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Nolan Walborn

picture of Nolan Walborn
I'm a staff astronomer at the Space Telescope Science Institute. In principle I spend half my time working on some aspect of the Hubble Space Telescope mission, and the other half doing my personal scientific research. At the moment I'm on a sabbatical year so I'm doing research almost all the time, but previously I was the Head of the Science Program Selection Office.

You may wonder who gets to use the HST and how they are selected. Well, the job of SPSO is to manage just that aspect of the HST mission. Once a year, a call for proposals to use HST is sent out to the worldwide astronomical community, with instructions and a deadline by which to respond. Many astronomers work very hard to prepare high-quality proposals to observe the celestial targets they are interested in with HST, because no other instrument can do what it does, and they know that many more people would like to use it than can be accommodated in the available time.

For instance, during the last selection cycle over 1000 proposals were received, but only about 300 could be accepted. The review and selection is done by specialist committees in all the subfields of astronomy, made up of members of the worldwide community, i.e. the "peers" of the proposers themselves. This process is called peer review, and it is the best way to try to make sure that the best proposals scientifically are selected. The last time there were eleven specialist committees, followed by a final allocation committee including the eleven specialist chairpersons to integrate the separate recommendations and fit them into the available time. Approximately a hundred astronomers are involved in these meetings. Their organization and management is the job of SPSO, and it is very important because it determines what science is done with HST, and how the community feels about those decisions.

My research specialty is the study of hot, massive stars, which contain between about 10 and 200 times the amount of material making up our Sun. These stars are much brighter and have shorter lives than the Sun, just a few million years as compared to 10 billion for the latter, because their higher internal temperatures cause the nuclear reactions which power them to proceed much more quickly. These nuclear reactions change one chemical element into another with a release of energy; they not only allow the stars to be stable and shine during their lifetimes, but they also build up the supply of heavier chemical elements in the universe, out of which everything including ourselves is made up.

At the end of their lives, when their nuclear fuels are used up, massive stars undergo a violent collapse and then explosion called a supernova, which blasts the newly made chemical elements back out into space, where they may find their way into the composition of a new generation of stars and planets. In fact, the atoms in our bodies were made in just this way! So the study of massive stars is very important for understanding the structure and evolution of the universe.

I study their spectra, that is the light they emit from their surfaces spread out by an instrument such as a prism or grating according to its wavelength or color, like a rainbow. The details of a spectrum can tell us about the physical conditions of the object which produced it, such as temperature, pressure, chemical composition, and even the speed and direction of its line-of-sight motion! For example, massive stars are losing their outer layers by an expansion called a stellar wind, which for most stars can be observed only in the ultraviolet wavelengths of the spectrum that are blocked by the earth's atmosphere and so can be observed only from space.

Massive stars also like to form in compact groups, which cannot be resolved from inside the earth's atmosphere because of the disturbing effects of the air's motions on their images; with HST I can observe the spectra of ten stars in a group which looks like a single bright star from the ground! Like in most areas of astronomy, HST enables observations and discoveries about massive stars which cannot be made with any other existing instrument.

Modern astronomy is really a field of physics: astrophysics. I was studying physics and mathematics in college. Then I went to a summer institute in space sciences at a university between my junior and senior years, which motivated me to apply to graduate school in astronomy and astrophysics.

The best thing is being able to do research, to investigate the unknown and find something new which no one knew before. The program selection work is interesting because one has an overview of all the frontier science being proposed for HST, as well as that which is selected. The least enjoyable aspect occurs when people are unhappy with and complain about the results of the selection process; astronomers are people, too! Then we have to investigate the complaints, which sometimes are valid but more often not. So a few people have to stay unhappy until the next proposal opportunity rolls around.

I think it's important to be interested in what's around you and to want to understand something about it. I remember being a picture collector as a child, making scrapbooks of whatever I happened to be interested in at the time. I remember it being birds, cats, cars, airplanes, and even space for a while! I also read a lot of books and magazines on just about any subject. I think one can learn a lot more from reading than from TV, except for nature and art programs on public television! By reading, one also learns how to communicate in writing in both directions, comprehension and expression, which may even be related to learning how to think. TV doesn't do much at all for you in that regard! Then in high school and college, it's important to emphasize physics and math to prepare for a career in astronomy. Computer skills are also very important in modern astronomy.

I was influenced by three science teachers who made their subjects interesting and exciting, all of whose last names began with M! Dr. Naum Mittelman, American Community High School, Buenos Aires, Argentina. Dr. Richard Mara, Gettysburg College. Dr. William Morgan, Yerkes Observatory, University of Chicago.

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