What size for supermassive black holes?

I read that our supermassive black hole, Sagittarius A *, had a diameter similar to the rotation of the planet Mercury around the Sun. While M87 * has a diameter that exceeds the rotation of the dwarf planet Pluto. My question is: within supermassive black holes, is there a classification of their size? This is the question Gerard Contents for writing Science and the Future on our Facebook page. This is our Question of the Week, and here is our answer. Thank you all for your participation and loyalty.

Different classes of black holes

The publication on 12 May 2022 of the image of the central black hole in our galaxy, the Milky Way, apparently aroused enormous public interest in these mysterious objects. Before focusing on supermassive black holes like Sagittarius A *, it is probably wise to return to the different classes of black holes that astronomers know. The most common are the black holes of the stars, which have a mass of a few suns and a diameter of a few kilometers. They occur as a result of gravitational collapse of massive star nuclei at the end of their lives, which explode in the form of a supernova. Much harder to spot, black holes with intermediate mass have masses between 100 and one million solar masses. These are objects believed to be back from the explosion of giant stars that ignited in the young universe. To tell the truth, there is no formal evidence to validate their existence, but in early 2022, an international team published results that strongly suggested that one could hide in the heart of B023-G078, the stripped core of a small galaxy.

Size comparison of the two black holes depicted by the Event Horizon Telescope (EHT) collaboration: M87 *, in the heart of the Messier 87 galaxy, and Sagittarius A * (Sgr A *), in the center of the Milky Way. The picture shows the scale for Sgr A * in relation to M87 * and other solar system elements such as Pluto and Mercury’s orbits. Credit: EHT collaboration (caption: Lia Medeiros, xkcd).

Black holes and records

Finally, this is the topic that interests us today, the supermassive black holes that host the centers of the largest galaxies in the universe are now well known. Their origin is still not explained, and the mechanisms of the formation of such cosmic monsters are still very mysterious. And the term monsters is not robbed: some can reach billions of solar masses! In addition, astrophysicists prefer to catalog the criterion mass rather than size, although these data are also measured. And to clarify Gérard Content’s question, the size of Sagittarius A * is actually close to Mercury’s orbit around the Sun, and its mass is equivalent to 4 million times that of our star. But the M87 * with its 6.5 billion solar masses does not once measure Pluto’s orbit, but more than three times that! It’s about 38 billion kilometers … The image above illustrates this difference well.

There really is not a scale that is calibrated to the mass or size of supermassive black holes to classify them. However, specialists have established a link between the mass of black holes and the flicker coming from their growth disk. Their research could lead to a new method of characterizing these objects. Finally, note that the largest known black hole is TON 618, a quasar located 10.4 billion light-years from Earth, with its 66 billion solar masses and a size about 100 times the distance of the Sun-Pluto. ! The smallest supermassive black hole is almost smaller than an intermediate black hole: almost 200,000 solar masses … It is located in a dwarf galaxy Mrk 462, which contains a few hundred million stars. It would be in full growth and its existence could explain how the largest black holes can form. Its discovery was announced on January 10, 2022, there is still much to learn from the latter …

Leave a Comment