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Post at: Nov 26 2021

Mysterious Radio Waves

Why in the News

  • In October, 2021 astronomers have discovered a transient source of radio waves at the Milky Way’s center. The research paper related to this study was published in The Astrophysical Journal.

Key Findings

  • This report reveals that the center of the Milky Way is a mysterious place. Astronomers think there’s a supermassive black hole there, though it could be dark matter instead. 
  • According to this report the region is densely packed with stars, dominated by red giants. 
  • And because of all the dust between Earth and the galactic center, anybody can’t see anything with visible light, ultraviolet light, or low-energy x-rays.
  • Even then anybody can detect radio waves, and there are some unexplained ones coming from the center of the galaxy, and adding to the mystery, the report indicates.
  • Scientists found ASKAP J173608.2-321635 looking towards the center of the Galaxy.
  • Notably, this object was unique in that it started out invisible, became bright, faded away, and then reappeared. This behavior was extraordinary.
  • Property of the new signal- 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. 
    • The brightness of the object also varies dramatically, by a factor of 100, and the signal switches on and off apparently at random. 


  • The team detected six radio signals from the object over the course of nine months. 
  • When they searched for the object in visible light, they didn’t find anything. 
  • So they decided to try detecting the object with another radio telescope in Australia, the Parkes Observatory. They found nothing.
  • Undeterred, the team performed follow-up observations with the MeerKAT radio telescope in South Africa, which is even more sensitive. They kept checking with the MeerKAT to see if the intermittent signal would show up again.
  • The team then tried the more sensitive MeerKAT radio telescope in South Africa. Because the signal was intermittent, scientists observed it for 15 minutes every few weeks, hoping that they would see it again.
  • This image of the central part of the Milky Way shows a region of 1000 x 500 light years and was taken with the MeerKAT telescope stationed in South Africa.
  • Luckily, the signal returned, but scientists 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 their previous ASKAP observations. 

What Are Radio Waves?

  • Radio waves have the longest wavelengths in the electromagnetic spectrum. 
  • They range from the length of a football to larger than the Earth. 
  • Scientist Heinrich Hertz (German physicist) proved the existence of radio waves in the late 1880s. He used a spark gap attached to an induction coil and a separate spark gap on a receiving antenna. 
  • When waves created by the sparks of the coil transmitter were picked up by the receiving antenna, sparks would jump its gap as well. 
  • Hertz showed in his experiments that these signals possessed all the properties of electromagnetic waves.

Radio Emissions in the Solar System

  • Astronomical objects that have a changing magnetic field can produce radio waves. 
  • The radio astronomy instrument called WAVES on the WIND spacecraft recorded a day of bursts of radio waves from the Sun's corona and planets in our solar system.

Radio Telescopes

  • Radio telescopes look toward the heavens to view planets, comets, giant clouds of gas and dust, stars, and galaxies. 
  • By studying the radio waves originating from these sources, astronomers can learn about their composition, structure, and motion. Radio astronomy has the advantage that sunlight, clouds, and rain do not affect observations.
  • Since radio waves are longer than optical waves, radio telescopes are made differently than the telescopes used for visible light. 
  • Radio telescopes must be physically larger than an optical telescopes in order to make images of comparable resolution. 
  • But they can be made lighter with millions of small holes cut through the dish since the long radio waves are too big to "see" them. 

Milky Way Galaxy 

  • It is a large spiral system consisting of several hundred billion stars, one of which is the Sun. 
  • It takes its name from the Milky Way, the irregular luminous band of stars and gas clouds that stretches across the sky as seen from Earth. 
  • Although Earth lies well within the Milky Way Galaxy (sometimes simply called the Galaxy), astronomers do not have complete understanding of its nature as they do of some external star systems. 

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