Astronomers have spotted a massive gas cloud making its way toward the Milky Way Galaxy after it was ejected tens of millions of years ago.

According to Discovery News, the "Smith Cloud" was first identified in 1963 when the Gail P. Smith spotted it with the Dwingeloo Radio Observatory in the Netherlands. Its dimensions are about 11,000 light years by 2,500 light years, and it is traveling at an approximate speed of 700,000 mph.

A team of astronomers published a study on the Smith Cloud in the Astrophysical Journal.

"The cloud is an example of how the galaxy is changing with time," study lead author Andrew Fox, of the Space Telescope Science Institute in Baltimore, Md., said in a press release. "It's telling us that the Milky Way is a bubbling, very active place where gas can be thrown out of one part of the disk and then return back down into another.

The researchers confirmed their measurements of the Smith Cloud by looking for sulfur and noting how ultraviolet light filtered through it.

"Our galaxy is recycling its gas through clouds, the Smith Cloud being one example, and will form stars in different places than before. Hubble's measurements of the Smith Cloud are helping us to visualize how active the disks of galaxies are," Fox said. "By measuring sulfur, you can learn how enriched in sulfur atoms the cloud is compared to the sun."