Neighboring Galaxy

To think that there is more outside of our own planet is strange enough, but to think there are whole other galaxies is just ridiculous!  The Andromeda Galaxy is our "neighboring" galaxy; it is the closest major (or large) galaxy to us.  Our home part of the Universe is the Milky Way Galaxy and a couple million light years away is the Andromeda Galaxy.

(Actual picture taken by Robert Gendler, image from http://www.pbs.org/seeinginthedark/astronomy-topics/andromeda-galaxy.html)

Andromeda is a spiral galaxy (as shown above), similar to ours, rotating in free space.  Often referred to as M31 (or Messier 31, named after astronomer Charles Messier), it contains about 1 trillion stars, a number seemingly impossible to understand.  This is a vast amount more than we have in our own galaxy.  The Andromeda Galaxy is so bright it can actually be seen with the human eye at night, if you know where to look.


Astronomers have attempted to measure the dimensions and gather other statistics about this galaxy for a long while.  Recently scientists have used an eclipsing binary star of the Andromeda Galaxy to find the distance to Andromeda.  The binary star is a system of two stars that rotate around a central point (the center of mass) causing one another to eclipse each other from an outside reference frame.  Through this study, the sizes of the stars were found.  Combining this new data with the temperature of the stars, they found the distance to be a little over 2.5 million light years away.


The Andromeda Galaxy is quite large; it has a disk-like structure that extends a distance of 220,000 light years.  The structure of the galaxy is actually warped by the gravitational field of its own nearby (smaller) galaxies causing it to not be a perfectly flat spiral.  The mass of this enormous galaxy has been found to be 1.2 trillion times that of the Sun (solar masses), smaller than that of the Milky Way Galaxy (having a mass of 1.9 trillion solar masses), yet still a substantial amount.  At the center of this spiral there is an extremely dense cluster of stars that show a high level of luminosity.  The luminosity of the galaxy is estimated to be about 3.1e10 times that of our Sun.  However, with the increase in star formations of the galaxy, this number can vary.

(Picture of center of M31 showing high luminosity, image from http://www.universetoday.com/61779/andromedas-double-nucleus-explained-at-last/)

The Andromeda Galaxy is both beautiful and amazing; it is massive and bright, strange and mysterious.  Proof of this outstanding discovery brings the question, if other galaxies exist in our universe, what else is out there? 

(video from http://www.youtube.com/watch?v=HWxBTHVhc3I)