Meet: Kevin Hurley

Research Physicist
University of California

I am a research physicist at the University of California, Berkeley, Space Sciences Laboratory. I have been working here since 1987. I specialize in building experiments which fly on spacecraft and return data on cosmic gamma-ray bursts.

Right now, I am getting data from an experiment which I built and flew on the NASA-ESA Ulysses spacecraft, as well as from experiments on the NASA Wind spacecraft, the NASA Near Earth Rendezvous spacecraft, which is orbiting the asteroid Eros, and the Italian BeppoSAX spacecraft.

What I do

Since 1977, I and my colleagues have been dreaming up experiments to measure gamma-rays. Gamma-rays are like X-rays, only more energetic. Think of them as X-rays on steroids.

Although they are very energetic, they do not penetrate the Earth's atmosphere, and you need to study them from space. Once we have a good idea, we propose it to a space agency, and get the funding to build and fly it. When the experiment has been launched, we get data back from it for several years. I have been involved in projects which were launched on Russian, European, and U.S. missions, some to Venus, others to Mars, and one past Jupiter.

Right now, besides the Ulysses mission, I am working on two other projects. One is HETE-II, the High Energy Transient Explorer, which will be launched in October 2000, and Swift, which will be launched in 2003.

When I started working in this field in 1977, gamma-ray bursts were one of the most mysterious phenomena in all of astronomy and astrophysics. They last about 10 seconds, and they come from any part of the sky about once a day. You can't predict where they will occur. Since 10 seconds is not very long, we have always wanted to find out if the sources of gamma-ray bursts had some kind of long-lived emission which we could study with telescopes, on the ground. To do this, we needed to know their positions very precisely.

The way we got them was to fly 3 or 4 spacecraft, observe the time of arrival of the burst at each spacecraft, and use this information to triangulate the position of the burst. It's a good method, and it can be quite accurate, but it takes several spacecraft to do it, and the data aren't available right away. The two projects which I am working on now, HETE-II and Swift, will overcome this problem by finding the locations of the bursts on board a single satellite, using a kind of X-ray camera.

Today, we know a lot more about these bursts. We have found that they originate in distant galaxies far, far away. They are almost at the edge of the observable Universe, in fact. They are probably emitted by giant stars which explode when they reach the ends of their lives. In any case, they are the most powerful explosions in the Universe, which makes them interesting to study. But there are still a lot of questions left to answer, such as:

1. How far away can we detect these bursts?
2. What kind of galaxies do they come from?
3. What kind of stars produce these bursts?
4. Could bursts be harmful to life on other planets?