Artist’s impression of the oscillating, variable radio signal ASKAP J1736082-321635 coming to Earth from towards the center of the MilkyWay Credit: Sebastian Zentilomo/University of Sydney
The center of the Milky Way is a strange location. Astronomers believe there’s a supermassive great void there, though it might be dark matter rather. The area is largely loaded with stars, controlled by red giants. And since of all the dust in between Earth and the stellar center, we can’t see anything with noticeable light, ultraviolet light, or low-energy x-rays.
But we can identify radio waves, and there are some unusual ones originating from the center of the galaxy, and contributing to the secret.
Astronomers have actually found a short-term source of radio waves at the Milky Way’s center. The group of scientists provided their findings in a paper entitled “Discovery of ASKAP J173608.2–321635 as a Highly Polarized Transient Point Source with the Australian SKA Pathfinder.” The lead author is Ziteng Wang, aPh D. trainee in the School of Physics at the University ofSydney The paper is released in The Astrophysical Journal
The group understood they ‘d discovered something amazing. “Looking towards the center of the Galaxy, we found ASKAP J173608.2-321635, named after its coordinates,” stated co-author Professor TaraMurphy “This object was unique in that it started out invisible, became bright, faded away, and then reappeared. This behavior was extraordinary.”
“The strangest property of this new signal is that it is has a very high polarisation. This means its light oscillates in only one direction, but that direction rotates with time,” stated lead authorWang “The brightness of the object also varies dramatically, by a factor of 100, and the signal switches on and off apparently at random. We’ve never seen anything like it.”
What is it? There are great deals of various kinds of variable stars and things in the sky. They give off variable light all throughout the spectrum.
Could it be a low-mass star or a substellar item? Could it be a pulsar or a short-term magnetar? According to the authors, none of those possibilities matches the observations.
“At first we thought it could be a pulsar – a very dense type of spinning dead star – or else a type of star that emits huge solar flares. But the signals from this new source don’t match what we expect from these types of celestial objects,”Mr Wang stated. The item is extremely polarized, much like a pulsar, however the group didn’t identify any pulsations in their information.
They likewise thought about magnetars as the source, which are neutron stars with severe electromagnetic fields. But the information didn’t match with what we understand about magnetars either. “All radio magnetars show very high degrees of polarization, but their flat radio spectra, in contrast to what we see for ASKAP J173608.2?321635, makes a magnetar an unlikely interpretation,” they compose in their paper.
This image from the research study reveals the place of the variable radio source and other things in the stellar center. The yellow shapes reveal the ASKAP detection, while the cyan contours reveal the MeerKAT detection. The best-fit positions from ASKAP and MeerKAT are revealed as yellow + and cyan × signs, respectively. Red inverted Y signs reveal the sources from the VVV brochure, a study of variables in the infrared. The red Gemini star is a popular source discovered with the GeminiObservatory Credit: Wang et al, 2021
The group identified 6 radio signals from the item throughout 9 months. When they looked for the item in noticeable light, they didn’t discover anything. So they chose to attempt spotting the item with another radio telescope in Australia, the ParkesObservatory They discovered absolutely nothing.
Undeterred, the group carried out follow-up observations with the MeerKAT radio telescope in South Africa, which is much more delicate. They kept talking to the MeerKAT to see if the periodic signal would appear once again. “We then tried the more sensitive MeerKAT radio telescope in South Africa. Because the signal was intermittent, we observed it for 15 minutes every few weeks, hoping that we would see it again,” statedDr Murphy.
This picture of the main part of the Milky Way reveals an area of 1000 x 500 light years and was taken with the MeerKAT telescope stationed in South Africa, a system including 64 radio antennas. © SARAO
They got fortunate. The signal returned. But not in such a way that they anticipated.
“Luckily, the signal returned, but we found that the behavior of the source was dramatically different – the source disappeared in a single day, even though it had lasted for weeks in our previous ASKAP observations,” stated Murphy.
Detecting the short-term signal was an increase for the group, however it didn’t assist them recognize the nature of the source. The group believed it might be a kind of item called a Galactic Center Radio Transient (GCRT). The brand-new item was identified just 4 degrees from the stellar center. It shared some resemblances with a GCRT, however the issue is astronomers do not understand precisely what a GCRT is, either.
“The information we do have has some parallels with another emerging class of mysterious objects known as Galactic Centre Radio Transients, including one dubbed the ‘cosmic burper’,” statedMr Wang’s co-supervisor, Professor David Kaplan from the University of Wisconsin-Milwaukee
“While our new object, ASKAP J173608.2-321635, does share some properties with GCRTs there are also differences. And we don’t really understand those sources, anyway, so this adds to the mystery.”
This is a composite infrared picture of the Milky Way’s stellar center. It reveals brand-new information in intricate structures in the hot ionized gas swirling around the main 300 light-years. Credit: Hubble: NASA, ESA, and Q.D. Wang (University of Massachusetts, Amherst); Spitzer: NASA, Jet Propulsion Laboratory, and S. Stolovy (Spitzer Science Center/Caltech)
For now, the brand-new item will stay a secret. Future centers will have more power and level of sensitivity. The Australian SKA itself is simply one piece of the ultimate Square Kilometer Array, a worldwide radio interferometer that will be consisted of countless meals worldwide. It needs to be online in the next years.
“Within the next decade, the transcontinental Square Kilometer Array (SKA) radio telescope will come online. It will be able to make sensitive maps of the sky every day,” Professor Murphy stated. “We expect the power of this telescope will help us solve mysteries such as this latest discovery, but it will also open vast new swathes of the cosmos to exploration in the radio spectrum.”
Future research studies will discover more information on this brand-new item and others like it. Will it end up being a Galactic Center Radio Transient?
“ASKAP J173608.2?321635 is further notable for its location toward the GC, although we do not yet know whether that is a coincidence or if that location is related to its nature: similar questions could be raised about the GCRT sources. Future comprehensive searches will quantify the exact number of such sources at different locations in the sky,” the authors compose.
Originally released on Universe Today.
For more on this discovery:
Reference: “Discovery of ASKAP J173608.2-321635 as a Highly-Polarized Transient Point Source with the Australian SKA Pathfinder” by Ziteng Wang, David L. Kaplan, Tara Murphy, Emil Lenc, Shi Dai, Ewan Barr, Dougal Dobie, B. M. Gaensler, George Heald, James K. Leung, Andrew O’Brien, Sergio Pintaldi, Joshua Pritchard, Nanda Rea, Gregory R. Sivakoff, B. W. Stappers, Adam Stewart, E. Tremou, Yuanming Wang, Patrick A. Woudt and Andrew Zic, 12 October 2021, The Astrophysical Journal
DOI: 10.3847/1538-4357/ a/c2360
