Every now and then the Milky Way throws a star. The displaced star is typically ejected from the chaotic area in the center of the galaxy where our Supermassives Black Hole (SMBH) lives. However, at least one of them has been ejected from the relatively quiet galactic disk, a discovery in which astronomers are completely re-thinking this phenomenon of star ejection.
"This discovery drastically changes our view of the origin of fast-moving stars."
Monica Valluri, research professor, Department of Astronomy, U-M College of Literature, Science and the Arts.
The star in question is a fast-moving star, or what is also known as a hyper-speed star. Overspeed stars are rare in our galaxy. The first was discovered in 2005, and so far researchers have discovered less than 30 of them. They travel at more than 1
To understand what's going on, take a look at the Milky Way's overall structure.
The galactic vault is in the middle, and deep in the heart of this vault is the SMBH rifleman of our galaxy, Sagittarius A * (Sag. A-Star). Around him, the galactic disk of the galaxy's spiral arms spreads. Of less importance in this study are the stellar halo and globular clusters.
When a star is kicked out of the galaxy, it is usually a star of a binary pair. Scientists believe that when a binary pair gets too close to the SMBH and its overwhelming gravity, the hole captures one of the stars. The other star is shot into space in a "gravitational spinner". The black hole must be a supermassive, because only they have enough power to accelerate these runaway stars to such high speeds.
But researchers from the University of Michigan have identified a hypersensitive star that appears to have been ejected from the star disc rather than the galactic bulge.
Monica Valluri and Kohei Hattori traced a star named Hypervelocity
LAMOST-HVS1, a hyper-speed star closer to the Sun. They used one of the Magellan telescopes to measure the speed and position of the star. Then they teamed up with other colleagues and combined their data with data from ESA's Gaia mission to trace the trajectory of Hypervelocity back to its origin. They were surprised when the star's origin was not the vault, but the galactic disk.
"This discovery dramatically changes our view of the emergence of fast-moving stars," said Monica Valluri, a professor at the Department of Astronomy at U-M's College of Literature, Science and the Arts. "The fact that the trajectory of this massive, fast-moving star lies in the disk is due to the fact that in the Galactic Center, the most extreme environments required to eject fast-moving stars are at locations other than supermassive black holes can arise. "  "We must consider other possibilities for the genesis of the star."
Kohei Hattori, Postdoctoral, University of Michigan.
"We thought this star came from the galactic center. But if you look at the trajectory it is clear that this is not related to the galactic center, "Hattori said. "We must consider other possibilities for the formation of the star."
What would these possibilities be?
The authors are not sure at this point. One possibility is an encounter of a different kind. The out-of-control star may have had an encounter with a host of other massive stars and has been ejected through a complex interaction of gravity.
This type of encounter has led to out-of-control stars in the past. But nothing works as fast as the LAMOST-HVS1. Star Cluster outliers were clocked at 40-100 km / s (25-62 miles / second), but none of them approached the 500 km / second that stars are on the way.
Another, more exotic possibility It's a black hole. There may be more black gravity holes in the galactic disk to launch the star into space. But that's not much more than a guess.
If it's a star cluster launching LAMOST-HVS1, it's one nobody has ever seen. The hyper-pointed star came from the Norma spiral galaxy, an area that is not associated with any known massive star cluster. However, this area is well covered by dust. There could be a cluster with enough mass to eject the star.
If astronomers could find a massive pile there, it could show that all the stars were ejected at high speed from encounters with massive clusters and the SMBH has nothing to do with it. Or take note here, the massive star cluster could have a middle black hole in the middle strong enough to eject the star.
However, the origin of LAMOST-HVS1 remains uncertain at first.