And it looks like they are caused by a magnetar.
A few months ago, tensions within the astronomical community ran high. Scientists had namely mysterious observed fast radio bursts that appeared to be from our own galaxy. The researchers hypothesized that they came from a nearby magnetar. At the time, however, they were still close by. But now the suspicions appear to be true. The findings have been published in the journal Nature.
Fast radio bursts
Fast radio bursts are enormous bursts in space, releasing a huge amount of energy in a short time. In very concrete terms, these are often eruptions where more energy is released in 1 millisecond than our sun generates in 80 years. The first high-speed radio flash was discovered in 2007. Since then, many more fast radio bursts have been found all over the universe.
Close to
How exactly did these flashes originate? Nobody knew. The mysterious radio bursts often came from such distant corners of the universe that it was difficult to reveal their source. But the current research is now shedding light on the veil. Because for the first time, researchers have observed fast radio bursts coming from our own Milky Way. They are therefore the closest fast radio bursts detected to date. This suddenly made it a lot easier for the research team to locate the source.
Magnetar
The astronomers picked up signals from the fast radio bursts using the Dominion Radio Astrophysical Observatory’s CHIME radio telescope. And it appears that the observed radio pulses were produced by a magnetar called SGR 1935 + 2154 (see box). “If it came from another object near the magnetar, it would be a very big coincidence,” says researcher Kiyoshi Masui.
What is a magnetar?
Magnetars are in fact very rare neutron stars – the super-compact remnants of exploded massive stars. A neutron star rotates quickly, has a strong magnetic field and a diameter of about 20 kilometers, but a mass larger than the sun. Magnetars are young neutron stars with an exceptionally powerful magnetic field. They are quite rare: only a few dozen of them have been discovered to date. The existence of magnetar SGR 1935 + 2154 was revealed six years ago and represents one of the few magnetars in our Milky Way. SGR 1935 + 2154 is located near the center of the Milky Way and is about 30,000 light-years away from Earth. Although the magnetar was regarded as ‘normal’ magnetar, it now turns out to be a bit more unusual than expected.
To further figure this out, the researchers studied the brightness of the magnetar at the moment it would have generated the observed radio bursts. And this shows that when the fast radio flash appeared in the split second, the magnetar became 3000 times brighter than any other radio signal from a magnetar. And that’s interesting. Although physicists have theorized that magnetars can produce fast radio bursts, this is the first time scientists have actually had direct, observational evidence that magnetars are indeed sources of fast radio bursts. And that means that researchers have now discovered the origin of fast radio bursts for the first time. “There is a great mystery as to what could cause these major bursts of energy,” said researcher Kiyoshi Masui. “But this is the first time that we can link these exotic fast radio bursts to a single astrophysical object.”
How?
Now that magnetars have been shown to be able to produce fast radio bursts, the question remains: how? While there are numerous theories, scientists still don’t understand exactly how fast radio bursts are generated in the universe and, in particular, how magnetars might produce them. In addition, other sources of radio flashes may also exist, because different detected signals behave very differently. Moreover, we know that fast radio bursts come in two ‘flavors’: there are one-off and repeating radio bursts. It is still unclear whether these two ‘types’ of radio bursts have the same origin or are in fact two completely different phenomena.
SGR 1935 + 2154, however, appears to have emitted radio bursts several times. After the first radioflashes emitted were detected, researchers found that the same magnetar produced another radioflashes, though not nearly as intense as the original flashes. “The magnetar has done some interesting things and we are now trying to find out what it all means,” says Masui. “We also keep an eye on other magnetars. But the important thing now is to study this one source closely to see what it tells us about the emergence of fast radio bursts. ”
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