G1.9+0.3: The Big Explosion No One Saw

Narrator (April Hobart, CXC): About once or twice every 100 years, a gigantic nuclear bomb detonates in our Galaxy. In just a few short weeks, it blasts out as much energy as our Sun will in its entire lifetime! This powerful explosion is called a 'supernova', and it is the result of a star dramatically ending its life.

The most recent supernova in our galaxy, the Milky Way, happened just over 100 years ago. But, unfortunately for our great-great-great grandparents, the explosion was hidden behind thick clouds of gas and cosmic dust, far away from the Earth. So they couldn't witness this very rare sight. Because of this cosmic dust, it wasn't until 2008 that a group of astronomers finally stumbled upon the remains of the obliterated star, which you can see in this photograph.

Normally, when a supernova like this happens, the star's material is blown out evenly in all directions. This leaves behind a cloud that is more or less neat and symmetrical, but the object in this picture doesn't follow a neat pattern. Most of the star's material was blasted towards the top of the picture, and it's still travelling in that direction extremely fast. From these clues, astronomers have deduced that this must have been an unusually energetic and messy supernova explosion!

As far as we know, the last supernova in the Milky Way was over 100 years ago. If they happen on average every 100 years or so, another one should be due really soon. Keep your eyes on the skies and you might be the one to spot it first!

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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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