Galaxies are vast accumulations of gas, dust and billions of stars, bound by gravitational forces, formed after the Big Bang. And even though astronomers are still not 100% sure about the way galaxies were created and have different theories, and one thing is for sure: they are massive, and their gravity is strong.
How many types of galaxies are in the universe?
There are three main types of galaxies, spiral, irregular and elliptical. Spiral galaxies, such as our Milky-Way, contain a central bulge surrounded by a flat, rotating disk of stars. Astronomers say that they make out most of the galaxies discovered by now.
Irregular galaxies, as their name suggests don’t have a regular shape with no spiral arm or a central bulge. And even if they might have formed after violent collisions of two or more galaxies, they are amongst the smallest ones.
Finally, elliptical galaxies don’t have swirling arms and have a smoother, rounder shape with practically featureless brightness and have large sections of old stars.
Hubble Space Telescope imaged Messier 49, an elliptical galaxy
That is an elliptical galaxy discovered in 1771 by a French astronomer, the first of the Virgo galaxies Cluster observed by astronomers, measuring 157.000 light-years across.
Just like the Milky Way, at the center of Messier 49 is found a supermassive black hole that has the mass of over 500 million Suns, which was identified thanks to X-rays discharging.
Unlike other elliptical galaxies, Messier 49 is brighter, hosting around 6000 globular clusters which are 10 billion years old. Star formation has stopped in this galaxy for more than 6 billion years ago. Considering that it has a yellow light, it which suggests that it contains stars that are older and redder than our Sun.
Andre Blair s is the lead editor for Advocator.ca. He holds a B.A. in Psychology from the University of Toronto, and a Master of Science in Public Health (M.S.P.H.) from the School of Public Health, Department of Health Administration, at the University of North Carolina at Chapel Hill. Andre specializes in environmental health, but writes on a variety of issues.