An incredibly energetic phenomenon, almost comparable to the powerful quasars of the early universe, has been identified within the Milky Way itself. Responsible for this event is the star system V4641 Sagittarii (Sgr), located 20,000 light years from Earth. In a relatively short period, it went from being calm to emitting radiation 200 billion times more energetic than visible light.
The only phenomenon comparable to the energy levels of the V4641 Sgr system is a quasar. These are the most powerful radiation shots known to science and, for now, they are only associated with the intense activity of supermassive black holes in the centers of galaxies. The closest recorded quasar to Earth is 780 million light years away. By comparison, V4641 Sgr is barely “in the backyard” and is not linked to Sgr A*, the supermassive black hole located at the center of the Milky Way.
The microquasar that should not shine like its older brothers
The energy record found by the International High Altitude Cherenkov Gamma Ray Observatory (HAWC) challenges current theories about quasars. According to these recent observations, there are alternative sources to supermassive black holes that can expel bursts of ultra-high-energy cosmic radiation. In the absence of more information, the V4641 Sgr phenomenon is currently classified as a microquasar.
The Institute of Nuclear Physics of the Polish Academy of Sciences (IFJ PAN) explains that microquasars are the product of compact binary systems formed by a massive or neutron star and a black hole that absorbs and rotates it. They emit jets of powerful gamma radiation, but never at the level of true quasars, the superluminous events of the universe. There are many microquasars identified within the Milky Way, but the high energy levels of V4641 Sgr are completely anomalous.
“The photons detected by microquasars usually have much lower energies than those from quasars. Typically, we are talking about values on the order of tens of gigaelectronvolts. However, we have observed something quite incredible in the data recorded by the detectors of the observatory: photons from a microquasar in our galaxy that nevertheless carry energies tens of thousands of times higher than typical,” said Sabrina Casanova, one of the co-authors of the study published in Nature.
Astronomers have been closely studying the V4641 system since 1999, when an X-ray burst confirmed that it harbored a black hole. For some years it was considered the closest gravitational phenomenon to Earth. The star that devours that black hole is a class B giant, with three times more mass than the Sun. Any interaction that occurs in that binary system is powerful enough to be compared to the gamma energy shots of a supermassive black hole.
The authors are particularly excited about the find. The radiation from that microquasar will not scatter across the cosmic vacuum as it does with regular quasars. Rather, it will arrive in “short” periods for easy study. In this way it is possible to study the evolution of the first galaxies in the universe in a calm and planned manner.
“The latest discovery demonstrates that, at a relatively small distance from Earth, the mechanisms of jet formation and production of ultra-energetic photons must be operating in a manner analogous to those of the nuclei of active and distant galaxies, on a scale appropriate to the mass of the black hole”, concludes the IFJ PAN.
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