Astronomers have spotted a mysterious object, which they imply could be a massive hot bubble of gas orbiting the black hole at the center of the Milky Way every seventy minutes. This means that the object is traveling at a mind-blowing velocity of about 30% of the speed of light.
Observations by the Atacama Large Millimeter/submillimeter Array (ALMA) have allowed astronomers to spot something odd next to the supermassive black hole at the center of the Milky Way. According to astronomers, there is a mysterious object, a hot spot that revolves around Sagittarius A*. Researchers say the discovery will help better our understanding of the strange yet dynamic environment.
According to the researchers, the object that circles the black hole is likely to be a hot bubble of gas, and it revolved around Sagittarius A* in orbit similar in size to that of the planet Mercury. The only difference is that it completes an entire orbit in just around seventy minutes.
In other words, this means that this enigmatic object requires a mind-blowing velocity of about 30% of the speed of light to achieve this orbit in seventy minutes, explains Maciek Wielgus of the Max Planck Institute for Radio Astronomy in Bonn, Germany. Wielgus led the study describing the hot bubble of gas circling the black hole, published in the journal Astronomy & Astrophysics.
During the Event Horizon Telescope (EHT) Collaboration’s campaign to image black holes, ALMA – a radio telescope co-owned by the European Southern Observatory (ESO) – was used to make observations. In April 2017, the EHT linked together eight existing radio telescopes worldwide, including ALMA, and achieved photographing, for the first time ever, the black hole at the center of the Milky Way galaxy, Sagittarius A*. A team of EHT Collaboration members, including Wielgus, used ALMA data acquired simultaneously with the EHT observations of Sagittarius A to calibrate the EHT data. With only ALMA measurements, the team found more clues to the black hole’s nature.
The observations were made shortly after NASA’s Chandra Space Telescope spotted an X-ray flare emitted from the center of our galaxy. There is a theory that these flares may be associated with so-called hot spots, hot gas bubbles orbiting extremely fast and close to black holes. They were previously observed with X-rays and infrared telescopes.
This is really interesting because flares of this kind were previously only observed in X-rays and infrared. Here we see for the first time a very strong indication that orbiting hot spots are also present in radio observations,” says Wielgus.
According to Jesse Vos, a Ph.D. student at Radboud University, who was also involved in this study, these hot spots detected at infrared wavelengths are probably manifestations of the same physical phenomenon: as hot spots that emit infrared become cool, they become visible at longer wavelengths, similar to those observed by ALMA and the EHT.
Recent findings support the theory that flares are caused by magnetic interactions in the very hot gas orbiting near the black hole. It now seems that these flares have a magnetic origin, and the scientific observations provide insight into their geometry. As a result of the new data, we now have the opportunity to develop a theoretical interpretation of these events,” says Radboud University co-author Monika Mocibrodzka.
With ALMA, scientists are able to study polarised radio emissions that originate from Sagittarius A*, and thereby determine the black hole’s magnetic field. In addition to these observations, the team used theoretical models to investigate the hot spot’s formation and its environment, including the magnetic field surrounding Sagittarius A*. In the process of uncovering the nature of our black hole and its surroundings, their research provides stronger constraints on the shape of this magnetic field than previous observations.
ESO’s Very Large Telescope (VLT)’s GRAVITY instrument, which peers into the cosmos in infrared, has confirmed some of the previous discoveries. Both GRAVITY and ALMA data suggest the flare originates in a cluster of gas swirling around the black hole clockwise at about thirty percent the speed of light. Scientists also note that the hot spot’s orbit is nearly face-on.
It would be a true milestone for our understanding of the physics of flares in the Galactic center to be able to track hot spots at multiple wavelengths using GRAVITY and ALMA coordinated multiwavelength observations in the future,” Ivan Marti-Vidal of the University of Valencia, a study co-author, says.
In addition, the EHT team hopes to directly observe the gas clumps orbiting the black hole, enabling them to probe closer to the object and gain a deeper understanding.
What goes on near the cosmic environment of Sagittarius A* is a mystery to experts. However, Wielgus hopes that one day we will finally get to know more about it and paint a better picture of what goes on at the center of our galaxy.
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