Sagittarius A* in 60 Seconds

Narrator (April Hobart, CXC): Scientists have long known that the giant black hole at the center of the Milky Way is a particularly poor eater. Unlike some of its more distant galactic cousins including quasars, the Milky Way's black hole doesn't seem to be consuming much material, and, as a result, it is remarkably dim in X-ray light by comparison. To find out why our black hole behaves as it does, scientists used Chandra to observe the black hole - known as Sagittarius A* -- for over five weeks worth of time. This is one of the largest amounts of time that Chandra has ever looked at the same object. Sagittarius A* is a black hole with about 4 million times the mass of the Sun. At just 26,000 light years from Earth, Sagittarius A* is one of very few black holes in the universe that's close enough where we can actually witness the flow of matter nearby. The researchers found out that Sagittarius A* actually consumes less than about 1% of the material it has available to it. While they are still working out the details of how and why the black hole is so finicky, astronomers now have a new piece of the puzzle thanks to these new X-ray data from Chandra.

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HD 189733: NASA's Chandra Sees Eclipsing Planet in X-rays for First Time

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Narrator (April Hobart, CXC): HD 189733b: An exoplanet in orbit around a star about 63 light years from Earth. It has been nearly two decades since the first exoplanets – that is, planets around stars other than our Sun – were discovered. Now for the first time, X-ray observations have detected an exoplanet passing in front of its parent star. The observations, made by NASA's Chandra X-ray Observatory and the European Space Agency's XMM-Newton Observatory, took advantage of the alignment of a planet and its parent star in HD 189733. This alignment enabled the observatories to observe a dip in X-ray intensity as the planet moved in front of, or transited, the star. This technique is the one used so successfully at optical wavelengths by NASA's Kepler telescope. In earlier studies using optical light, astronomers discovered that the main star in the HD 189733 system had what is known as a "hot Jupiter" around it. This means the planet is about the size of Jupiter, but in very close orbit around its star. The planet – that has been named HD 189733b -- is over 30 times closer to its star than Earth is to the Sun, and goes around the star once every 2.2 days. The new X-ray data suggest that this planet has a larger atmosphere than previously thought. This, in turn, may imply that radiation from the parent star is evaporating the atmosphere of HD 189733b more quickly than expected. The results on HD 189733 demonstrate how we need information from many different telescopes that detect different types of light to get a fuller picture of these mysterious worlds that we are now able to explore.

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