The Milky Way Galaxy stretches for 450 thousand light years, and we are somewhere in its backyard (no offense, earthlings). Based on the data available today, our planet is located in a so-called local bubble, that is, inside an elongated gas cloud formed by particles of ancient supernovae. This bubble stretches over 300 light years and sits at the inner edge of one of the spiral arms of our Galaxy. However, it is hardly possible to estimate our exact location - we simply do not have the opportunity to look at the galaxy from the outside. But something is available to us, namely - observation of the center of the Milky Way, which is located 25,800 light-years from us, according to the latest estimates. The galactic center, as the astronomical community calls it, is the galactic spinning center that houses a supermassive black hole. But beyond this cosmic monster, the center's inhabitants are dense stellar superclusters, including red giants, supergiants, extremely hot gas, and abundant radio signal sources. One of them, and quite unusual, was recently discovered by astronomers.
Listening to the Milky Way
It may seem surprising, but until 1933 there was no such science as radio astronomy. Moreover, the discovery of radio waves coming from the galactic center was completely accidental. For example, engineer Karl Jansky worked on the interference that was observed during the development of the world's first telephone system, Alexander Bell. The problem was that when trying to make a call across the Atlantic Ocean, people heard a hissing sound on the other side of the wire instead of each other.
Finding out the cause of the problem, Jansky came to the conclusion that the noise is radio waves that emanate from the center of the galaxy, disrupting telephone communications and creating interference. Almost 88 years have passed since that moment, but now we know incomparably more about space and the Universe.
Radio astronomy has allowed us to look into places that are too dark for the human eye, but these areas literally glow in radio waves.
Modern telescopes are capable of capturing a wide variety of waves - from light waves and gamma radiation to radio waves, which have allowed scientists to draw up a fairly detailed map of the observable universe. It should be noted that radio waves are predominantly emanating from distant galaxies and very cold stars, allowing astronomers to look into the darkest regions of the cosmic ocean.
Looking for radio waves
Aiming a radio telescope at a space object, radio waves hit the surface of the instrument, which is a kind of mirror for radio waves and can be metal with holes inside (mesh), or solid metal, such as aluminum.
The first mirror directs radio waves to a second "radio mirror", which then directs them to a place called the "receiver." This part of the radio telescope picks up radio waves and turns them into an image. Basically, a receiver does the same thing as a camera: converts radio waves into a picture.
The data collected by the latest radio telescopes have already allowed astronomers to create the most complete catalog of radio bursts to date. Let me remind you that fast radio bursts (FRBS) are very short but intense pulses of radio waves recorded in the radio range of the electromagnetic spectrum. These impulses last only a few milliseconds, and then disappear without a trace.
For the first time, fast radio multiplexes were in 2007 and still remain a mystery to the scientific community.
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A new object in the center of the Milky Way?
Recently, according to the portal Space.com, astronomers discovered a strange radio source emanating from somewhere in the center of our Galaxy. The signal repeats, seemingly randomly, so it cannot be clearly attributed to any known astronomical object.
The signal was first captured in data from April 2019, collected using the Australian Pathfinder radio interferometer (ASKAP). This huge telescope scans the sky looking for repetitive sources of radio emission that may be associated with objects and phenomena such as pulsars, supernovae, gamma-ray bursts and stellar flares.
But the new radio signal does not match any of the known space objects. Designated by ASKAP as J173608.2-321635 and originating from the galactic center, the signal repeats at apparently random intervals.
Earlier, with the help of ASKAP, scientists created a "new atlas of the Universe", on which three million galaxies were plotted
Until now, scientists have relied on gamma rays, X-rays, infrared radiation and radio waves among other means to study the Galactic Center. The stardust around the galactic disk hides a massive stellar population at the center of the Milky Way, so invisible wavelengths such as infrared are used to unravel its secrets. But while radio telescopes are the best way to study the galactic center, the new discovery has puzzled scientists.
In a work that has not yet been peer-reviewed and published on the airxiv preprint server, astronomers have compared the new signal to low-mass stars; dead stars emitting electromagnetic radiation (pulsars); neutron stars with strong magnetic fields and an elusive class of objects called Galactic Center Radio Transitions (GCRTs). Surprisingly, the J173608.2-321635 signal does not meet the characteristics of any of the above objects, which makes it potentially new.
According to the authors of the study, the unusual source showed constant radio signal emission for several weeks, but then quickly turned off within just one day. A sharp change in the emission of a radio signal makes it especially difficult to constantly observe it for a more detailed assessment.
Most likely, the new radio signal indicates the existence of completely unfamiliar objects in the galactic center.
Interestingly, the radio signals sent by the mysterious object are unparalleled in the infrared or X-ray wavelength range, which suggests that it almost looks like a ghost in the electromagnetic spectrum and is extremely difficult to detect, astronomers report.
Interestingly, the three sources of similar GCRTs discovered so far bear some resemblance to the mysterious signal, but the emission pattern of ASKAP J173608.2-321635 is different, and the time scale of radio visibility also varies. Ultimately, astronomers believe that a completely new class of objects detected with radio telescopes could be the source of the new radio signal. However, if this source is a GCRT, then it defies everything scientists know about them.