Galaxies Compared to Ours

For this conceptual objective I am asked to compare other types of galaxies to our Milky Way. For this I’m going to explain the different types of galaxies that we’re aware of and then relate this all to the recent discovery of two new galaxies by researchers at the University of Utah.

So, there are four major types of galaxies that astronomers have cataloged. These galaxy types are: Spiral, Bar Spiral, Elliptical, and Irregular Galaxy. Along with these types, there is also Hubble’s System of galaxy classification. This system (image below) give a more detailed idea of what the galaxy in question looks like.

This image is of Hubble’s System, E stands for Elliptical, S (spiral), and SB (Spiral Bar). Missing from this diagram is the Irregular galaxy that would appear to the far right.

The most recognizable galaxy is the Spiral Galaxy, Sa. This is the galaxy that most people think of when they hear the word, a bright center with well-defined arms spiraling out into a disk shape before fading into the black of space. Spiral galaxies are large with great amounts of dust and gas obstructing a lot of the light within. The innermost part of these galaxies harbor old stars while the outer reaches of the arms are host to new star births. Of course, these are in no way set rules for the spiral galaxy, all galaxies have their exceptions to these traits. An artist rendition of a spiral galaxy is located below.

The next most recognizable galaxy is the Spiral Bar Galaxy. It is estimated that our galaxy is an SBb galaxy, a Spiral Bar galaxy with not-so tight spiral, old stars near the center, new star formation near the outermost regions. The only major difference between Spiral Bar galaxies and Spiral galaxies is the shape of their center, whereas the Spiral galaxy spirals into the center, Spiral Bar galaxies (as simple as it sounds) spiral into a bar shape where the supermassive black hole in the center. The image below may better help understand just how they appear.

The less-known type of galaxy is the Elliptical Galaxy. This type of galaxy is small, with no regions of new star development they’re mostly old dim stars. Unlike the other two types of galaxies the Elliptical galaxy does not have a disk shape, instead these galaxies are more spherical. But, much like the other galaxies Elliptical galaxy’s centers are obscured by a large a

The last and, in my case, least known type of galaxy is the Irregular Galaxy. These galaxies have no definite shape, are usually small, and located near larger galaxies. Irregular galaxies have plenty of active star formation but even with this they are rather dim and because of this, not very much is known about them because they are hard to spot.

The discovery made by researchers at University of Utah of two new galaxies is a rather recent discovery.  The type of galaxy isn’t directly stated, rather the galaxies discovered are described as Dwarf Galaxies. These are explained to be ultra-compact galaxies that have pretty much been eaten up by the black hole at the core. Of course this is obviously unlike our galaxy. As we learned in class, our galaxy is over 100,000 light years across, and roughly 2,000 light years thick. These Dwarf Galaxies are described as “..just the cores left behind” containing about “100 million to several billion stars…” whereas our galaxy contains over 300 billion stars that we’re aware of.

I enjoyed this article but wish that it would have had a bit more descriptions on the galaxies themselves. VUCD3 and M59cO are so small and bright that the astronomer that originally viewed them was unaware that they were black holes, which is interesting because scientists usually have a hard time finding black holes for the exact opposite reason. Also, we didn’t talk about Dwarf Galaxies in class so I thought it was interesting to add a new type to my personal catalog.


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