Milky Way could hold remnants of last galactic 'meal'
A hypothetical composite image of what a collision between the Milky Way and the M31 (or Andromeda) galaxy might look like
(CNN) -- Some celestial detective work strongly suggests that the
Milky Way consumed a smaller galaxy billions of years ago. And
relics of the massive meal could still exist in our galaxy,
astronomers said Monday.
After observing 1,500 sun-like stars, an international team of
scientists determined that the unusual movement and composition
of certain stars could reveal the presence of the galaxy's last
The researchers, hoping to expand the search to 10,000 stars,
think that their galactic survey could shed light on the origins
of the galaxy.
"The Milky Way is a fairly large galaxy and we believe it was
formed by the merging of a number of smaller galaxies," said
Johns Hopkins University physicist Rosemary Wyse in a statement.
Wyse and fellow investigators in England and Australia are
attempting to map the far reaches of the Milky Way. They are
focusing their search on stars away from the thin central disk
that dominates the galaxy.
A spiral galaxy with a thin disk of gas and stars, the Milky Way
also has "a thick disk … puffed up to a higher scale height than
the rest of the disk," Wyse said.
The extent of the "puffing up" suggests that the Milky Way last
consumed a satellite galaxy when it was extremely young, around
10 billion years ago, according to the astronomical team.
Preliminary observations offer tantalizing hints that remnants of
the galactic merger exist, the researchers said. They hope their
expanded search will confirm the existence of the galactic
"Just as the tidal interactions between the moon and the Earth
cause distortions, there's going to be tidal interactions as a
satellite galaxy comes into the Milky Way, and those can be
severe enough to actually tear mass off the outer parts of the
satellite galaxy," Wyse said.
"Those stars should be left behind on an orbit that is similar to
the orbit of the satellite galaxy at that time."
Such cosmic collisions could take place again in the future. Astronomers predict the Milky Way and Andromeda, the nearest galaxy, will crash into one another billions of years from now.
NASA image reveals a battle of galactic forces
November 14, 2000
Hubble records fireworks when galaxies collide
November 2, 2000
Chandra's X-ray vision of universe awes, puzzles
June 8, 2000
The Johns Hopkins University
The Anglo-Australian Observatory
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