Our home galaxy, the Milky Way, is a giant, encompassing every individual star the unaided eye can see. But the Milky Way hasn’t always been so huge. Instead, it grew over time, as smaller galaxies smashed together, squeezing their gas clouds and triggering the birth of new stars.
Astronomers have recently seen this process in action near the edge of the galaxy’s disk.
The Milky Way is so large that many lesser galaxies go around it the way moons orbit a planet. The two brightest of these satellite galaxies are the Magellanic Clouds. They’re named for Portuguese explorer Ferdinand Magellan, who described them as clouds in the southern sky.
The clouds abound with gas, which is the raw material for making new stars. The two galaxies are shedding a stream of gas that wraps around much of the Milky Way. Try though they might, though, astronomers couldn’t find any stars in this ribbon of gas until recently.
A study examined the stream and detected six bright, young stars within it. The stars likely were born as the gas from the Magellanic Clouds collided with gas at the edge of the Milky Way. That squeezed the gas from the Magellanic clouds, causing it to collapse and give birth to new stars. The newborn stars add even more luster to the Milky Way. And they illustrate how our home galaxy has grown into a giant that’s home to hundreds of billions of stars.
We’ll talk about a collision right here in the solar system tomorrow.
Script by Ken Croswell, Copyright 2014
For more skywatching tips, astronomy news, and much more, read StarDate magazine.