A massive gas cloud flung out of the Milky Way is coming back – hurtling back at an astoundingly-fast speed.

Known as Smith Cloud, the giant boomeranged gas collection was discovered in the 1960s and is expected to collide with the galaxy in around 30 million years.

New research delving on its composition showed that it contains elements similar to the sun, and that it hailed from the outer edges of the Milky Way and not intergalactic space like previously thought.

NASA reported that the starless sensation travels at almost 700,000 mph, and would have a size of around 30 times the moon’s diameter if it were visible.

Researchers tried to gauge the Smith Cloud composition by using NASA’s Hubble Space Telescope. The cloud absorbs light in certain wavelengths from background galaxies passing through it, and drops in brightness show which elements can be identified within it.

Scientists specifically focused on finding sulfur, a reliable indicator of the number of elements that are heavier than helium and hydrogen in the gas cloud.

“By measuring sulfur, you can learn how enriched in sulfur atoms the cloud is compared to the Sun,” says team leader Andrew Fox from the Space Telescope Science Institute in Baltimore.

The findings: the Smith Cloud appears as abundant in sulfur as the outer disk of the Milky Way, a site around 40,000 light years away from galactic center and around 15,000 light years more distant than our solar system and sun. This meant the object was tainted by material coming from stars.

The cloud would contain only helium and hydrogen if it came from intergalactic space. However, this wasn’t the case – instead, it appeared to have been quite acquainted with the Milky Way and was only ejected from its outer disk, now managing to boomerang its way back.

The team also said that the Smith Cloud contains plenty of gas to produce two million suns once it hits the disk. While they have detected a number of huge clouds of gas in our galaxy that may fuel future star formation, this particular cloud has far more familiar origins.

Study author and astrophysicist Nicolas Lehner added that the Smith Cloud proves to be among the best illustrations of the importance of recycled gas in galaxies’ evolution.

The findings were discussed in the Astrophysical Journal Letters.