THIS image illustrates how the X-shape is formed and how a new, young pair of jets have just started up near the super-massive black hole at the heart of the galaxy (inset). Picture: UP
THIS image illustrates how the X-shape is formed and how a new, young pair of jets have just started up near the super-massive black hole at the heart of the galaxy (inset). Picture: UP

SA scientists help solve the mystery of galaxies that spew X-shaped radio waves

By Mwangi Githathu Time of article published May 11, 2020

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Cape Town - South African scientists using the MeerKAT telescope have solved a galactic puzzle that has perplexed astronomers for years, and their discovery is set to be published in the prestigious Monthly Notices of the Royal Astronomical Society journal.

Using the high-quality imaging provided by the MeerKAT telescope, inaugurated in 2018, scientists from the South African Radio Astronomy Observatory (SARAO), solved a longstanding puzzle in “X”-shaped radio galaxies by observing a galaxy called PKS 2014-55 that’s situated 800 million light years away from Earth.

The feat was achieved by the astronomers from SARAO, which operates MeerKAT, together with colleagues from the (US) National Radio Astronomy Observatory (NRAO), the University of Pretoria, and Rhodes University.

Astronomers had been puzzling over some galaxies that spew out X-shaped jets of radio waves from the black holes that lurk at their centres.

THE galaxy PKS 2014-55, 800 million light-years from Earth, is classified as “X-shaped” because of its appearance in previous comparatively blurry images. The detail in this radio image obtained with the MeerKAT telescope shows its shape is best described as a “double boomerang”. Picture: NR AO/AUI/NSF; SARAO; DES

A post-doctoral fellow at the University of Pretoria and second author of the paper, Dr Kshitij Thorat, said: “This galaxy is one of many with similar X-shaped morphologies carefully chosen to be studied in a MeerKAT observation campaign aimed at solving the mystery of X-shaped radio galaxies.”

Thorat said: “While other telescopes around the world hinted at this object’s unusual morphology, it took the crystal-clear image quality of MeerKAT to reveal the underlying physical causes.

“As a bonus, we have produced one of the most beautiful radio images I have ever seen.”

Dr Kshitij Thorat, second author of the paper, and post-doctoral fellow at the University of Pretoria. Picture: Supplied

Astronomers had considered that X-galaxies might be created by changes in a black hole’s spin direction or by two black holes working as a team. MeerKAT’s clear view of PKS 2014-55, however, supports the double-boomerang model.

Professor Roger Deane, who leads the UP astronomy group and is a co-author of the study, said: “We’ve made a concerted effort over the past two years to build a team able to make important scientific discoveries with cutting-edge radio telescopes. The rapid growth we’ve seen is gratifying and encouraging, particularly with the exquisite images the team is making with South Africa’s MeerKAT telescope, a precursor to the Square Kilometre Array.”

The MeerKAT telescope array consists of 64 radio dishes located in the Karoo semi-desert in the Northern Cape province of South Africa.

@MwangiGithahu

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Cape Argus

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