MIT: An unknown third star partner orbits the system, which is thought to have arisen around the heart of the Milky Way galaxy.
Scientists at the Massachusetts Institute of Technology (MIT) have been led to an unknown system 3,000 light-years away by the flashing of a neighbouring star. According to the latest findings, the peculiar stellar anomaly is a new “black widow binary” – a fast spinning neutron star, or pulsar, that is orbiting and slowly eating a smaller companion star, much like the spider named after it does to its partner in the same way.
A total of roughly two dozen black widow binaries have been discovered in the Milky Way, according to scientists. When the pulsar and companion star circle each other every 62 minutes, this newest candidate, designated ZTF J1406+1222, will have the lowest orbital period of any other candidate discovered too far. The system is particularly odd in that it seems to be home to a third, far-flung star that appears to revolve around the two inner stars every 10,000 years, according to the observations.
The possibility of a triple black widow has prompted speculation about how such a system may have come to be. The MIT team offers the following genesis scenario in light of their observations: The triple system, like the majority of black widow binaries, is thought to have formed from a dense constellation of ancient stars known as a globular cluster.
Possibly, this specific cluster travelled towards the core of the Milky Way, where the gravity of the central black hole was strong enough to force the cluster apart, but not enough to destroy the triple black widow’s structure.
“It’s a difficult birth situation,” says Kevin Burdge, a Pappalardo Postdoctoral Fellow in the Department of Physics at the Massachusetts Institute of Technology. “It’s likely that this system has been circling about in the Milky Way for longer than the sun has been in existence.”
A paper by Burdge and his colleagues, published in the magazine Nature, describes the team’s finding in full. The triple system was discovered via the application of a novel technique developed by the researchers. While most black widow binaries are discovered by the gamma and X-ray radiation generated by the core pulsar, the researchers discovered ZTF J1406+1222 using visible light, especially the flashing of the binary’s companion star.
MIT: The Gaia space telescope is seen in this illustration. One of the sources utilised by MIT astronomers in their quest for black widow binaries.
In Burdge’s opinion, “this system is very exceptional as far as black widows go, since we discovered it with visible light, and because of its broad partner, and because it originated from the galactic center,” the astronomer explains. “There’s still a lot we don’t understand about it,” says the researcher. “However, we have developed a novel method of searching for these systems in the sky.”
The study’s co-authors include researchers from a variety of universities, including the University of Warwick, Caltech, the University of Washington, McGill University, and the University of Maryland. The University of Warwick was one of the study’s partners.
DAY AND NIGHT
Pulsars, which are fast spinning neutron stars that are the collapsing cores of huge stars, provide the energy that powers black widow binaries. Pulsars had a dizzying rotating period, whirling about every few milliseconds and emitted bursts of high-energy gamma and X-rays as a result of their rapid circular revolution.
Pulsars are known to spin down and perish swiftly as a result of the massive amount of energy they expend. However, every now and again, a passing star might breathe fresh life into a pulsar. As a star approaches, the pulsar’s gravity pushes material away from the star, releasing additional energy that is used to spin the pulsar back up. It then begins reradiating energy, which further depletes the star’s resources until it is finally destroyed by the star itself.
As Burdge points out, “these systems are dubbed black widows because the pulsar kind of consumes the item that regenerated it, similar to way a spider destroys its spouse,” he explains.
Every black widow binary discovered so far has been identified by the pulsar’s gamma and X-ray flashes, respectively. Burdge discovered ZTF J1406+1222 as a result of the optical flashing of the companion star, which was a world first.
However, it turns out that the day side of the companion star — the side that is always facing the pulsar — may be several times hotter than the night side, owing to the continual high-energy radiation it gets from the pulsar. This is due to a phenomenon known as a radiative transfer.
“I had the idea that instead of going straight for the pulsar, I could attempt looking for the star that it was cooking,” Burdge reveals.
Theorizing on the basis of observations of stars whose brightness changed by a significant amount over time, he concluded that such observations would be a strong indication that the star was in a binary system with the pulsar.
STAR MOTION
Burdge and his colleagues examined optical data collected by the Zwicky Transient Facility, a California-based observatory that captures wide-field photographs of the night sky. The results of their investigation confirmed their hypothesis. They looked for stars whose brightness was changing rapidly by a factor of 10 or more over time, on a timeframe of approximately an hour or less, which would suggest the existence of a companion star circling snugly around the pulsar. They found no such stars.
The team was successful in distinguishing between the dozen known black widow binaries, demonstrating the precision of the novel technique. It wasn’t until after that that they saw a star that altered its brightness by a factor of 13 once every 62 minutes, which indicated that it was most likely part of a new black widow binary, which they named ZTF J1406+1222.
When the MIT students were looking for the star, they used data from the Gaia satellite telescope, run by the European Space Agency. Gaia is a space telescope that takes exact measurements of the location and velocity of stars in the sky. The scientists discovered that the binary was being pursued by another distant star by looking back over decades of measurements of the star taken by the Sloan Digital Sky Survey. Following their calculations, they discovered that this third star looked to be circling the inner binary once every 10,000 years.
Surprisingly, no direct detection of gamma or X-ray emissions from the pulsar in the pair has been made by the scientists, despite the fact that this is the normal method by which black widows are verified. Consequently, ZTF J1406+1222 is regarded a potential black widow binary, which the team intends to confirm with more observations in the future.
According to Burdge, the only thing we can be certain of is that we are looking at a star with a day side that is much hotter than the night side, and that it is circling something every 62 minutes. In my opinion, everything points toward a black widow binary being at work here. However, there are a few odd things about it, so it’s conceivable that it’s something completely else.”
Observations of the new system will continue, along with the use of the optical technology to light other neutron stars and black widows in the sky, said the researchers.
Published By: Ifa Zamzami
