He is a co-investigator for the Infrared Space Observatory , an orbiting telescope launched in November 1995 by the European Space Agency. The observatory, which contains a telescope cooled by liquid helium, is able to make very sensitive observations at infrared wavelengths. Much of the infrared emission from a normal galaxy comes from dust grains heated by newly formed stars in the galaxy s spiral arms. By looking at the variations in the infrared properties of different galaxies, Dr. Joseph studies how the rate of new star formation in galaxies depends on such factors as mass distribution and gas content. Given the large diameters of galaxies and their relatively close separation in space, it is inevitable that galaxies sometimes collide with each other.
Gas falling toward the nuclei of colliding galaxies can trigger vast bursts of new star formation.
In an AGN, energy is released as matter spirals toward a massive black hole at the nucleus of one or both of the galaxies. Part of the energy is emitted as electromagnetic radiation that can be directly detected by telescopes, part goes into heating and accelerating the gas that surrounds the black hole, and part may be focused into jets that eject radio-emitting plasma clouds vast distances into intergalactic space. Quasars, the most powerful objects in the known universe, are examples of AGNs. Several astronomers at UH are trying to understand how AGNs are produced and why some galaxies contain starbursts and some contain AGNs. Josh Barnes simulates galaxy collisions using a supercomputer to compress 100 million years of star motions into a few minutes.