Moving at about 600 kilometers per second through space, the object has captured the attention of scientists around the world. Experts studying the phenomenon speculate that we may be dealing with the first observed hypervelocity star with a very low mass. The trajectory of the stellar “sprinter” indicates that it may be leaving the Milky Way.
The object was spotted as part of the Backyard Worlds: Planet 9 project, which involves thousands of amateur scientists who study data collected over 14 years by the mission. NASA Wide-field Infrared Survey Explorer (WISE). Volunteers tag moving objects in data files, and when enough of them tag the same object, astronomers begin to study it. And so it was in this case. About 80,000 people noticed the celestial body moving incredibly fast. The object was studied by two telescopes in Hawaii. The results of the observations are intended for publication in the journal The Astrophysical Journal Letters.
What is J1249+36?
The object, called J1249+36, is about 400 light-years from Earth and is moving at 0.1 percent of the speed of light. Its small mass makes it difficult to classify. Astronomers wonder whether it might be a low-mass star or a so-called brown dwarf. Brown dwarfs are objects similar to stars but not large enough to convert hydrogen into helium, which is the main source of energy. They are more massive than planets but less massive than stars.
According to study co-author Roman Gerasimov, an assistant professor in the Department of Physics and Astronomy at the University of Notre Dame, calculations suggest that the mysterious object has a mass of about eight percent that of the Sun. “That puts it right at the lower end of the acceptable stellar mass range. In fact, it's possible that the object's mass is slightly below that, which would suggest that it's not a star but a brown dwarf,” he explained. This hypothesis is countered by the fact that brown dwarfs don't follow trajectories that would throw them out of the solar system. the galaxy. Additionally, the data showed that the object has a lower concentration of iron than expected for a brown dwarf.
The object may be a star, according to observations made with the near-infrared spectrograph at the Keck Observatory in Hawaii. The data showed that J1249+36 may be an L-type subdwarf, a class of very low-mass stars with temperatures lower than our Sun.
Very low-mass stars are harder to detect than massive stars because they are colder and less luminous than them. If these assumptions of scientists turn out to be true, it will mean that for the first time a hypervelocity star with a very low mass has been observed. Hypervelocity stars were discovered in 1988, but they are extremely rare to detect.
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Unusual flight trajectory
Astronomers determined the object's position and speed in space, which allowed them to see that at some point it might leave the Milky Way.
J1249+36 is moving at a dizzying speed of 600 kilometers per second. The team of scientists distinguished two scenarios explaining the unusual speed of the potential star. In the first, J1249+36 was originally a companion to a white dwarf (the core of a star that has exhausted its fuel and died). When such objects enter a close orbit, the white dwarf can collect mass from the smaller “companion”. This results in periodic outbursts or, as a consequence, a huge supernova explosion.
“In this type of supernova, the white dwarf is completely destroyed, so its companion is freed and flies away at its original orbital speed, plus a little kick from the supernova explosion,” said Adam Burgasser, a professor of astronomy and astrophysics at the University of California, San Diego.
The second scenario assumes that J1249+36 was part of a globular cluster. Astronomers predict that black holes of different masses are located at the center of such clusters. Black holes can form binary pairs. When an object gets too close to such a system, it can be “catapulted.”
“When a star encounters a binary black hole, the complex dynamics of this three-body interaction can eject the star from the globular cluster,” study co-author Kyle Kremer, an assistant professor in the Department of Astronomy and Astrophysics at UC San Diego, said in a statement.
Further research needed
Scientists are now looking for a “chemical fingerprint” of the unusual object, which could help determine which system J1249+36 came from. The researchers believe the discovery gives astronomers a new opportunity to learn more about the history and dynamics of the Milky Way.
CNN, WM Keck Observatory
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