New clue to FRBs, mysterious radio flashes from space

General Studies Paper 3

CONTEXT

• Mysterious emissions of radio light from the far reaches of the universe are the next big thing in modern radio astronomy. Fleeting flurries of radio waves, called fast radio bursts (FRBs) reach Earth from faraway galaxies, emitting as much energy in a millisecond as-the sundowns over weeks.

FRBS

• We know almost nothing about the precise origins of FRBs and why they appear in such short, sharp bursts – other than that these celestial electromagnetic impulses probably come from the embers of dying stars.
• Some FRBs are ‘one-off’ phenomena: spotted just once and never detected again; others are repeaters, flashing Earth intermittently like some ghostly lighthouse in the depths of space.
• An international team of astronomers has now published the results of its exhaustive study on a repeating FRB from a distant galaxy that offers new clues about the origins of these mysterious radio flashes.
• They targeted a repeating FRB, called FRB 20190520B using the Green Bank Telescope in the U.S. and the Parkes Observatory in Australia, and recorded hundreds of bursts from it.

FINDINGS

• They discovered that the FRB’s Faraday rotation measure – an indicator of its magnetic field strength – was highly variable and that it reversed direction twice.
• This magnetic reversal, they believe, has to do with the FRB source orbiting a binary star system where the companion star is probably a massive star or a black hole.
• They saw that the value of the magnetic field and electron density was also found to vary around this source which indicates a very turbulentmagnetisedplasma environment.

CONCLUSION OF THE FINDINGS

• This conclusion ties in with an older discovery of a strikingly similar binary system in the Milky Way galaxy, including the magnetic field reversal.
• This FRB, called FRB 20190520B, is very similar to other repeating FRBs in energy scales, narrow banded emission, temporal widths etc.
• They concluded that it is possible that all repeating FRBs could be in binaries but differ in their local conditions, like the orbital period or the orbital inclination.
• Constant long-term monitoring of these FRBs is necessary to make a final call on this.
• Cosmologists believe that learning more about such changes in the magnetised environment around FRBs could eventually help track down their origins.
• To do this, astronomers have a whole new generation of radio telescopes at their disposal.

RADIO TELESCOPES

• Until the early 1930s, astronomers depended on the limited visible part of the electromagnetic spectrum to make observations, unaware of the enormous potential of the radio band lying at one end of the spectrum.
• Their long wavelengths allow radio waves to traverse intergalactic space without interruption, making them an ideal tool to identify radio emissions from faraway heat sources.
• Fortunately, scientists pioneering findings endured and inspired others to develop radio astronomy, thanks to which we know about intergalactic phenomena like pulsars (fast spinning neutron stars), dark matter, the cosmic microwave background (signals left over from the universe’s birth) and, of course, FRBs.
• Radio astronomers today are much better off with telescopes that can even localise FRBs with arc-second precision, so that observations in other wavelengths could hunt for the FBR’s host galaxy.

CONCLUSION

• By connecting dots like these, astronomers try to unravel cosmic mysteries and better understand the universe, of which hardly a fraction is known.