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Closing in on Quasars

A quasar and its surrounding galaxy

Our galaxy, the Milky Way, is quiet and calm. But other galaxies are loud and boisterous. An example is the class of galaxies known as quasars. Their cores contain black holes that are millions or billions of times as massive as the Sun. Disks of superhot gas, known as "accretion disks," encircle the black holes. A typical quasar accretion disk is perhaps as wide as our solar system, yet it produces as much energy as an entire galaxy of normal stars. Sarah Salviander is using McDonald Observatory's 107-inch (2.7-meter) Harlan J. Smith Telescope to study several bright quasars. Her observations are helping astronomers compare mathematical models to the structures of real quasar accretion disks.

Two for the Price of One

A distant binary quasar.

While observing quasars, Greg Shields and colleagues had a "remarkable stroke of luck." They were using a spectrograph aboard Hubble Space Telescope to study what appeared to be a single quasar. But the astronomers found that it was really two quasars, not one. This binary-quasar system is unique because the two quasars are separated by only 7,000 light-years. This indicates that the two quasars are in the core of a large galaxy that was born when two smaller galaxies merged. This rare binary quasar is giving Shields and his colleagues the chance to study the characteristics of these objects, and to learn more about conditions when they took shape.

Nurseries for Supermassive Black Holes

Simulated orbits around a black hole.

Texas astronomer Karl Gebhardt is shedding light on how galaxies and black holes form and how they change over time by studying some of the most massive galaxies in the universe. Gebhardt is using the Hobby-Eberly Telescope to take detailed observations of candidate galaxies. The most massive galaxies should contain the most massive black holes in their cores. Studying these large galaxies reveals details about the environment in which supermassive black holes grow. It also will reveal how these monstrous black holes affect the evolution of their host galaxies.

This document was last modified: October 19 2009.