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UIS faculty member is lead author of article suggesting change in massive star

November 13, 2006

Team gathered data using Hubble Space Telescope

John Martin

SPRINGFIELD – John Martin, assistant professor of Astronomy/Physics at the University of Illinois at Springfield, is the lead author of a paper to be published in the December issue of Astronomical Journal suggesting that the most massive star in our galaxy is about to undergo dramatic change.

Martin, who came to UIS from the University of Minnesota, is part of a team that spent the past eight years monitoring the star Eta Carinae (pronounced "ate-ahh car-eee-nahh") using the Hubble Space Telescope.

He explained, "The superior resolution of the Hubble Space Telescope has given us a huge advantage over ground-based observers, who are unable to resolve the star from its cocoon-like nebula. We discovered a significant increase in the star's brightness and believe that within the next few decades it should break out of the shell of material enshrouding it."

Eta Carinae is located in the southern constellation Carinae.

Eta Carinae is in the southern constellation Carinae and is not visible to observers in the northern hemisphere.

In the 1850s Eta Carinae underwent a massive eruption and briefly became the brightest star in the night sky. Martin explained that during that eruption the star shed the equivalent of 20 times the mass of our own Sun, which formed a cocoon-like reflection nebula that has masked the star from direct view ever since.

Martin and company believe that the star's accelerating brightness heralds an impending change of great significance. "To this point," he said, "the cocoon has probably been maintained by a dense flow of material off the star's surface. However, our data suggests that the star's atmosphere is changing in a way that will cause the cocoon to dissipate and allow us the first clear view in over 150 years." They also predict that over the coming decades the surrounding nebula will ionize and once again make Eta Carinae a very bright object, visible to the naked eye in the southern hemisphere.

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Astronomy/Physics at UIS

Martin said that Eta Carinae has a mass about 120 times that of the Sun, making it one of the most massive stars in our galaxy. Astronomers think that the first stars, which lived and died before our own Sun, were very massive like Eta Carinae and manufactured all the atoms heavier than helium in our bodies. "By studying Eta Carinae, astronomers learn a lot about our own origins and how atoms manufactured by the first generation of stars found their way into the cloud of gas that surrounded our still-forming Sun," he said. "One day Eta Carinae will almost certainly go supernova, and astronomers have never had a better opportunity to closely study a star before such a cosmic explosion."

Martin spent three years as a postdoctoral research associate at the University of Minnesota studying data from the Hubble Space Telescope. He holds the Ph.D. in astrophysics from Case Western Reserve University and an undergraduate degree in the same subject from the University of Virginia.

The upcoming article is titled "The Chrysalis Opens: Photometry from the Eta Carinae Hubble Space Telescope Treasury Project, 2002-2006." Co-authors with Martin are Kris Davidson and M.D. Koppelman, both of the University of Minnesota. Martin will also present a poster session summarizing the article at the American Astronomical Society meeting to be held in Seattle in January.

To see pictures of Eta Carinae, go to http://etacar.umn.edu/etainfo/images/; for general information on the star, go to http://etacar.umn.edu/etainfo/. More information about the Hubble Space Telescope is available at http://hubblesite.org/.

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