As mysterious as rapid radio bursts (FRBs), they are now so common that they risk becoming commonplace. But the newly discovered signal deepens the mystery with a few quirks – it comes from an unexpected area of space, and its pulses are about a million times shorter than most, which may indicate that many others like him go unnoticed.
Rapid radio bursts live up to their name – they are vigorous flashes of radio signals from outer space, lasting only milliseconds. Thousands of FRBs have been discovered since their first identification in 2007, some of them have been discovered one-time activities and others repeating either randomly or in a predictable rhythm. Although their origins are still unclear, each new discovery adds more clues – and this latest finding brings a lot to the table.
In January 2020, a second signal from the constellation Ursa Major was detected. For a new study, astronomers investigated its source using 12 parabolic antennas from the EVN observation network. They were able to track the FRB to the edges of the spiral galaxy Messier 81, located about 12 million light years from Earth. This may seem distant, but it is two steps away from the many millions or billions of light years that most FRBs take to reach us.
In this galaxy, the signal came from a globular cluster, a dense group of ancient stars – and this is surprising because most FRBs have been found in areas where the stars are much younger. The main suspect behind the FRB is a type of star known as Fr. magnetar, a small, dense, highly magnetized nucleus that remained after the explosion of a massive star in the form of a supernova. But these magnetars must be very rare in globular clusters.
“Strange things have been going on for billions of years,” said Franz Kirsten, one of the study’s lead authors. “We suspect we’re looking at a star with an unusual history.”
This would not be a running magnet – the team believes that the object in question was once a white dwarf in the binary system. As he spun tightly around his partner, he began to tear material from another star until he gained too much mass and fell into the magnetar. Although this scenario would be rare, the team says it is the easiest way to produce rapid radio bursts in a ball cluster. Interestingly, this may be the first evidence of a magnetar born of a white dwarf that has so far only been described theoretically.
Upon closer inspection, the team found other oddities in the signals. While most FRB signals last in milliseconds, some lasted only a few tens of nanoseconds, which is a million times shorter. This suggests that the object behind them is quite tiny – perhaps only a few tens of meters wide, compared to the usual 10 km (6 miles) or so.
Researchers believe this may indicate the existence of a whole other category of ultrafast FRBs that current instruments are not listening to.
The study was published in two articles, one of which focuses on the location of the source in a ball cluster, published in the journal Naturewhile another discussed superfast impulses appeared in Astronomy of nature.
Source: Max Planck Institute
An ultra-fast radio burst could open up a new class of space signals
Source link An ultra-fast radio burst could open up a new class of space signals