What causes the violent activity in the center of some galaxies? The answer remains one of the outstanding puzzles of modern astronomy. We do know that in some galaxies, the activity is powered by hot, massive stars which are formed in a so-called starburst. In others, there is no sign of hot stars; however, astrophysicists believe the power source is gravitational accretion by a supermassive (a million to a billion solar masses) black hole. The energy released by this accretion gives rise to a range of different active galaxy types, including Seyfert galaxies, radio galaxies, LINERS, BL Lac objects, and quasars.
The Extragalactic Group conducts extensive, multiwavelength observational efforts aimed at determining the origin of nuclear activity in galaxies and the physical processes involved. Observations are being made with telescopes in space, such as the Hubble Space Telescope, ISO, ROSAT, and the ASCA X-ray satellite, and on the ground, especially with BIMA and other large radio and optical/infrared telescopes. Recent emphasis has included measurements of the masses of black holes, studies of water vapor masers in the circumnuclear accretion disks, imaging and spectroscopic studies of the ionized gas and underlying stellar populations, and determination of the effects of nuclear activity on the surrounding environment, including the intergalactic medium. An effort has also been made to define the gaseous size of nearby active and normal galaxies and relate these observations with what is currently known of the more distant Universe.
![[Photo of a NGC 3079]](starburst.gif)
![[Photo of Scott Miller]](miller.gif)
"I worked at Goddard my first summer here looking at X-ray data from a nearby galaxy, NGC1313. There are three luminous sources, two of which remain unknown. I turned that work into my second-year research project and now I'm trying to get it published in The Astrophysical Journal.
I've taught for five semesters and it's something I enjoy very much. It's the greatest pleasure when you see that look on students' faces when a concept suddenly becomes clear. Astronomy excites me so much; I try to pass on that excitement to my students.
I think the atmosphere within the department is one of the best things about my experience here. The class size is perfect, and we tend to be a pretty close-knit group. Professors are always there for you. Many of them don't have formal office hours--they just say to drop by. It's a good atmosphere for learning."