Active galaxies boast massive black holes at their core that blast twin jets of radio waves out into space. Although most of these jets travel in opposing directions, astronomers have observed instances of the jets forming an X pattern in space. The phenomenon was seen, for instance, some 800 million light-years away in the galaxy PKS 2014-55.
The galaxy’s nucleus is surrounded by two boomerang-like arms stretching out into space, each measuring an estimated 2.5 million light-years.
Astronomers have proposed a number of theories to try and explain why the jets are taking on the unusual shape.
One theory suggested the jets would change direction over millions of years as a result of the black holes spinning.
Another theory suggested the jets are shaped by stellar material falling towards the black holes only to be deflected in new directions.
Astronomers in South Africa have now proposed the latter theory is the most likely explanation, revealing how the jets are “turning the corner” in space.
The finding was presented by the South African Radio Astronomy Observatory (SARAO) and accepted for publication in the journal Monthly Notices of the Royal Astronomical Society.
Observations of the galaxy PKS 2014-55 show ejected stellar material changes direction as it flows back towards its host galaxy.
The work was carried out by the SARAO together with the US National Radio Astronomy Observatory (NRAO) and the University of Pretoria and Rhodes University.
The observations were made possible by the MeerKAT radio observatory in South Africa.
The radio telescope consists of 64 radio dishes in the Karoo semi-desert in the Northern Cape province.
Combined, the antennas act like a telescope measuring 4.9 miles (8km) across.
MeerKAT allowed the astronomers to observe in high detail the youngest radio jets close to the galaxy’s central black hole.
The X or boomerang-shaped jets on either side of the black hole and galactic disk of stars are older jets of deflected material.
Astronomers divide galaxies into three main types: ellipticals, spirals and irregulars.
Our Milky Way is a spiral galaxy with four spindly arms coiling around a central massive black hole.
Elliptical galaxies are fairly round and featureless, are typically populated by older stars, and have a low rate of new star formation.
Irregular galaxies can take various shapes and forms, with some even taking on the form of a ring.
US space agency NASA said: “They are often chaotic in appearance, without a bulge or any trace of spiral arms.
“The different shapes and orientation of galaxies are a result of their history, which may have included interactions with other galaxies.”