A Seyfert Galaxy


NGC 5793Carl Seyfert was an interesting fellow. Back in the ’50s when I was a kid growing up in Nashville, he was Director of the Dyer Observatory at Vanderbilt University. I met him through the local astronomy club associated with the Nashville Children’s Museum. He was well known around town because he moonlighted as the weatherman for WSM-TV. He was known in astronomical circles for his research on a class of galaxies.

Those galaxies have incredibly luminous centers that we believe are caused by supermassive black holes—black holes that can be billions of times the mass of the sun—pulling in and swallowing gas and dust from their surroundings. NGC 5793 is a Seyfert galaxy over 150 million light-years away in the constellation of Libra.

This Hubble image is centered on NGC 5793. This galaxy is of great interest to astronomers for many reasons. For one, it appears to house objects known as masers. Whereas lasers emit visible light, masers emit microwave radiation. The term “maser” is an acronym of Microwave Amplification by Stimulated Emission of Radiation. Lasers emit visible light; masers emit microwave radiation. Maser emission occurs when particles absorb energy from their surroundings re-emit the energy in the microwave part of the spectrum. Naturally occurring masers such as are found in NGC 5793 can tell us a lot about their environment; we see some types of masers in areas where stars are forming. In NGC 5793 there are also intense mega-masers, thousands of times more luminous than the sun.

Image Credit: NASA

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