Strange galactic radio signal has puzzled astronomers

An artist's interpretation of the radio signal in the form of a corkscrew.

Over the course of 2020, astronomers in Australia detected a mysterious batch of radio waves coming from somewhere near the center of the planet. galaxy. But when the team aimed and trained a more sensitive instrument at the source, they detected it only one more time before it disappeared, behaving differently than it had before. The signal is described in an article published in Astrophysical Journal.

“The strangest property of this new signal is that it has a very high polarization. This means that its light oscillates in only one direction, but that direction rotates over time, ”said Ziteng Wang, an astrophysicist at the University of Sydney and lead author of the new study, in a release of the University. In other words, the radio waves were heading to Earth intermittently, without any kind of rhythm or motive. And since they were spotted, the trail has gone cold.

The signal was discovered using a system on Australia’s square kilometer array Pathfinder (Australian Square Kilometer Array, or ASKAP), a radio telescope based in extremely remote Western Australia. The mysterious object that produced the signal was named ASKAP J173608.2-321635, after the telescope that found it and its coordinates in the sky.

“This object was unique in that it started out invisible, turned bright, faded, and then reappeared. This behavior was extraordinary, ”said Tara Murphy, also an astrophysicist at the University of Sydney and a co-author of the paper, in the same statement.

When the radio source was turned off, the team checked the visible light spectrum and found nothing. They also used a radio telescope different, which also found nothing. But later, using the MeerKAT radio telescope in South Africa, the team finally saw the object again, but it disappeared within a day. Researchers have not seen him since.

The Milky Way seen from Uruguay.  The radio source came from near the galactic center.

The Milky Way seen from Uruguay. The radio source came from near the galactic center.
Photo: MARIANA SUAREZ/AFP (Getty Images)

“As for why a source would stop emitting, it could be something related to instabilities in the magnetic field. Magnetic fields can become entangled and then release energy in bursts, ”said David Kaplan, a co-author of the paper and an astrophysicist at the University of Wisconsin-Milwaukee, in an email to Gizmodo. “This happens with our Sun, with magnetars and with other types of objects. So, it is not so much that it stopped broadcasting, since it only broadcasts sporadically (most of the time it is offO)”.

Researchers have some ideas as to what the radio source might have been, but aren’t sure about any of them. The radio wave pattern has similarities to a class of objects called Radio Transients of the Galactic Center, although it also has some differences. The Galactic Center Radio Transients are not a specific object, but rather a group of radio-emitting objects around the center of the Milky Way that do not have a certain identity.

Due to the characteristics of its burst, the team initially thought that ASKAP J173608.2-321635 could be a pulsar, a rotating dead star whose brightness varies regularly for observers on Earth. But this object’s brightness fluctuations were not regular, and its lack of other electromagnetic waves meant that it did not resemble a small brown dwarf star or a magnetar highly magnetic. It may have been a “strange” pulsar, Kaplan said, but the team won’t know for sure with their current data.

Even if ASKAP J173608.2-321635 is not seen again, they expect future observations to determine if the object was the rule or the exception, that is, if the source is the first of a class of objects not observed so far or something. different.

Rather than jump from one radio telescope to another in the future, the team hopes to use the Square Kilometer Array (SKA), the world’s largest radio telescope with 130,000 antennas, for your future observations of distant radio sources. The matrix is ​​expected to begin routine scientific observations towards the end of this decade.

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