The Milky Way Galaxy has a black hole at its heart -- an object called Sagittarius A* (pronounced A-star). We can?t see it visually, but radio astronomers can easily spot it. A group led by Dr. Shep Doeleman at MIT?s Haystack Observatory made a startling measurement of the accretion disk around Sagittarius A*. In this edition of Astronomy Behind the Headlines we talked with Dr. Doeleman about his team?s discovery.

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On July 19, 2009, Australian amateur astronomer Anthony Wesley spotted a dark-colored scar high in the clouds over Jupiter?s southern polar region. It looked like the scars left behind by Comet Shoemaker-Levy 9 when its shattered fragments crashed into Jupiter in the summer of 1994. Dr. Heidi B. Hammel is one of the astronomers who have studied the aftermath of this latest collision to learn about how Jupiter?s atmosphere responds to such collisions. In this episode, Dr. Hammel discusses what her team learned from their observations of the collision site using Hubble, Gemini, and Keck cameras.

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When humans return to the Moon to explore and live on its surface, those future lunar inhabitants will need safe habitats and plenty of water. As it turns out, the Moon may have all the water we need, locked away in ice deposits at its poles. Today, NASA?s Lunar Reconnaissance Orbiter (LRO) and the Lunar Crater Observation and Sensing Satellite (LCROSS) are allowing scientists to search for water at the lunar south pole. In this episode, we hear about this water-hunting expedition from Brian Day, the education and public outreach lead for the LCROSS mission.

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In this episode with guest Dr. Peter Jenniskens of the SETI Institute, we explore those things that go "flash" in the night sky -- and often are romantically called "shooting stars". In reality, of course, they're not stars but "meteors". Now, meteors are not part of our weather, as people used to think, but are usually caused by pieces of rock that arrive from space at incredibly high speeds and collide violently with the air. These meteoroids can be as small as a grain of sand all the way up to a good-sized boulder and often come from streams of dust particles created by comets as they travel around the Sun. We'll also discuss other forms of cosmic debris, such as asteroids.

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This episode with guest Dr. Chris McKay from the NASA Ames Research Center talks about astrobiology and the search for life in the universe. Living things have been found in very extreme environments on Earth, like hot springs, or near underwater volcanoes, or hidden beneath the Antarctic ice pack, or even inside rocks. Could life exist in those same kinds of places on other planets? When we look for signs of life on other worlds, what would we look for? How do we search it out? And, how would we know if what we find is caused by living things -- or some other physical process?

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