars of the Comet Galaxy--moving
through the cluster at speeds of more than 2 million mph--are being stripped
away by the tidal forces of the cluster. Also, the pressure of the
cluster's scorching gas plasma--known as ram pressure stripping--is adding to the
damage.
"This
unique galaxy, situated 3.2 billion light-years from Earth, has an extended stream of bright
blue knots and diffuse wisps of young stars driven away by the tidal forces and
the ram pressure stripping of the hot dense gas," said Jean-Paul Kneib, a study
collaborator from the Laboratoire d'Astrophysique de Marseille.
Galaxy
metamorphosis
Galaxies
come in many shapes and sizes. Elliptical galaxies generally have little gas
and dust and mainly consist of old stars. Unlike spiral galaxies, which are
generally found in isolation, elliptical galaxies are spotted in the center of
crowded galaxy clusters.
Up until
now, it's been a mystery as to how a gas-rich spiral galaxy evolves into a gas-
poor irregular galaxy or a gas-poor elliptical galaxy. Also, when the Universe was half its present age,
only one in five galaxies was a gas-poor elliptical galaxy. This has left
astronomers wondering where all of the present day elliptical galaxies came
from.
Elliptical
galaxies, scientists suspect, are transformation products of other types of
galaxies, something no one has seen because the process takes billions of
years. What they are observing now is some 200 million years into such a
process.
"By
combining Hubble observations with various ground- and space-based telescopes, we have been able to
shed some light on the evolutionary history of galaxies", said study team
leader Luca Cortese of Cardiff University, UK.
A losing
battle
The Comet
Galaxy--with a little more mass than the Milky
Way--will eventually lose its battle against the tidal forces and pressures
of the hot plasma acting on it and end up a gas-poor galaxy with a collection
of old stars.
"Millions
of now homeless stars have been snatched away from their mother galaxy, which
will lead the galaxy to age prematurely," said study co-investigator Giovanni
Covone of Osservatorio Astronomico di Capodimonte.
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