Is The Milky Way More Than Your Typical Galaxy: #1 Morphological Classification

Introduction

Thanks to the ongoing Satellites Around Galactic Analogs (SAGA) Survey scientist have began making monumental discoveries about the Galaxies in the close proximity to the Milky Way.

Historically, the Milky Way Galaxy was assumed to be a fairly ordinary galaxy. Under the basis of this assumption, we have used the Milky Way to generalize the characteristics of all spiral galaxies. However, as we continue to learn more about our the universe we are coming to the realization of just how intricate and unique galaxies really are [1]. Still, Cosmologist use constantly looking to compare similar galaxies to help them quantify their similarities.

Please join me in exploring our Universe as we seek to determining whether or not the Milky Way is anything more than the average galaxy.

Unfortunately, the studies coming out of SAGA are still in early stages of their development [2]. I think it would only be proper to wait for a more complete data set before posting about their discoveries. Here is one of the articles and their main site for anyone who is interested:

http://iopscience.iop.org/article/10.3847/1538-4357/aa8626
http://sagasurvey.org

While we wait, my first few post will focus on painting a comprehensive picture of our current knowledge.

This post is about how we categorize galaxies and some of the distinctions of the Milky Way we already know of.

Morphological Classification

The Milky Way belongs to a large class of galaxies know as spiral galaxy along with around two thirds of the galaxies we have ever observed [3].

As galaxies develope they tend to take on increasing complexe shapes and are classified based on their progression into some truly amazing shapes. Below is a visual depicting the possible scenarios for how a spiral galaxy could develop:

The Milky Way is classified as a Sb galaxy but as we will see is much more special.

Barred Spiral Galaxies

A barred spiral galaxy is named for its distinctive strip running through its center where the majority of its light it emitted from. Evolving into a barred galaxy is a natural progression and around two thirds So, Sa and Sb spiral galaxies are barred galaxies.

Here is the a very clear example of a barred galaxy:

Occasionally, a barred galaxy can can also develop a secondary bar. These secondary bars can be significantly smaller than the first and do not seem to share any defining characteristics making them very difficult to categorize [4]. The Milky Way just so happens to be one of these galaxies and is part of a select group of just 13% of galaxies.

Below is an example double barred galaxy with an overlay highlighting the secondary bar:

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If you have any questions or know anything you would like to add feel free to do so in the comments! Or if you have any suggestions on how I can improve I would love to hear them!

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Work Cited:
[1] http://iopscience.iop.org/article/10.3847/1538-4357/aa8626
[2] http://sagasurvey.org
[3] https://en.wikipedia.org/wiki/Galaxy_morphological_classification
[4] https://arxiv.org/abs/0908.0909