More observations and computer simulations are needed to establish which of the two situations is responsible for the polarized light, as well as how rare it is, he noted.
“This is very exciting because it suggests that reality may be more complicated than we thought,” said Giorgos Leloudas, a researcher at the National Space Institute at the Technical University of Denmark who was not involved in the new study. “Tidal disruption events could produce emissions in a variety of ways.”
Black holes are known for devouring stars that come too close while lurking in the deepest reaches of space. However, astronomers have only had a basic comprehension of that tremendous process.
This is clarified by a recent study. Scientists have discovered streams of star material that collided with one another as they circled black holes. These collisions have long been theorized, but the latest discoveries offer a clear glimpse at the beginnings of disk formation surrounding black holes.
“It’s a cool result,” said Dheeraj Pasham, an MIT Kavli Institute for Astrophysics and Space Research research scientist who wasn’t involved in the current work. This type of research “opens a new window into the detailed physics of how exactly a massive black hole eats a star.”
Black holes aren’t observable unless they’re consuming surrounding stars, so scientists keep an eye out for what’s known as a tidal disruption event (TDE), which is when a black hole rips a star apart. One of the only ways for astronomers to discover a black hole is by the use of optical, X-ray, and radio telescopes to detect the characteristic light that is emitted by the disk of extremely hot material that surrounds the object.
Even though optical light from accretion disks has long been observed, its origin “is a big puzzle,” according to scientist Dacheng Lin of Northeastern University, who wasn’t involved in the new work.
Astronomers have struggled to determine if the light is from star matter in the disk-forming stage or star matter being eaten by a black hole.
A team examining a TDE known as AT 2020mot has discovered considerable evidence for the former notion. A supermassive black hole 3.6 million times more massive than our sun has murdered an unhappy star over 900 million light-years from Earth in the galaxy WISEA J003113.52+850031.8. Both were spotted in 2020(opens in new tab) and have yet to be identified. According to astronomers, the wrecked star emits powerful visual emissions as a result of several streams of its material orbiting the black hole and colliding with themselves.
“We anticipate that the stream will gradually circularize and essentially become the accretion disk.” “Eventually, it will be consumed by the black hole,” said Yannis Liodakis, a primary author of the new study and a researcher at the Finnish Center for Astronomy at the European Southern Observatory. “The accretion disk is just an intermediate step.”
The streams took 43 Earth days to circle the black hole and smash, according to Liodakis’ team. Such occurrences are not uncommon, and are even expected once stars are disturbed and accretion disks form.
“The expectation is that once we have stream collisions, this is what initiates the process of a disk forming,” said Fulya Krolu, a Northwestern University graduate student who was not involved in the latest work.
Her previous research discovered that mid-sized black holes consume stars like messy kids, eating some and discarding the rest. “I think we should expect the classic scenario here,” Krolu added, “where roughly half the star becomes bound to the black hole, and the other half is ejected to infinity.”
The current study’s researchers also determined how polarized the detected light is. (Polarized light has waves that oscillate in the same direction rather than in random directions like “normal” light.) The light was polarized to an unusual degree (25%), much to the amazement of the team. This is much higher than the 2% discovered in a few previous investigations of accretion disks elsewhere in the universe.
Lower polarization values can be explained by a variety of physical processes, but “there are very few things in the universe that can make highly polarized light,” according to Liodakis.
A relativistic jet ejected from a black hole, for example, stirs material around the black hole and occasionally ejects it into the surrounding void. As a result, the researchers searched for relativistic jets using the Karl G. Jansky Very Large Array, a radio astronomy observatory facility in New Mexico. They couldn’t find any. Instead, the team’s models suggest that the highly polarized light is caused by shocks formed by many colliding streams of star material, according to the new study.
Light is polarized when it is emitted in magnetic pockets of space, just as some sunglasses polarize sunlight by filtering some of it to lessen glare. The damaged star’s magnetic field may have accelerated particles enough around the black hole analyzed in the current work to emit synchrotron radiation, which is naturally polarized to the high numbers measured. Alternatively, the magnetic field itself could be “stretched along the stream,” resulting in excessive polarization, according to Liodakis.
More observations and computer simulations are needed to establish which of the two situations is responsible for the polarized light, as well as how rare it is, he noted.
“This is very exciting because it suggests that reality may be more complicated than we thought,” said Giorgos Leloudas, a researcher at the National Space Institute at the Technical University of Denmark who was not involved in the new study. “Tidal disruption events could produce emissions in a variety of ways.”
