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Case, WIYN astronomers discover new galaxy orbiting Andromeda (Forwarded)

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Old November 7th 03, 04:27 PM
Andrew Yee
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Default Case, WIYN astronomers discover new galaxy orbiting Andromeda (Forwarded)

Office of University Communication
Case Western Reserve University

For more information, contact:

Dr Heather Morrison, CWRU
216-368 6698,

Paul Harding, 216-368 6696,

Susan Griffith, 216-368-1004,

For immediate release: September 19, 2003

Case, WIYN astronomers discover new galaxy orbiting Andromeda

CLEVELAND -- Case Western Reserve University astronomers have announced the
discovery of a new galaxy, termed Andromeda VIII. The new galaxy is so
widespread and transparent that astronomers did not suspect its existence until
they mapped the velocity of stars thought to belong to the well-known and nearby
large Andromeda spiral galaxy and found them to move independently of Andromeda.

Heather Morrison, Paul Harding and Denise Hurley-Keller of Case's department of
astronomy and George Jacoby of the WIYN Observatory in Tucson, Ariz., will
report their discovery in an upcoming article, accepted for publication in
Astrophysical Journal Letters.

"This is particularly exciting because it allows us to watch the ongoing growth
of the nearby Andromeda galaxy from smaller galaxies," says Morrison.

The astronomers used Case's Burrell Schmidt telescope and the 3.5m WIYN
telescope to identify the galaxy. Both telescopes are located at Kitt Peak
National Observatory near Tucson, AZ. NOAO is operated by the Association of
Universities for Research in Astronomy (AURA) Inc., under a cooperative
agreement with the National Science Foundation

The newly found galaxy is being torn apart into star streams which trace its
orbit around the Andromeda galaxy in the way a jet's contrail shows its route.
Andromeda is the nearest large spiral galaxy to our own Milky Way galaxy -- a
"mere" two million light years away. It is visible as a hazy glowing object to
the naked eye in a dark sky in the northern hemisphere and is found in the
constellation of Andromeda.

Discovered over 1,000 years ago by the Persian astronomer Azophi Al-Sufi,
Andromeda is a member of the Local Group of approximately 30 galaxies in the
Milky Way's celestial backyard.

In early August, as Morrison finished analyzing the data of these stars from the
Andromeda celestial neighborhood, she was amazed to find a new dwarf galaxy
orbiting Andromeda. It is a "see-thru" galaxy, which was only discovered once
the astronomers obtained velocity measurements for some of its stars, said Morrison.

She adds that the reason Andromeda VIII escaped detection was the fact that it
is located in front of the bright regions of Andromeda's galaxy disk.

Andromeda VIII's total brightness is comparable to that of Andromeda's
well-known companion M32, a small nearby galaxy, but Andromeda VIII is spread
over an area of the sky as much as ten times or more larger than M32. Its
elongated shape is caused by Andromeda's gravitational pull, which has stretched
it out due to the stronger gravity on the side nearest Andromeda.

Morrison and her collaborators also suggested that a very faint stream of stars,
detected near the large Andromeda galaxy in 2001 by the Italian Astronmer R. A.
Ibata and colleagues, was pulled off Andromeda VIII in an earlier passage around
the parent galaxy. "Future research in this area should provide rich and
fruitful results," stated Morrison.

Theory has predicted for decades that galaxies are assembled in a "bottom-up"
process, forming first as small galaxies that later merge to form large ones.

"Since 1994, when Ibata and colleagues announced the discovery of a new
satellite in the process of being swallowed by the Milky Way, we have been able
to actually see the process taking part in our own galaxy," stated Morrison.
"Now we find the same process in our nearest large neighbor."

She adds that now it looks like Andromeda is even more inundated by small
galaxies than the Milky Way. Ibata and colleagues have taken deep images of
Andromeda which show a rich collection of star streams wreathed about the
galaxy. Morrison and her colleagues have now identified the source of one of
these star streams. They plan future observations to connect the different star
streams with their progenitors, and thus learn more about the properties of the
companion galaxy, the Andromeda galaxy and its elusive dark matter halo.

The galaxy research was supported by a five-year National Science Foundation
Early Career Development Award.

An image of Andromeda with the position of Andromeda VIII marked in graphics by
Case student Nancy Lin over a photo by Robert Gendler is available at
A movie which shows a large galaxy tearing apart a smaller one in the way that
the Andromeda spiral is tearing apart Andromeda VIII is available at
http://www.astro.wesleyan.edu/~kvj/mw.html (Movie credit: Kathryn Johnson)

The Burrell Schmidt telescope is part of Case's Warner and Swasey Observatory.
The WIYN 3.5-meter telescope is a partnership of the University of Wisconsin,
Indiana University, Yale University and the National Optical Astronomy
Observatory (NOAO). NOAO is operated by the Association of Universities for
Research in Astronomy (AURA) Inc., under a cooperative agreement with the
National Science Foundation.


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