(ORDO NEWS) — There are strange objects lurking in our galaxy, and astronomers have just spotted an unusual object about 3,000 to 4,000 light-years away.
By examining the mysterious flashes of light emanating from this system, scientists have discovered what they believe is the elusive “black widow” star – a rapidly spinning pulsar that is sustained by slowly devouring its smaller companion star.
Pulsars of the “black widow” type are extremely rare – no more than a dozen of them are known in the Milky Way. But this pulsar appears to be one of the most extreme, and perhaps the strangest, examples of this phenomenon we have ever found.
Named ZTF J1406+1222, this binary system has the shortest orbital period ever observed, with a black widow and its prey orbiting each other every 62 minutes.
Even more unusual is that there appears to be a third, distant star in the system that takes about 12,000 years to orbit the other two.
This system is truly unique among black widows because we detected it in visible light, because of its wide companion, and because it came from the galactic center,” says lead researcher and physicist Kevin Burge from the Department of Physics. Massachusetts Institute of Technology.
Pulsars are created when the cores of massive supergiant stars decay into neutron stars. When these neutron stars are highly magnetized and rotate rapidly, they become what we call a pulsar.
Like super-bright beacons in the universe, pulsars spin very fast and shine X-rays and gamma rays at us at intervals ranging from more than one second to periods as long as milliseconds. Pulsars usually spin fast and die young due to the amount of energy they release.
But if a passing star gets close enough, the pulsar can slowly suck material out of it like a giant parasite, sucking out enough energy to keep spinning and feeding off another star until it devours it.
These systems are called “black widows” due to the fact that the pulsar, as it were, absorbs what recycles it, similar to how a spider eats its friend, “says Burge.
In the past, astronomers learned about these “black widow” systems from gamma rays or X-rays, high-frequency radiation emitted by the pulsar itself.
But to find ZTF J1406+1222, the team used a new technique: They looked for visible light coming from the star being eaten.
It turned out that the “day” side of the companion star with which the “black widow” is associated can be many times hotter than the “night” side, and this extreme change in brightness can be detected.
To test this idea, the researchers used data from the Zwicky Transient Facility Observatory in California and were able to find the black widow systems we already know about, confirming the technique’s work.
Then they searched for new “black widows” and stumbled upon ZTF J1406+1222, where the companion star changes brightness 13 times every 62 minutes.
This is the first time a black widow pulsar has been found in this way, and that is what makes its discovery so exciting.
The other part, of course, is the mysterious system they stumbled upon.
Not only is the black widow pulsar and its victim trapped in the tightest cannibalistic spiral known to date, but when the team turned to measurements of the star with the Sloan Digital Sky Survey, they saw a rare, cold, subdwarf star trailing behind the system. with low metallicity, which, as it turned out, revolves around the binary only once every 12,000 years.
The presence of this distant third star could make the system an unheard-of “triple” black widow, and astronomers are puzzled over how this system could even have formed.
Based on current observations, Burge and his colleagues have a few ideas. Black widow binars arise from a dense cluster of old stars known as a globular cluster.
One of the leading hypotheses is that if this particular cluster drifted into the center of the Milky Way, then the gravity of our central black hole could have torn the cluster apart, sparing only the triple black widow.
“It’s a complicated birth scenario,” Burge says. “This system has probably been floating in the Milky Way longer than the Sun.”
Even stranger, while the team was able to detect ZTF J1406+1222 in visible light, when they turned their attention to gamma and X-rays, they couldn’t see it – suggesting it might not actually be a black widow at all.
“The only thing we know for sure is that we see a star with a day side that is much hotter than the night side, orbiting something every 62 minutes,” says Burge.
Everything points to the fact that this is a binary “black widow”. But it has a few oddities, so maybe it’s something completely new.”
The team plans to continue monitoring the system to better understand what is going on.
It is intriguing that it could be a prime candidate for studying the physics of a neutron star “impact”. Astronomers know that when neutron stars form, they receive a “push” that causes them to accelerate at high speeds.
But it is not entirely clear where this push comes from. The strange story of the birth of this mysterious system may shed light on this question.
“There’s a lot we don’t understand yet. But we have a new way to look for such systems in the sky.”
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