Astronomers find new clue about mysterious radio flashes in space

Subject: Science and technology

Section: Space technology

Context:

Fleeting flurries of radio waves, called fast radio bursts (FRBs) reach earth from faraway galaxies, emitting as much energy in a millisecond as the sun does over weeks.

About FRBs:

The precise origin of FRBs and why they appear in such short, sharp bursts is not known yet.
Although, 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.

What did the astronomers find?

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.
Using these observed features, the researchers modelled the variations as being the result of a wind from a massive binary companion star.
The wind of a star is a rapid stream of ejected material.
In other words, the magnetic reversal likely happened when the radio signals passed through a turbulent, magnetised screen of plasma in the binary stellar system.

What do the findings mean?

This conclusion ties in with an older discovery of a strikingly similar binary system in the Milky Way galaxy, including the magnetic field reversal.
The study gives one of the most convincing pieces of evidence that this source could be in a binary system.
It is possible that all repeating FRBs could be in binariesbut differ in their local conditions, like the orbital period or the orbital inclination.
The radio telescopes used in the research include:
- The Very Large Array and Deep Synoptic Array-110 in the U.S.,
- China’s Five-hundred-meter Aperture Spherical radio Telescope,
- Australian Square Kilometre Array Pathfinder,
- India’s upgraded Giant Metre-wave Radio Telescope,
- Germany’s Effelsberg Radioteleskop,
- South Africa’s MeerKAT, and
- Low-Frequency Array in the Netherlands.

Why do radio telescopes matter?

The long wavelengths of Radio spectrum allow radio waves to traverse intergalactic space without interruption, making them an ideal tool to identify radio emissions from faraway heat sources.
In 1933 the radio engineer Karl Jansky’s investigations led him to the accidental discovery of radio waves coming from the centre of the Milky Way galaxy.
Due to Jansky’s pioneering findings and further research, 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.
The present telescopes can even localise FRBs with arc-second precision, so that observations in other wavelengths could hunt for the FBR’s host galaxy.
So when a radio telescope spots an FRB, astronomers try to determine its dispersion value: the extent to which the FRB is stretched out when it reaches earth. From this, it is possible to calculate the distance to the FRB’s source.
By connecting dots like these, astronomers try to unravel cosmic mysteries and better understand the universe.

Pulsars:

Pulsars are rotating neutron stars observed to have pulses of radiation at very regular intervals that typically range from milliseconds to seconds.
Pulsars have very strong magnetic fields which funnel jets of particles out along the two magnetic poles. These accelerated particles produce very powerful beams of light.

Giant Meter-wave Radio Telescope (GMRT)- India:

GMRT is an array of thirty fully steerable parabolic radio telescopes of 45 meter diameter.
- Operated by the National Center for Radio Astrophysics of the Tata Institute of Fundamental Research (NCRA-TIFR).
GMRT is an indigenous project. Its design is based on the `SMART’ concept – for Stretch Mesh Attached to Rope Trusses.
It functions at the meter wavelength part of the radio spectrum because man-made radio interference is considerably lower in this part of the spectrum in India and there are many outstanding astrophysics problems which are best studied at metre wavelengths.
Location– Pune meets several important criteria such as low man-made radio noise, availability of good communication, vicinity of industrial, educational and other infrastructure and,a geographical latitude sufficiently north of the geomagnetic equator in order to have a reasonably quiet ionosphere and yet be able to observe a good part of the southern sky as well.
GMRT is presently the world’s largest radio telescope operating at a meter wavelength.