A Tour of DEM L241

Narrator (April Hobart, CXC): When a massive star runs out fuel, it collapses and explodes as a supernova. Although these explosions are extremely powerful, it is possible for a nearby star to endure the blast. A team of astronomers using NASA’s Chandra X-ray Observatory and other telescopes has found evidence for one of these survivors. This hardy star is in a stellar explosion’s debris field − also called its supernova remnant − located in an HII region called DEM L241. An HII (pronounced "H-two") region is created when the radiation from hot, young stars strips away the electrons from neutral hydrogen atoms to form clouds of ionized hydrogen. This particular HII region is located in the Large Magellanic Cloud, a small neighboring galaxy to the Milky Way. The supernova remnant remains hot for thousands of years after the original explosion occurred, and this means that it continues to glow brightly in X-rays that can be detected by Chandra. The data suggest that a point-like source in X-rays is one component of a binary star system. In such a celestial pair, either a neutron star or black hole, which is formed when the star went supernova, is in orbit with a star much larger than our Sun. As they orbit one another, the dense neutron star or black hole pulls material away its companion star through the wind of particles that flows away from its surface. If this result is confirmed, DEM L241 would be only the third binary containing both a massive star and a neutron star or black hole ever found in the aftermath of a supernova.

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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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