NGC 1232: A Colossal Cosmic Crash

Narrator (April Hobart, CXC): If the majestic pinwheel structure of this galaxy wasn't beautiful enough, the pink halo gives this photograph a magical finish. Yet, what we're actually seeing here is pretty violent. In this picture, a galactic collision is taking place between the grand spiral galaxy and the tiny dwarf galaxy that you can see to its left. The pink mist is actually a huge cloud of gas, burning at millions of degrees Celsius, which forms when these galaxies clash! This cloud is mostly invisible to our eyes but the gas shines brightly with high-energy X-ray light at extremely high temperatures.

Near the "head" of this comet-shaped fog, you can see an area with a group of very bright stars. The energy of the crash may have caused a boom of star formation here. Powerful explosions from dying stars and cosmic gale-force winds coming from hot, bright stars help keep the cloud shining brightly with X-rays.

As for how big this cloud is, it's difficult to measure. We struggle to determine the shape of distant cosmic objects. We only have flat, 2-dimensional images to work with and it's not like we can fly behind them to take a look! Is this pink mist thin and shaped like a pancake? Or is it thicker, like a fat rain cloud? Until we know the shape, we can't be sure just how big it is. If it is thin like a pancake then it will have 40,000 times the mass of our Sun. If it is more spherical, it would be more like 3 million times as massive as our Sun!

Return to Podcasts

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

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.