Astronomers using the MeerKAT telescope on the South African Radio Astronomy Observatory in Cape Town, South Africa, have solved a longstanding mystery of X-shaped radio galaxies.
Many galaxies far more active than the Milky Way have substantial duo jets of radio waves extending some distance into intergalactic space.
Normally those move in opposite directions, coming from a big black hole in the center of the galaxy. However, some are more complicated and seem to have four jets forming an 'X' at the sky.
Zooming in on a cosmic giant
The researchers took detailed photographs of galaxy PKS 2014-55 last year, as part of the Evolutionary Map of the Universe challenge led by astrophysicist Ray Norris. They used CSIRO's Australian Square Kilometre Array Pathfinder (ASKAP) telescope in Western Australia, which just finished its first set of pilot astronomical surveys.
Thanks to its innovative "radio cameras", ASKAP can rapidly map very big regions of the sky to catalog thousands and thousands of items emitting radio waves, from close by supernova remnants to distant galaxies.
The outstanding X-form of PKS 2014-55 is made up of two pairs of large lobes consisting of warm jets of electrons. These jets spurt outwards from a supermassive black hole at the galaxy's heart.
The lobes emit electromagnetic radiation in the shape of radio waves, which can handiest be detected through radio telescopes like ASKAP. Humans can not see radio waves. But if everyone could, from Earth, PKS 2014-55 could look about the same size as the Moon.
What makes a radio galaxy?
Typically, radio galaxies have only one pair of lobes. One is a "jet" and the other a "counter-jet."
These jets enlarge into the surrounding space at nearly the speed of light. They initially circulate in a straight line, but twist and bend into many marvelous shapes as they come upon their surroundings.
Galaxy PKS 2014-55's giant X-shape, with pairs of lobes rising at unique angles, is highly unusual.
What makes the lobes?
Nearly all big galaxies have a supermassive black hole at their core. In a lively galaxy, powerful jets of charged particles can emerge from the place across the supermassive black hole.
Astronomers believe those are emitted from close to the poles of the black hole, that is why there are of them, and they usually point in opposite directions.
When the black hole's activity stops, the jets stop developing, and the cloth in them flows returned towards the center. Thus, what we see as one lobe of a radio galaxy is made up of each a jet spurting out, and the backflow material.
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A mystery solved
In the past, there have been two primary theories for why PKS 2014-55 has pairs of lobes.
The first theory had two big energetic black holes on the galaxy's center, each emitting two powerful jets.
The second concept suggested the supermassive black hollow had passed through a spin-flip. This is when a rotating black hollow's spin axis has a sudden shift in orientation, resulting in a second pair of jets at a one of a kind perspective from the primary pair.
But the current observations from the South African MeerKAT telescope strongly suggest a third possibility: that the two large lobes are the fast-changing particles zooming out from the black hole while the two smaller lobes are the backflow looping round to fall back in.
The MeerKAT group carried out high-resolution images ten instances more touchy than our ASKAP pilot observations conducted here in Australia last year.
