A giant hydrogen gas cloud is heading towards our Milky Way where it would almost certainly meet its demise, but researchers believe the object could contain a life-saving magnetic field.
If the object, called the Smith Cloud, does survive the plunge it could explain how high velocity clouds (HVCs) remain intact, but that won't be for about 30 million years, a National Radio Astronomy Observatory news release reported.
"The million-degree upper atmosphere of the Galaxy ought to destroy these hydrogen clouds before they ever reach the disk, where most stars are formed," Alex Hill, an astronomer at Australia's Commonwealth Scientific and Industrial Research Organization (CSIRO) and lead author of the paper, reported. "New observations reveal one of these clouds in the process of being shredded, but a protective magnetic field shields the cloud and may help it survive its plunge."
HVCs are fairly common in the universe, but very few sync up with the rotation of our own galaxy. The researchers believe these objects are "left-over building blocks of galaxy formation" or remnants of millions-of-years-old galactic close encounters.
The researchers are not sure how the Smith Cloud was formed.
"The field we observe now is too large to have existed in its current state when the cloud was formed," said Hill. "The field was probably magnified by the cloud's motion through the halo."
Computer simulations show the gas should not be able to survive a descent into another galaxy.
"We have long had trouble understanding how HVCs reach the Galactic disk," Hill said. "There's good reason to believe that magnetic fields can prevent their 'burning up' in the halo like a meteorite burning up in Earth's atmosphere."
Past research shows the cloud may have plunged through the Milky Way once before.
"The Smith Cloud is unique among high-velocity clouds because it is so clearly interacting with and merging with the Milky Way," Felix J. Lockman, an astronomer at the National Radio Astronomy Observatory (NRAO), said. "Its comet-like appearance indicates it's already feeling the Milky Way's influence."
The team believes when the cloud breaks the Milky Way's barrier it could result in a "spectacular burst of star formation" appearing in a ring. If one could see the cloud with the naked eye, it would appear to cover as much of the sky as the constellation Orion.
"Our Galaxy is in an incredibly dynamic environment," Hill said, "and how it interacts with that environment determines whether stars like the Sun will continue to form."
