University of Maryland at College Park
Department of Astronomy - Stellar Astronomy

Recent Explorations

• synthetic stellar spectra
• planetary nebulae
• stellar atmospheres
• nucleosynthesis

What happens to a star as it dies? Most stars end their lives as compressed, dim objects known as "white dwarfs." But before they can reach this state, they must slim down by throwing their excess mass into space, forming what are called "planetary nebulae." These beautiful clouds of ionized gas, enriched with chemical elements formed deep in the star's interior, hold many secrets of the late stages of stellar evolution. Maryland astronomers have played a leading role in probing these nebulae with the Hubble Space Telescope and in constructing computer models of how such gas clouds respond to the star's ultraviolet radiation.

Computer modeling is also essential in exploring the composition of stellar interiors and their atmospheres. By studying the light emitted from a star, astronomers can find out what elements exist. These calculations are essential in order to solve fundamental problems in astronomy, such as the ages of globular clusters, which place limits on the age of the Universe.

Since using line spectra to determine the composition of individual stars works so effectively, the Stellar Astronomy Group has been applying this technique to determine the spectra and colors of galaxies. Using stellar interior calculations to give the relative number of stars of different kinds, galactic models can be made by combining their individual spectra and colors. This important information will allow researchers to find the ages and compositions of individual galaxies.

Photo Caption:

This image of NGC 6543, the "Cat's Eye Nebula," was taken by Maryland astronomers using the Hubble Space Telescope. It depicts the death of an ordinary star--the white point at the center--which has just cast off the glowing red clouds of hydrogen gas.

Photo Caption:

Detailed spectra of the Sun and the star, Arcturus. The upper spectrum is that for the Sun--the top spectrum is calculated, the lower observed. The lower panel shows the same for Arcturus.

Rob Cavallo

"One of the most exciting experiences I've had at Maryland was the opportunity to give a talk at CalTech at a symposium on nuclear astrophysics. I was surrounded by all these preeminent scientists, whose books and papers I had read, and there I was chatting in front of them.... Most of them were observers and I'm a theorist, so it was kind of neat to be able to explain to them what they were looking at.

When I was a young kid, I used to look up in the sky and ask my older relatives questions about what the stars were. No one could ever answer my questions. As I grew older, my curiosity also grew and I began to find the answers myself. I am finally at the point where I am the one who gets to answer the questions for which there have never been any answers."

There is also a page of miscellaneous information about the Astronomy Department.