NGC 602: The Galactic Empire

Narrator (April Hobart, CXC): Our galaxy, the Milky Way, is more than just a giant barred spiral containing hundreds of billions of stars. It's also the centre of a colossal empire and rules over about 20 smaller galaxies that orbit around it, similar to the way our Moon orbits the Earth. The shining stars and glowing arcs of gas in this picture reside in one of these subjects: a dwarf galaxy called the Small Magellanic Cloud.

If you live in the Southern Hemisphere or near the equator, you may have noticed two bright but blurry clouds in the dark night sky. The smaller of these clouds is the Small Magellanic Cloud, one of the Milky Way's so-called 'satellite galaxies'. It is a dwarf galaxy, meaning that it contains far fewer stars than galaxies similar to our own. While the Milky Way is made up of about 300 billion stars, the Small Magellanic Cloud has just a couple of billion.

On a cosmic scale, this galaxy is extremely close by. Moving at the fastest speed known in the Universe (the speed of light), it would take less than 200 thousand years to travel there from Earth.

Being so close to us, the Small Magellanic Cloud offers astronomers an opportunity to study phenomena that are difficult to examine in more distant galaxies. This picture shows an area of the galaxy called the 'Wing'. It contains three star clusters that astronomers have been studying recently to find out how young stars are born.

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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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