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The M 80 Nova Bursters

Dr. Michael M. Shara

Curator and Curator-in-Charge, Department of Astrophysics, Division of Physical Sciences; and curator of Einstein

Dr. Shara and his research group are conducting an exhaustive survey to inventory and "weigh" all 100,000 stars nearest to Earth. More than one billion stars are being examined in the search. The survey has already determined that many low luminosity stars remain undiscovered just a few light years away, and that a significant portion of the local "dark" matter is concentrated in stars 100 to 100,000 times fainter than the Sun.

Dr. Shara uses the Hubble Space Telescope to survey the densest cores of globular clusters to retrieve and characterize the predicted collision products. These include some of the most exotic stars known to astrophysicists: "blue stragglers." By accurately weighing these stars, Shara and his collaborators have demonstrated that many are at least twice as massive as all other stars in a globular cluster. This strongly supports the hitherto theoretical collisional origin for blue stragglers.

Read an interview with Dr. Shara about the Einstein exhibition.

Prior to joining the Museum in 1999, Michael Shara was with the Space Telescope Science Institute at Johns Hopkins for 17 years, where he was responsible for the peer review committees for the Hubble Space Telescope. Dr. Shara received his Ph.D. in 1977 from Tel-Aviv University. He holds a M.Sc. and B.Sc. from the University of Toronto, and studied mathematics at McGill University. He has been both visiting and adjunct professor at Columbia University; associate astronomer and astronomer with tenure at Space Telescope Science Institute; visiting assistant in the Department of Physics at Arizona State University; and National Research Council of Canada Postdoctoral Fellow in the Department of Physics at the University of Montreal. He was a graduate student and research assistant in the Department of Physics and Astronomy at Tel-Aviv University and the Department of Astronomy at the University of Toronto. Dr. Shara's research interests include the structure and evolution of novae and supernovae; collisions between stars and the remnant descendants of those collisions; and the populations of stars inhabiting star clusters and galaxies. He has served on the National Science Foundation Compact Stars Review Panel, Infrared Processing and Analysis Center User's Committee, Cerro Tololo InterAmerican Observatory User's Committee, and NASA/IPAC Extragalactic Database Project Advisory Committee, among others.

Astrophysics at the American Museum of Natural History
The Museum's Department of Astrophysics, created in July 1999 and chaired by Michael Shara, conducts an ambitious research program, provides scientific expertise in supporting the education and outreach activities of the Frederick Phineas & Sandra Priest Rose Center for Earth and Space, and conveys the excitement of modern astronomy to the public.

The department is actively carrying out research in observational, theoretical, and computational astrophysics. Museum scientists are using all the tools available to modern astrophysicists-ground and space-based telescopes, supercomputers, and visualization tools-many of which are located within the facility. Active research collaborations exist between Museum department members and faculty at Princeton University, Columbia University, and other major research universities.

The research specialties of the department members cover a wide range of modern astrophysics, including the evolution of interstellar clouds collapsing to form stars, stellar collisions and their progeny in dense star clusters, the differing populations of stars in our Milky Way galaxy and its neighbors, the fates of planets in star clusters, and the birth and evolution of the first generation of stars. Stellar Collisions, Mergers, and Their Consequences, an international meeting of leading astrophysicists, was held at the Rose Center May 31-June 2, 2000. The event was the first-ever professional or amateur meeting on this topic. The department also hosts regular colloquia for area astrophysicists, including one held December 2001 on the topic of extrasolar planets.

David Zurek

I am a research assistant for Mike Shara at STScI. The specific studies that we are involved with are the structure of nova shells, the discovery of Dwarf novae in globular clusters, and the discovery of novae in other galaxies. (I will explain what a nova and a dwarf nova are shortly.) Projects that I'm involved with other people include the comparison of stellar populations with theory and trying to understand why different globular clusters that appear to be the same age contain differences. (I will explain this shortly as well.)

A nova is a binary which has a white dwarf star and a companion that is dumping material onto it. When enough material is dumped onto the white dwarf the material explodes and gets ejected from the white dwarf. We study this ejected material to try and determine just how much material it takes for this explosion to take place and to determine how the eruption itself effects the structure of the shell. A dwarf nova is similar but instead of the eruption coming from the surface of the white dwarf it occurs in a disk of material that is being created from the material stripped off the companion. We're trying to find these objects in globular clusters, which or clusters of stars that orbit around our galaxy, because there are suppose to be lots of them there but as yet very few have been found. Globular clusters themselves are interesting because they contain so many stars that formed at the same time. This allows us to test theoretical models of how stars evolve. However, globular clusters still have differences that we can not explain and this is one of the areas which I am currently exploring.

What I do is write proposals for telescope time (basically an application form that is judged by other astronomers), observe at the telescope if we are doing ground based observations, process the data, analyze and model the data and finally to help write up our results for publication. This whole process is fun and exciting but by far my favorite parts are observing and the analysis and modeling. To me this is kind a like exploring and I get excited every time I receive time on a telescope and when I receive new data.

I guess I decided that I wanted to be an astronomer when I was about 12 or 13 years old. In grade 6 we did some reports on the solar system and these got me very interested in astronomy. Science always interested me but something about astronomy, I guess because it's such an unknown, just excited me. I grew up in a small town (8000 people) in the mountains of British Columbia, Canada and we didn't have too many things like science centers or stuff like that (the closest big city is Vancouver which is an 8 hour drive away). I did contact a professor at the local college and he was kind a enough to take me and a couple of friends to use some of the telescopes that the college had. One of the things I did do was to write NASA a letter and they sent me catalogs and some information. I also bought books and posters with the money I earned on my parents orchard. I think watching the shows "Cosmos" and then buying the book when a long way in furthering my interests. As I got older I got interested in computers which has helped me greatly in my work.

The best thing about my job is the not knowing what I will find. Exploring new areas of astronomy and trying to understand what we find is very exciting and interesting to me. I guess one of my least favorite parts is in the initial reduction or image processing of the data. It is completely necessary but it is pretty much the same every time and for every new piece of data. I guess it gets a little tedious.

I'm not sure I did anything special to prepare for my career. I read lots of books on astronomy, such as Cosmos by Carl Sagan, and I watched every show on PBS that had something to do with astronomy. I think today things have become more competitive and I would suggest that someone who wants to pursue a career in astronomy should study and math and physics and just importantly should learn as much as they can about computers.

There are two people that had a very large influence on me and my eventual success in this career. The first was a professor at a small college who took me and my friends to the telescopes that the college owned and showed us the planets and other interesting objects in the sky. He gave us books to read and he helped us make a telescope. My friends and I would regularly get together to look at the stars and watch a meteor shower like the Pleiades. Later once I was at University a professor there hired me to assist him. He encouraged my ideas and supported them as well. He then allowed me to apply or telescope time and to conduct research that I was interested in. These two people I owe a lot to and I will always be grateful to them for the support that they have given me.

Personal Info: I am unmarried and have no children. I will probably be getting a dog this year sometime. I played rugby for the University of Victoria. I guess because I grew up in a place where wilderness is abundant I enjoy hiking, camping and nearly everything associated with the outdoors.

Laurent Drissen

l'Université Laval

A figure showing a 255 nm image with bright hot horizontal branch stars (larger open circles) is a low resolution version of a figure in the reference above. A brief description about research on M 80 describes these blue stragglers.