As a part of the universe, there are many galaxies in the universe contains nebula, planets, stars, etc. the Milkyway is also a galaxy in which we are. Our known stars all are in this galaxy. In fact, about all space elements, we have explored are in this galaxy Milky way. But, what is at the center of the milky way galaxy is a very important question scientists are curious to know.
However today askerweb.com is not telling about Milkyway.
Today we are discussing what is at the center of the milky way galaxy?
not only our milky way but also every galaxy contents a black hole at the center. It is Sagittarius A*, a black hole situated at the center of the Milkyway.
But how was Sagittarius A* discovered? Today we will know it in 7 steps:
Optical telescope in 1920:
In 1920 we were able to discover all galaxies including our Milkyway. But then we could not explore the center of any galaxy. The reason is that the black hole cannot be observed by an optical telescope, because wire optical telescope we only can watch the things which reflected irradiated visible light only. Because we can see only things for their visible light. Now a black hole is such a thing that does not reflect or radiate any light also cannot avoid the black hole. Blackhole absorbs light.
To solve the problem of optical telescope radio telescope comes which deals with em radiation this telescope captures the radiations and analyzing its frequencies and wavelengths to determine various elements as well as black holes.
Note: visible light is one type of EM radiation but it is of such frequency (10^14 Hz) that human is able to feel it.
In 1930 Jansky’s antenna:
The father of radio astronomy, Karl G. Jansky designed a radio antenna of 100 feet in diameter and 20 feet in height he was worked in “Bell telephone laboratory”. 20.5 megahertz radio waves can be captured by his antenna it was situated in a turning table for capturing various OFC analyzed and there are divided into three types.
1. signal from a near thunderstorm.
2. Signals from the far thunderstorm.
3. Unknown noise (Hiss).
The star noise
First, it was thought that the third type of noise was coming from the sun, but soon it was proved wrong and the astronomers came to know that the unknown noise was from the center of the Milkyway. Jansky named it the star noise but as Jansky has not any relation with astronomy and cosmology nobody listened to him.
Source of the star noise: Sagittarius A*
The more astrophysics developed the more we learn about the centre of Milky way we came to know about the existence of a black hole at the centre of the Milkyway we named it Sagittarius A* (situated in the Sagittarius constellation).
But now what the question comes is-
Is Sagittarius A* a black hole?
an array of many radio observatory is that works like a giant radio telescope we can measure very small change accurately the event horizon telescope it’s such an example by which we discover the black hole at the center of the M87 on 10th April 2019.
From 1970 barrack Bellic and Robert brown watched Sagittarius by NRAO (National radio astronomy observatory) baseline interferometer and on 13th February 1974, they explore very complex and bright elements and guessed a black hole situated at Sagittarius.
But, on 16th October 2002, an international team led by German astrophysics Reinhard Genzel watched a star S2 moving around something near the Sagittarius star cluster. After a close look, it was watched that there were other stars too moving in such a way. later it was also seen that the central object around which the stars were moving was very very massive in terms of mass and size. These all with other important property can easily prove that Sagittarius A* was nothing but a black hole. This proof immediately also proved that every galaxy in this universe has at least one black hole situated at its center. Now if anybody asks you “is there a black hole at the center of every galaxy?“, the answer is definitely yes.
What is S5-HVS1?
like S2 there was another Star S5-HVS1 which was two times larger and 10 times brighter than our sun. It was in the grease constellation in the southern sky Its name S5 suggests 5 “S”(Southern Stellar Stream Spectroscopic Survey) & “HV” suggests “Hyper Velocity”. This star was discovered by Sergey Koposov, assistant professor of Physics at Carnegie Mellon University.
But, why I’m telling you about only this star? That’s because this star dramatically is going away from the black hole leaving its strong gravitational force. But why & how?
Why is S5-HVS1 leaving Sagittarius A* black hole?
It’s a very strange fact of leaving a black hole avoiding its strong gravitational force, where a black hole’s gravitational force is so strong that even light can’t escape it. However, there are several theories. According to one theory, some astronomers say that whether a black hole attracts a star or repulses a star, depends on its other stars. If two similar stars attract one another & if they are suddenly attracted by a black hole, the black hole can attract and absorb one star & with the same force have to repulse another star. That may be the reason for the strange behavior of star S5-HVS1. Mind it, I said “maybe”, because it’s still a theory.