The Milky Way black hole ejected a star into intergalactic space at 6 million km/h

The Milky Way black hole ejected a star into intergalactic space at 6 million km/h

What we are seeing here is “a visitor from a strange land…”

During a time when humanity's ancestors were learning to walk upright, use their hands, and create the first primitive tools, cosmic events left a mark on our galaxy that our developed society would later see, millions of years later.

Astronomers have traced the trajectory of the so-called hypervelocity star through time, concluding that it was ejected from the monstrous black hole at the center of our galaxy during a time when civilization as we know it did not exist.

Dubbed S5-HVS1, this cosmic body is an “A-type main sequence star” and is considered the fastest ever discovered by astronomers.

Measurements of its trajectory have revealed that the cosmic body is traveling at almost 1,755 km/s, or about four million miles per hour.

The black hole at the center of our galaxy, Sagittarius A*, has been visualized in virtual reality for the first time. Image credit: J.Davelaar 2018

This took place, according to astronomers' calculations, about 5 million years ago. The dramatic ejection marked the confirmation of the so-called Hills mechanism.

The Hill mechanism occurs when a supermassive black hole disrupts a binary star.

Our Milky Way, for example, is home to Sagittarius A*, a supermassive black hole that is about 4 million times the mass of the Sun. The Hills mechanism describes how stars separate and then leave each other to continue their journey separately.

What astronomers measured in 2019 was precisely that; a star launched into orbit around a black hole while its companion star was launched into intergalactic space at incredibly high speed.

To understand the origin of S5-HVS1, astronomers studied the kinematics and traced the orbit back in time. Incredibly, they discovered that the star dates back to the Galactic Center of the Milky Way, where it was ejected at a speed of 1800 km/s between 5 and 4.8 million years ago, making S5-HVS the first clear demonstration of the Hill Mechanism. and one of the fastest stars in the galaxy.

The star was observed on its journey approaching Earth at a distance of around 29,000 light years, traveling more than ten times faster than any other star in the Milky Way.

Such is its speed that astronomers say that one day it will inevitably leave the Milky Way and never return.

The discovery was of great importance but also surprising. Astronomers have theorized for years that black holes could eject stars at unimaginable speeds. Still, they have never associated a fast-moving star with the black hole at the center of the galaxy.

Observing and measuring the trajectory of S5-HVS1 is of great importance for astronomers since it must have formed in the galactic center. Furthermore, it is unique; The environment at the center of the Milky Way is completely alien compared to our local galactic environment. This makes S5-HVS1 “a visitor from a strange land.”