Media Memo

Johns Hopkins University astrophysicists working with the Astro-2 observatory report getting extremely sharp spectrographic data from a special type of galaxy that varies in luminosity is now emitting exceptionally brightly.

On the sixth day of the Astro-2 mission -- only one-third of the way through the orbiting astronomy expedition -- Johns Hopkins University scientists already have collected more data than they did during the entire nine-day Astro-1 mission, in 1990.

"It feels like we are drinking from a fire hydrant," said Arthur Davidsen, principal investigator of the Hopkins Ultraviolet Telescope project. HUT is one of three telescopes making up the Astro-2 observatory, on the space shuttle Endeavour. The mission is planned to last 16 days.

On Tuesday morning, the HUT team was lucky to capture a Seyfert galaxy in an unusually bright phase. The galaxy, called NGC 4151, is 54 million light years away. Seyfert galaxies vary in brightness. NGC 4151 is presently about five times brighter than it was during Astro-1 -- enabling scientists to gather exceptionally crisp spectrographic data, Dr. Davidsen said.

"It's really remarkably bright right now," said Dr. Davidsen, a professor in the Johns Hopkins Department of Physics and Astronomy. Seyfert galaxies contain very bright centers, called active galactic nuclei. Astrophysicists believe the galaxy's center harbors a supermassive black hole, an object so massive not even light can escape its gravitational attraction.

The HUT team has observed NGC 4151 three times so far and scientists plan to repeat the observations every two days. On Tuesday, its brightness had increased by 10 percent compared with previous observations, earlier in the mission, said Gerard Kriss, HUT's project scientist, who specializes in active galaxies.

Astronomers expect its brightness to increase even more by the next observation, he said.

Scientists have detected "very unusual characteristics of NGC 4151," he noted. HUT's spectrograph has picked up what appears to be the outer portion of a disc of gas slowly spiraling into the black hole, in the center of the galaxy, said Dr. Kriss, an associate research professor. The gas absorbs light shining through it, producing "absorption lines" in the spectrograph data.

The disc of gas is possibly an atmosphere located above a hypothetical ring of opaque material scientists believe may exist in active galaxies.

"It's really thrilling," Dr. Kriss said. Only HUT can observe the short wavelengths ideal for the research. The astrophysicists will analyze the data after the mission to learn more about what makes the galaxy's core behave the way it does.

"We are trying to learn more about active galaxies in general," Dr. Kriss said.

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