Dn a study by several institutions, researchers have discovered an object that rotates at 30% of the speed of light around the huge black hole of the Milky Way.
Header image: the supermassive black hole Sagittarius A*, taken by the Event Horizon Telescope Collaboration (EHT) and the hotspot and its orbit shown. (EHT Collaboration, ESO/M. Kornmesser (M. Wielgus))
Researchers have spotted signs of a ‘hot spot’ orbiting Sagittarius A* (the black hole) in a clockwise direction, a finding that could help scientists better understand the enigmatic and dynamic environment from the center of our galaxy.
According to Maciek Wielgus, of the Max Planck Institute for Radio Astronomy in Bonn, Germany, who led the study:
We think we are in the presence of a bubble of hot gas that orbits Sagittarius A* in an orbit similar in size to that of the planet Mercury, but completes a complete loop in just about 70 minutes. This requires mind-boggling speed of about 30% of the speed of light.
…30% of the speed of light is about 90,123 kilometers per second.
The observations were made as part of the Event Horizon Telescope (EHT) collaboration’s campaign to image black holes using the Atacama Large Millimeter/submillimeter Array (ALMA) radio telescope in the Chilean Andes, which is owned by the European Southern Observatory (ESO).
The EHT, which has connected eight active radio telescopes around the world, including ALMA, released the first-ever image of the Milky Way’s black hole in April 2017. Wielgus and his team, who are members of the EHT collaboration, have used ALMA data collected at the same time as EHT observations of Sagittarius A* to calibrate the observation. Unexpectedly, the team found additional clues about the characteristics of the black hole in the ALMA data alone.
Luckily, some of the observations were made shortly after NASA’s Chandra Space Telescope observed an X-ray flare from the center of the Milky Way. These “eruptions”, which have already been observed with X-ray and infrared telescopes, would be linked to hot gas bubbles, called “hot spots”, which orbit very quickly and close to the black hole.
Still according to Wielgus:
What is really new and interesting is that such flares have so far only been clearly present in X-ray and infrared observations of Sagittarius A*. Here we see for the first time a very strong indication that orbiting hotspots are also present in radio observations.
ALMA allows astronomers to study polarized radio waves from Sagittarius A*, which can be used to uncover the black hole’s magnetic field. Along with theoretical models, the team used these observations to learn more about how the hotspot was created and how it fits into its surroundings. Their research enriches our knowledge of the shape of this magnetic field and helps astronomers learn more about our black hole and its environment.
The Milky Way and the location of its black hole seen from the Atacama Large Millimeter/submillimeter Array (ALMA). (ESO/José Francisco Salgado (josefrancisco.org), EHT Collaboration)
The observations confirm some of what ESO’s Very Large Telescope (VLT) GRAVITY instrument, which observes in the infrared, had previously found. Using the VLT, the team also hopes to be able to directly observe the gas clouds orbiting the black hole, which will allow them to get closer to it and learn more about it.
Hopefully, one day we will be able to claim that we “know” what is going on in Sagittarius A*.
The study published in the journal Astronomy & Astrophysics : Orbital motion near Sagittarius A* and presented on the website of the European Southern Observatory: Astronomers detect a bubble of hot gas swirling around the supermassive black hole of the Milky Way.