Every now and then, we hear extraordinary stories about cosmos, stars and mysterious objects. One recent example includes unusual radio bursts, which piqued the interest of the scientific community because they had no idea what was going onn. Currently, a rogue stellar body, perhaps a failed star, is moving towards the center of the Milky Way galaxy at a speed of 1.2 million mph.
CWISE J1249+3621. Located about 400 light-years away from Earth, CWISE J1249+3621 is the protagonist of this story. This object has a mass that’s about 8% that of the Sun, making it about 80 times the mass of Jupiter. Scientists consider it to be on the boundary between a star and a group of objects called “brown dwarfs,” often referred to as "failed stars."
Citizen scientists involved in the Backyard Worlds: Planet 9 project first spotted CWISE J1249+3621. The project uses data from NASA’s Wide-field Infrared Survey Explorer (WISE) to identify faint, moving objects relatively close to the Sun. Astronomers later confirmed the existence of the object using the Keck telescope and were surprised by its speed.
“Outside” the Milky Way. Adam Burgasser, the leader of the study team from the University of California, told Space.com that the star or brown dwarf is moving with extreme velocity, fast enough to not be bound to the Milky Way. “It joins a collection of ‘hypervelocity’ stars that have been found over the past few decades, most of which are thousands of light-years from the Sun, whereas this source is a ‘mere’ 400 light-years away,” he said.
An Iillustration of a brown dwarf with an aurora, compared to the sizes of some other astronomical objects.
Composition. The researchers found a peculiar chemical composition in the atmosphere of the fast-moving object. They plan to use this information to determine its possible origins. “This discovery mainly opens up a new pathway to studying brown dwarfs that are in remote regions of the Milky Way, including its center, its halo and its various globular clusters and satellites,” Burgasser said.
The mystery surrounding its velocity. Interestingly enough, CWISE J1249+3621 is a celestial object with a mass that places it between a brown dwarf and a star. It’s currently the lowest mass, high-velocity “star” known to astronomers. As Burgasser mentions, it’s equally important to note that this “discovery indicates that whatever process (or processes) causes these stars to run away must operate at both high and low masses.”
First possible explanation: ejection. What made CWISE J1240-3621 travel at such speed? Although there’s no definitive answer, astronomers currently believe the supermassive black hole Sagittarius A* could’ve ejected it from the center of the Milky Way. This process is commonly used to explain the origins of other hypervelocity stars.
Second possibility: cosmic vampire. “Notably, our star is moving into the center, not away, but it might be on a return trip after being ejected previously,” Burgasser said. Alternatively, it might be running away from a “cosmic vampire,” suggesting that it may have been part of a binary system with a white dwarf stellar corpse that was tearing material away from it. This process causes the white dwarf to explode, propelling the stellar body to speed off.
Third possibility: black holes. Another possibility astronomers are considering involves ejection from a globular cluster through dynamic interactions with black holes in the center of the cluster. “Recent simulations show that this should happen several times over the age of the Milky Way,” Burgasser told Space.
Last possibility: X. I marked this option with an X because it’s the possibility that doesn’t rule out the unknown. The researchers can’t ignore the possibility that the potential brown dwarf is an intruder in our galaxy that came from outside the Milky Way.
However, in their study, they note that the fact that it’s passing through the plane of our Milky Way makes that a less likely case. According to the researchers, “The orbit is certainly the most surprising aspect of this object; it is moving radially in and out of the center of the Milky Way and almost perfectly in the plane. Most of the high-velocity stars we see are on much more chaotic or inclined orbits. I think this is a real clue to its real origin.”
This article was written by Miguel Jorge and originally published in Spanish on Xataka.
Image | NASA
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