Galaxies are the largest single object in the universe and each one contains over a trillion stars "in a single gravitational bound system." While the universe is large and most galaxies are very far apart, it is actually quite common for galaxies to group together in clusters. it is also common for these galaxies to collide with each other which results in the creation of a whole new galaxy. It was news to me to learn that there is a separate branch of astronomy devoted just to the study of colliding galaxies. Astronomers have observed that starbirth is often triggered when galaxies merge together.
Two of the most famous galaxies, the Milky Way and the Andromeda Galaxy, came together when smaller objects collided and merged. Astronomers of today can see satellite or 'dwarf galaxies' orbiting both the Milky Way and the Andromeda Galaxy. The Milky Way's largest satellites are called the large and Small Magellanic Clouds. They appear to be orbiting our home galaxy "in a billions-of-years-long orbit and may never actually merge with the Milky Way." That said, they are affected by the Milky Way's gravitational pull and may only be approaching our galaxy for the first time.
Large-galaxy collisions to occur. And when that happens, huge new super-sized galaxies are formed. When these two large galaxies merge, they lose their spiral structure due to gravitational pull. This newly-created mass will then be an elliptical galaxy. What I found interesting is that while galaxies may merge, the merger process doesn't always hurt the stars they contain. Why is that? Astronomers believe that while galaxies do contain loads of stars and planets, they also have lots of empty space. When these intergalactic mergers happen, the stars and planets are pushed out into the open places and, thus, are not necessarily hurt or injured. Colliding galaxies often contain giant clouds of dust and gas. When galaxies that do not contain large amounts of gas collide, they enter a period of rapid star formation. "Such a merges system is known as a starburst galaxy."
A close-to-home example of a galaxy merger is one that will happen between the Milky Way and the Andromeda Galaxy. The result, which will take millions of years to happen, will create a new galaxy. just in case you were wondering, the Andromeda Galaxy is 2.5 million light years away from us so the collision won't be happening anytime soon. No need to contact your insurance company just yet!
What will happen to Planet Earth when these two galaxies finally do collide? Scientists say that probably very little will happen to our solar system. "Since most of Andromeda is empty space, gas, and dust, much like the Milky Way, many of the stars should find new orbits around the combined galactic center. That center may have as many as three supermassive black holes until they, too, merge." The greater danger to our solar system will be the increasing brightness of our Sun. The sun will eventually use up its hydrogen fuel and will then evolve into a "red giant." That should happen, say the scientists, in about four billion years. Life most likely will have died out long before any of these events take place. It could also be that our very future descendants "will have figured out a way to escape the solar system and find a world with a younger star." Okay, all you wanna-be astronomers...now's the time to begin figuring out an escape strategy! It's never too soon to plan ahead....
I hope you've enjoyed my little science lesson today. I'm so excited by what I learned that I think I'll pick up little Quigley when he gets out of school this afternoon and we'll head over the Lily Pad Planetarium for an afternoon of star-gazing.
I invite you back here again tomorrow when my wise teacher, The Dharma Frog, will once again be here bright and early for my weekly life lesson. Until then,