Meet: David Burrows

Senior Scientist
The Pennsylvania State University
University Park, PA

I am a research astrophysicist in the Department of Astronomy and Astrophysics at the Pennsylvania State University (Penn State) in University Park, PA. I have been working here since 1983. I got interested in science, math, and the space program as a kid, launched model rockets in high school as a hobby, majored in Physics in college, and was delighted to discover in graduate school that I could get a PhD launching experiments on sounding rockets. I worked on six different rocket launches in graduate school (at the University of Wisconsin), finished my PhD in 1982, and came to Penn State in 1983. I have been launching sounding rockets here since 1987.

What I do

I specialize in building X-ray instruments which fly on sounding rockets and spacecraft and measure the spectrum of X-rays from hot gas in our galaxy. I also study X-ray emission from supernova remnants, and I am currently analyzing observations of supernova remnants made with the Chandra X-ray Observatory. Most recently, I have become interested in Gamma-Ray Bursts. I am currently spending most of my time building an X-ray Telescope for the Swift Gamma Ray Burst Explorer. I would be happy to chat about any of those topics.

X-ray Astronomy and Sounding Rockets

What are X-rays? I'm not talking about the images of your bones or teeth made by doctors and dentists. Those are actually shadowgrams: images of the shadows cast by your bone structure when illuminated by a source of X-rays. The X-rays themselves are a high energy form of light. As you pass through the visible spectrum from red to blue, the energy of each photon of light increases. Past blue you encounter shorter wavelengths of light called ultraviolet light and X-rays. X-rays have enough energy to penetrate through solid matter, but they are absorbed more strongly by heavy elements like calcium than by lighter elements like carbon. This is why they are useful as medical diagnostics.

X-rays are also absorbed in the Earth's atmosphere. This is very fortunate for us, because otherwise we would be constantly bombarded by X-rays from space, but it makes it difficult for us to study these X-rays. Until the dawn of the space age, such study was impossible. In the 1950s, scientists learned that the Sun produces X-rays, but it is such a faint source that most scientists did not expect any other celestial objects to be visible in X-rays. Finally, in 1963 an X-ray detector launched into space on a sounding rocket discovered a glow of X-rays from the sky, now referred to as the Cosmic X-ray Background. This was the birth of X-ray Astronomy.

Sounding rockets have played an important part in the history of X-ray astronomy. Unlike a satellite launch vehicle, a sounding rocket does not orbit the Earth. Instead, it carries a payload in a parabolic trajectory out of the Earth's atmosphere into space. This allows us to make measurements in space at a fraction of the cost of a satellite mission, although for only a brief time (about 6-7 minutes). In the 1960's, all X-ray astronomy was done from sounding rockets. During the 1970's and 1980's, more and more of our X-ray observations were made from satellites, which offered the advantage of much longer observing times. Today, most scientific research in X-ray astronomy comes from satellite observations, but sounding rockets still have a place for instrument testing and graduate student training.