Case Western Reserve University astronomers have discovered a new galaxy, termed Andromeda VIII.

The new galaxy is so widespread and transparent that astronomers did not even suspect its existence until they mapped the velocity of stars thought to belong to the nearby, well-known Andromeda spiral galaxy and found them to move independently.

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.

In early August, as Morrison finished analyzing the data of stars from the Andromeda celestial neighborhood, she said she was amazed to find a new dwarf galaxy orbiting Andromeda. She said the "see-thru" galaxy Andromeda VIII has escaped detection because it is located in front of the bright regions of Andromeda's larger galaxy disk.

Andromeda VIII's total brightness is comparable to that of Andromeda's well-known companion M32, a small nearby galaxy. But the newly discovered galaxy is spread over an area of the sky as much as 10 or more times the size of M32. The researchers said Andromeda VIII's elongated shape is likely the result of the larger galaxy's gravitational pull on one side of the new galaxy.

Morrison and her collaborators also suggest that a very faint stream of stars, detected near the large Andromeda galaxy in 2001 by the Italian Astronomer 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," Morrison said.

The astronomers used Case's Burrell Schmidt telescope and the 3.5m WIYN telescope to identify the new galaxy. Both telescopes are located at Kitt Peak National Observatory near Tucson, Ariz.

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 Inc., under a cooperative agreement with the National Science Foundation (NSF).

The galaxy research has been supported by a five-year NSF Early Career Development Award.

Return to the online edition of the 9-25-03 Campus News.