What do we know about Sagittarius A*, the supermassive black hole at the center of the Milky Way?

Black holes are bodies so massive that they have a gravitational force capable of swallowing everything around them, including light. Although these objects were predicted with Albert Einstein’s theory of general relativity at the beginning of the last century, astronomers were only able to confirm their existence when they began to detect several unexplained radio emissions that coincided with the German physicist’s hypothesis.

One of these energy sources inhabits the center of the Milky Way. It is a supermassive black hole called Sagittarius A* (or Sgr A*) because it is located, from Earth’s perspective, within the Sagittarius constellation.

We tell you everything that is known about this enigmatic dark body.

There are different types of black holes depending on their mass; that is, the amount of matter it possesses. The stellar they have from five to tens of times the mass of the Sun; the intermediates between hundreds and thousands; and the supermassive between millions and billions.

The latter are located in the center of all known galaxies. In ours is Sagittarius A*, possessor of four million solar masses.

Sagittarius A* has a diameter of 44 million kilometers, as measured by its event horizon, the black, spherical surface that marks the boundary where matter and energy can no longer escape gravity.

On a closer scale, we could say that its size is 120 times the distance between the Earth and the Moon or a little less than the distance that separates Mercury from the Sun (approximately 58 million kilometers).

The black hole at the heart of our galaxy is 27,000 light-years away from Earth. In other words, it is just under a third of the total diameter of the Milky Way, which measures 106,000 light-years.

The existence of a black hole can be inferred by observing the alteration of nearby stars that are attracted by the strong gravitational pull. Some of them disappear, are violently expelled or the light they emit is distorted to longer wavelengths (infrared).

In the mid-1990s, astronomers Reinhard Genzel Y Andrea M. Ghez — winners of the Nobel Prize in Physics in 2020 for this finding — replicated this technique to find Sagittarius A*, but first they had to overcome a couple of obstacles. First, to have telescopes that can see in infrared wavelengths —and that go through obstacles such as stellar clouds—; and second, to find the stars closest to the black hole to find out its real size.

For more than two decades, the team of astronomers detected several stars close to Sgr A* with telescopes from the European Southern Observatory (ESO). one of this era S29 which, at its closest point to the event horizon, was beginning to travel at an impressive speed of 8,740 km/s. despite being 13,000 million kilometers away, 90 times the distance between the Sun and the Earth.

These observations strengthened the existence of a supermassive black hole in the Milky Way and at the same time made it possible to determine its characteristics. Despite these advances, there is still no image of the massive object.

Capturing images of the silhouette of a black hole is already possible with the Event Horizon Telescope (EHT), an international project of eight radio telescopes that together form a virtual lens the size of the Earth.

The first great feat of EHT was to photograph the black hole of the galaxy Messier 87 (M87): a colossus of 6.5 billion solar masses located 55 million light years away.

Since then, EHT scientists have tried to capture the portrait of Sagittarius A*, a task that has not been easy despite being in our cosmic neighborhood. This is due to all the stardust that gets between the Earth and the galactic center.

Source-larepublica.pe