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Studying Massive Supernovas at AMNH

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Curator Michael Shara seeks Wolf-Rayet Stars in the spiral galaxy Messier 101, pictured here in high-definition by the Hubble Space Telescope. 
© NASA/ESA/K.D. Kuntz/F. Bresolin/J. Trauger/J. Mould/Y.-H. Chu

The fifth floor of the Rose Center for Earth and Space is home to the Museum’s Department of Astrophysics, which includes a research group of two dozen graduate students, research scientists, and postdocs. Michael Shara, curator of the new exhibition Beyond Planet Earth: The Future of Space Exploration, is one of three curators in the department. Below is the first in a series of features on the curators’ areas of research.

Curator Michael Shara studies stellar populations in the Milky Way and nearby galaxies. Over the last decade, he has focused on stars known as Wolf-Rayets—hot, ephemeral bodies that start their lives 20 to 80 times more massive than the Sun and then shed much of that mass over a lifespan of a few hundred thousand years until they explode as Type 1b or 1c supernovae, which occur when a massive star’s core collapses. There are now 600 Wolf-Rayet stars known in the Milky Way, an 80 percent increase since 2006. Shara’s team has found and characterized the majority of them. His “best” and rarest specimens are from the far side of the Milky Way, which is still terra incognita to astronomers.

“We think that supernovae occur on average every 50 to 100 years in the Milky Way,” says Shara. “Astronomers detected two dozen neutrinos from a supernova in the Large Magellanic Cloud in 1987, but a supernova in our galaxy would be invaluable because it would be only about 10,000 light years away and hundreds of times brighter. In addition, we can now measure gravity waves—the rattling of space time—as well as neutrinos, and that would help us understand the collapse of a star’s core into a black hole as it becomes a supernova.”

Shara is increasing his odds of finding massive supernovae by also looking for Wolf-Rayet stars in Messier 101, a spiral galaxy 100 times farther away, or 10 million light years from Earth. Using the Hubble Space Telescope, Shara has gathered a list of candidates by imaging the galaxy through an optical filter that transmits only the light of ionized helium—where Wolf-Rayet stars shine brightest. These candidates will be investigated further by colleagues working on the massive 8-meter Gemini telescope in Hawaii. So far, Messier 101 seems to be four to five times more supernova-rich than the Milky Way. Shara just might get his wish of “seeing” a massive supernova erupt in his lifetime.

Beyond Planet Earth: The Future of Space Exploration is now on view at the Museum. Click here to buy tickets, and click here to download the Beyond Planet Earth Augmented Reality App before your visit.

This story originally appeared in the Fall issue of Rotunda, the Member magazine.