APOD 4.4

For this week's APOD, I chose the picture called The Antennae, uploaded on April 29.  It is about the collision of two large galaxies, in the constellation Corvus, which was one of our class constellations this week.


Corvus is a southern constellation, and is about 60 million light-years away from us.  Although the galaxies themselves collided, the stars didn't.  NGC 4038 and NGC 4039 were the names of the stars included in this huge event, lasting many of years after.  The stars usually don't collide because galaxies are mostly empty space, and no matter how bright they are, stars can only take up a rather small portion of that space.  Moreover, stars are formed in the process.  There are large clouds of molecular dust and gas that spur energetic episodes of star formation near the heart of the collision wreckage.  The galaxy shown in the picture spans about 500 thousand light years across.  It looks like an Antennae, and is so rightly named, because of the extensions and arching structures of the galaxy.  Star clusters and other matter were thrown far from the collision scene by accidental gravitational forces.  William Herschel was first to discover the interaction of these two galaxies in 1785, and described that they were shining at around 10m4.