Coma Cluster: Growth of the Coma Colossus

Narrator (April Hobart, CXC): This picture shows the very large, very distant and very gassy Coma Cluster. It's a giant cluster of over 1000 galaxies that are all bound together by gravity. If you take a close look, you can make out the yellow-white shapes of galaxies scattered across the picture. The pink blobs show arms of multi-million degree gas, hot enough to cook your lungs in half a breath.

All big clusters of galaxies contain this very hot gas. The gas sends out lots of powerful X-rays because it's so hot, and these are what we can see in pink here. You can't see X-rays with your eyes, so astronomers have coloured them in pink. This gas is actually a very helpful tool for us, because the amount of material in the cluster can be measured using just the temperature of the gas! The hotter the gas, the more material there is!

Our Galaxy is also part of a group of galaxies, called the Local Group. Our cluster is also filled with gas, but it's so spread out that we don't see it when we look into the night sky. And because the Local Group is much smaller than the Coma Cluster, the gas around our galaxy isn't nearly as hot.

The gas in this picture also tells another story. The shape of these pink clouds and how they are spread throughout the cluster give us clues into how the Coma Cluster has grown. They show us that smaller groups of galaxies and smaller galaxy clusters have crashed and combined over time. The final result is the colossal Coma Cluster we see today, one of the biggest structures in the entire Universe!

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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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