Hubble may have discovered the closest known intermediate-mass black hole

We remember that the Swedish Academy awarded the Nobel Prize in Physics in 2020 to Andrea Gess and Reinhard Jensel. For the discovery of a very small compact object at the center of our galaxy “. The correct formulation is important because while most astrophysicists think this object is indeed a supermassive black hole, this has not been disproved by the observations of the collaboration. Event Horizon Telescope, we don’t have a definitive proof yet, but are pretty close. More generally, it is reasonable to think that this evidence will come from the study of gravitational waves.

The two researchers and their teams of collaborators discovered the tiny object after more than a decade of studying the motions of stars near the center of the Milky Way orbiting a mysterious radio wave named Sgr A*. Therefore, this source is associated with a small mass distribution in a block that, according to the equations of general relativity, turns into a black hole with more than 4 million solar masses. In fact, this material does not radiate itself and the electromagnetic waves we detect come from the material surrounding this small star.

This simulation shows the orbits of a small group of stars located near the supermassive black hole at the center of the Milky Way. In 2018, one of these stars, called S2, passed very close to the black hole and was the subject of an intensive campaign of observations using the ESO telescopes. Its behavior was consistent with the predictions of Einstein’s theory of general relativity – though not with Newton’s theory of gravity. © ESO, L. Calçada,

A Universal Law for the Size of Black Holes?

In fact, it has been believed since the late 1960s, and observations have strengthened this thesis, that at the heart of all large galaxies are supermassive black holes of at least one million solar masses. We also note that the mass of detected black holes is largely proportional to the mass of the host galaxy.

We also know that the Milky Way contains many black holes of about ten solar masses each. Some researchers have wondered if the law of proportionality found in large galaxies does not hold for dwarf galaxies and globular clusters.

If so, there should be intermediate mass black holes between about a hundred solar masses and a million solar masses. As we track these objects, some candidates are visible outside our galaxy, such as 3XMM J215022.4−055108, discovered by the Hubble telescope in 2020, and HLX-1, identified in 2009. Galaxies. Each of these potential black holes has the mass of tens of thousands of Suns, and some observed clusters may be the nuclei of now-extinct dwarf galaxies that have been displaced by the galaxies’ tidal forces. .

Today, an article was published Monthly Notices of the Royal Astronomical Society by a team of researchers led by astronomer Eduardo Vitral Space Telescope Science Institute From Baltimore, Maryland in the United States, it is still the Hubble telescope, which indicates that interstellar black holes do exist. After all, for the first time, these observations concern the Milky Way, as they relate to the motions of stars in Messier 4 (M4), a globular cluster about 7,000 light-years away from the Solar System.

The video begins with a panoramic view of the Milky Way’s spectacular central regions. We are approaching Scorpio. Close to its nearest star, Antares, is the globular cluster Messier 4, one of the closest star systems to Earth. Detailed images of the cluster at the end of this video from the WFI camera on the MPG/ESO 2.2-meter telescope at ESO’s La Silla Observatory in Chile, along with a close-up of the area that terminates the power plant. NASA/ESA Hubble Space Telescope. © ESO-ESA-Nasa, Digitized Sky Survey 2, Nick Risinger (

The closest globular cluster to the Sun

Still known as NGC 6121 and located in the constellation Scorpius, M4 is actually the closest globular cluster to the Sun. It was discovered in 1746 by the Swiss astronomer Jean-Philippe Lois de Cheseaux. Eduardo Vitral and his collaborators now suggest a small body of 800 solar masses. Again, given the motion of the stars around it, it must be a black hole and in this case an intermediate-mass black hole.

After more than 12 years of observations, astrophysicists have come to this conclusion by eliminating other alternative hypotheses for a compact star, such as a concentration of neutron stars or stellar black holes formed by stellar collapse. The high resolution of the images taken by Hubble was necessary to accomplish this feat by observing point stars in orbit and precisely measuring their positions and velocities. Only 35 light years.

In a NASA statement, Eduardo Vitral notes on the matter: “ We are convinced that we have a very small region with a lot of concentrated mass. It is three times smaller than the dense black hole we have previously detected in other globular clusters. When we consider a collection of black holes, neutron stars and white dwarfs separated at the center of the cluster, the region is much more compact than we can reproduce through numerical simulations. They could not create such a perfect concentration of mass. »

The same press release further stated: A group of closely related objects can be dynamically unstable. Unless the object is an intermediate-mass black hole, 40 smaller black holes within a tenth of a light-year distance would be required to produce the observed stellar motions. The consequences are that they merge and/or get kicked out in a game of interstellar pinball. »

Presentation of Hubble’s discovery of M4. Click on the white rectangle in the lower right for a more accurate French translation. English subtitles should appear later. Then click on the nut to the right of the rectangle, then “Subtitles” and finally “Auto Translate”. Select “French”. © NASA’s Goddard Space Flight Center; Lead Producer: Paul Morris; Computer representation of stellar motions at the center of M4: Mattia Libralato (AURA/STScI for ESA)

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