A gargantuan gas cloud, made of mostly hydrogen, is racing toward the Milky Way at a whopping speed, and it will probably smash into our galaxy in about 30 million years, scientists say.
The gas cloud was first spotted in the 1960s. According to scientists, it is moving towards us at about 700,000 miles per hour (1.12 million km/h) – that would be the equivalent of approximately 194 miles per second.
Andrew Fox, lead researcher of the study and an astronomer at the Space Telescope Science Institute (STScI) in Baltimore, Maryland, said that the gas cloud was actually ejected from the Milky Way galaxy a long time ago and it is now coming home.
The Smith Cloud – named after Gail Smith, the doctoral astronomy student who first discovered it – is one-of-a-kind among the other gas clouds found outside our galaxy, because its trajectory is known.
Dr. Fox said that studying the Smith Cloud may help better understand the accumulation of gas onto galaxies – which is currently a subject of high interest in astronomy.
Astronomers estimate that the Smith Cloud will reach the Milky Way in about 30 million years. The collision will generate a spectacular explosion of star formation; up to two million new suns could be produced.
If the Smith Cloud were visible to the naked eye, we would see it in the sky and it would have an apparent diameter thirty times bigger than that of the full moon, according to astronomers.
The team using the Hubble Space Telescope looked at the light’s pathway that originated in three galaxies located billions of years beyond the Smith Cloud, which helped them figure out the composition of the cloud.
They found that the chemical composition of the Smith Cloud matched that of the outer disk of the Milky Way. In that region, the interstellar gas is not as rich in heavy metals as it is near the Sun, according to Dr. Fox.
Based on its composition – specifically the sulphur levels – scientists were able to determine that the cloud originated neither outside the galaxy (because it was not of pristine hydrogen), nor from a failed galaxy, but rather from our own galaxy, the Milky Way.
Dr. Nicolas Lehner, lead researcher on the project and a Research Associate Professor at the University of Notre Dame in Indiana, said that the gas cloud may have been pushed out from the galaxy by the death of many massive stars.
Image Source: nasa