A little dead star that dazzled us earlier this year isn't through with its shenanigans.
Magnetar SGR 1935+2154, which in April emitted the primary known fast radio burst from inside the Milky Way, has flared up all over again, giving astronomers one more chance to unravel over one major cosmic mystery.
On 8 October 2020, the CHIME/FRB collaboration detected SGR 1935+2154 emitting three-millisecond radio bursts in three seconds. Following abreast of the CHIME/FRB detection, the FAST radio reflector found something else - a pulsed radio wave in keeping with the magnetar's spin period.
"It's really exciting to work out SGR 1935+2154 back again, and i am optimistic that as we study these bursts more carefully, it'll help us better understand the potential relationship between magnetars and fast radio bursts," astronomer Deborah Good of the University of British Columbia in Canada, and member of the CHIME/FRB, told ScienceAlert.
The detections, reported within the Astronomer's Telegram, are currently undergoing analysis.
Before April of this year, fast radio bursts (FRBs) had only ever been detected coming from outside the galaxy, usually from sources lots of light-years away. the primary one was discovered in 2007, and ever since, astronomers are trying to work out what causes them.
As the name implies, FRBs are bursts of extremely powerful radio waves detected within the sky, some discharging more energy than many various Suns. They last mere milliseconds.
Because most fast radio burst sources seem to flare once and haven't been detected repeating, they're extremely unpredictable. additionally, those we've detected usually come from up to now away, our telescopes are unable to choose out individual stars. Both of those characteristics make FRBs challenging to trace down either to a precise source galaxy, or a known cause.
But SGR 1935+2154 is barely around 30,000 light-years away. On 28 April 2020, it spat out a robust millisecond-duration burst, which has since been named FRB 200428 keep with fast radio burst naming conventions.
Once the ability of the signal was corrected for distance, FRB 200428 was found to be virtually as powerful as extragalactic fast radio bursts - but everything else about it fit the profile.
"If the identical signal came from a close-by galaxy, like one among the nearby typical FRB galaxies, it might appear as if an FRB to us," astronomer Shrinivas Kulkarni of Caltech told ScienceAlert in May. "Something like this has never been seen before."
We don't know much about the three new bursts yet. Because scientists are still engaged on the information, it's possible that some early conclusions are likely to alter, Good told ScienceAlert. But we are able to already tell that they're both like and in contrast to FRB 200428.
They are a bit less powerful again, but they're all still incredibly strong, and everyone just milliseconds long. "Although less bright than the detection earlier this year, these are still very bright bursts which we'd see if they were extragalactic," Good said.
"One of the foremost interesting aspects of this detection is that our three bursts seem to own occurred within one rotation period. The magnetar is understood to rotate once every ~3.24 seconds, but our first and second bursts were separated by 0.954 seconds, and therefore the second and third were separated by 1.949 seconds. That's a small amount unusual, and that I think it's something that we'll be looking into further going forward."
That could reveal something new and useful about magnetar behavior, because - let's face it - they're pretty weird.
Magnetars - of which we've only confirmed 24 up to now - are a sort of neutron star; that is the collapsed core of a dead star not massive enough to show into a part. Neutron stars are small and dense, about 20 kilometers (12 miles) in diameter, with a maximum mass of about two Suns. But magnetars add something else to the mix: a surprisingly powerful field of force.
These jaw-dropping fields are around a quadrillion times more powerful than Earth's field of force, and m times more powerful than that of a traditional star. and that we still don't fully understand how they got that way.
But we do know that magnetars undergo periods of activity. As gravity tries to stay the star together - and inward force - the force field, pulling outward, is so powerful, it distorts the star's shape. This ends up in ongoing tension which occasionally produces gargantuan starquakes and giant magnetar flares.
SGR 1935+2154 has been undergoing such activity, suggesting a link between magnetar tantrums and a minimum of some FRBs.
Obviously, astronomers have found the source of the primary intra-galactic FRB to be of intense interest. When CHIME/FRB reported their detection, other astronomers visited have a glance at the star, including a team led by Zhu Weiwei of the National Astronomical Observatories of China who had access to FAST, the most important single-aperture astronomical telescope within the world.
And they found something interesting, also reported within the Astronomer's Telegram - pulsed electromagnetic radiation. These radio pulses were nowhere near as strong because the bursts, but they're extremely rare: If validated, SGR 1935+2154 will only be the sixth magnetar with pulsed electromagnetic radiation. and also the pulse period was found to be 3.24781 seconds - almost precisely the star's spin period.
This is curious because to date, astronomers have struggled to search out a link between magnetars and radio pulsars. Pulsars are another form of a neutron star; they need a more normal force field, but they pulse in radio waves as they spin, and astronomers have long tried to work out how the 2 varieties of stars are related.
Earlier this year, Australian astronomers identified a magnetar that was behaving sort of a radio pulsar - a possible "missing link" between the 2, and evidence that a minimum of some magnetars could evolve into pulsars. SGR 1935+2154 might be another piece of the puzzle.
"Based on these results and therefore the increasing bursting activities, we speculate that the magnetar is also within the process of turning into a lively radio pulsar," Weiwei's team wrote.
What an absolutely bloody fascinating little star this is often arising to be.
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