Runaway Star Exits the Milky Way Galaxy Named S5-HVS1!!

A star has been spotted by astronomers, which is moving out from the Milky Way galaxy at an astonishing speed of 1,700 km/second. This has happened subsequent to an encounter with a massive black hole located at the center of our galaxy. 

Named as S5-HVS1, the star is moving at breakneck speed never recorded by astronomers before. At the speed with which it is moving, it will soon exit the premises of the Milky Way in about 100m years. After that, it will continue its journey in outer space for the remainder of its years. 

Interestingly enough, it was predicted 3 decades earlier that black holes have the ability to throw stars out from the galaxy at stellar speeds (no pun intended), but this is the first time the phenomena have been recorded live. 

What are Hypervelocity Stars

Let’s back up a little bit. By definition, the hypervelocity stars are fast-paced, which move at twice the speed of normal stars, 1 million mph to be exact. These stars were first discovered by the astronomers in 2005 and approximately 30 of these stars have been discovered as of yet. 

There is no stopping this star and its present trajectory indicates that it will head out in intergalactic space and continue moving. The S5-HVS1 is presently located in the Grus constellation, approximately 29,000 light-years away. Its velocity is extremely high and it is highly unlikely that the star will ever return to the Milky Way. 

It was previously believed that to eject a star from the galaxy, the energy would be drawn from the center of the galaxy. At the Milky Way’s center, a massive black hole is present with a mass 4 times larger than that of our sun. It can act as a gravitational slingshot for the star. 

How did it happen?

According to the astronomers tracking the tear away star, it was a part of the binary star system in the Milky Way about 5m years ago. For those who do not know, a binary star system consists of two stars, which revolves around their barycenter. This star system neared a bit close to Sagittarius A*, the renowned black hole at the center of the Milky Way. It is interesting to note that when this actually happened, the humans were still learning to walk in an upright position. 

The star was traced to the center of the galaxy, something that was not expected. The astronomers were actually searching for the remains of smaller galaxies, which revolve around the Milky Way. Their telescope can measure at least 400 objects at any given time. In its place, they discovered a star traversing the galaxy’s outskirts. If a black hole comes in close contact with a binary star system, the outcome is undesirable for the said star system. If the binary star system whizzes past the black hole, it is captured by a black hole and ejected at breakneck speeds. This is exactly what happened in this case, too. 

The S5-HVS1 is categorized as an A-type star, a relatively younger star when compared to our sun that is 4.6 billion years old. More interestingly, the surface temperature of an A-type star lies in the range of 13,000 Fahrenheit to 18,000 Fahrenheit. On the other hand, the surface temperature of our star (a yellow dwarf star) is 9,940 Fahrenheit. 

Hills Mechanism in Action

Jack Hills proposed 3 decades ago that superfast stars could be, in theory, ejected by black holes. The phenomena came to be known as Hills mechanism. 

When the twin stars moved inwards, at one point the S5-HVS1 switched into this binary partnership with the black hole, which resulted in the renowned Hills Mechanism. This dynamic allowed the star to be ejected at an extremely high speed never seen before. The astronomers used the distance and speed from Earth to ascertain the star’s ejection from Sagittarius A*. 

As the gravitational tussle ensued, the companion star was eventually captured by this black hole and released at a shockingly high speed. According to astronomers, this was the first recorded demonstration of Hills Mechanism. The binary star system formed a part of our galactic center, an environment very different from the one on earth. 

The speed of the star is 10 times faster than most of the stars present in the Milky Way galaxy, including our own sun. As of yet, it is the third-fastest star to be recorded in human history. The previous two were those whose speeds had been boosted due to supernova explosions. With the exception of these special cases, this star is by far the fastest to date. 

The Southern Stellar Stream Spectroscopic Survey (S5) was behind this discovery. The primary goal of S5 is to keep an eye on the stellar streams. Some spare resources are dedicated to look over interesting objects present in the galaxy.

The S5 is constantly on the lookout for such interesting phenomena and we will be too waiting in our astronaut costumes !