In the heart of Milky Way, hundreds of stars closely orbit a supermassive black hole. The stars posses big enough orbits, and their motion is described by Kepler’s laws of motion and Newtonian gravity.
But, astronomers found that only a few stars orbit so closely that Einstein’s theory of general relativity can precisely describe their orbits. The star with the smallest orbit, for instance, is dubbed S62. Its closest approach to the black hole has it running more than 8 % of light speed. Such results are quite intriguing. Here is what you need to know.
The Fastest Star Ever Seen is Now Investigated
Milky Way’s supermassive black hole is dubbed Sagittarius A* (SgrA*). It represents a mass of almost 4 million suns, a volume defined by the stars that orbit it. For years, astronomers have followed the movement of these stars. By measuring their orbits, they can determine the mass of SgrA*.
Astronomers’ observations have recently become so accurate that they can calculate now more than the black hole’s mass. They can examine whether their understanding of black holes is real.
The most analyzed star orbiting SgrA* is S2. It is a bright, blue massive star that orbits the black hole every 16 years. For instance, in 2018, S2 realized its first approach to the black hole, offering astronomers a chance to track an effect of relativity dubbed the gravitational redshift.
It’s like you’re tossing a ball up into the air. It’ll slow down as it rises. Also, if you shine a beam of light into the sky, the light doesn’t seem to slow down, but gravity will take away some of its energy. A beam of light becomes then redshifted as it crawls out of a gravitational well.
The effect has been recognized in the lab, but S2 offered astronomers a chance to witness it in the real world. At the close approach, the light of S2 turned red as anticipated.
S2 was believed to be the closest star to SgrA*, but astronomers discovered S62, a star almost twice as massive as the sun that orbits the black hole every 10 years. S62’s speed approaches 8 % of the velocity of light, which is so fast that time dilation kicks in. An hour at S62 would be approximately 100 Earth minutes.
In the fall of 2022, S62 will realize another close approach to SgrA*. Astronomers will examine the effects of relativity even more accurately than the close approach of S2.
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