The next time you have a chance to look up at the night sky, bear in mind that nearly every thing you can see with your bare eyes is something in our own galaxy, the Milky Way. Of the 100 to 200 billion galaxies in the universe (some estimates put that number even higher, at 500 billion) only a handful are visible in the night sky from Earth without a telescope. Two of those, the Large and Small Magellanic Clouds, were recently the subjects of a NASA ultraviolet survey, and the agency has just released some dazzling pictures of these neighbors, just 163,000 and 200,000 light years away, respectively. Both galaxies are visible to astronomers and star-gazers from our planet's southern hemisphere.
The top image shows the galaxies as they appear in visible light. Here's each as NASA's Swift satellite saw them in ultraviolet.
Large Magellanic Cloud
Small Magellanic Cloud
Both of the images are mosaics compiled of many images (2,200 for the LMC and 656 for the SMC). The images were collected over a total of more than six days.
The two galaxies are relatively small. The Milky Way is about 10 times bigger than the LMC (14,000 light years across), which itself is twice as big as the SMC (7,000 light years across). We can see them in the night sky not because of their size but because of their proximity.
Ultraviolet detection allows scientists to see where a galaxies hottest stars and nebulae are. The survey revealed about 1 million such light sources in the LMC and 250,000 in the SMC.
Not that long ago, when astronomers looked to the sky, they wondered whether there were other planets out there orbiting nearby stars. Over the past ten years, an explosion of data and observations have shown us that not just are there planets out there but there are billions and billion of them in our galaxy alone. When we look beyond our own galaxy to the Large and Small Magellanic Clouds, they're no longer clouds at all, but smudges of hundreds of thousands distinct points of light, and maybe some (many?) of those stars have planets orbiting them too.