Cosmic gift: Rare ribbon-wrapped galaxy found by ASKAP telescope

A gift-wrapped galaxy has been found by the CSIRO’s ASKAP radio telescope. The rare galaxy which appears to be wrapped in a cosmic ribbon, is 56 million light-years from Earth.

NGC 4632 is a spiral galaxy in the Virgo constellation. In 2022, astronomers first noticed an anomalous gas structure around the galaxy, but new stunning images from ASKAP have revealed this galaxy is surrounded by a “ribbon.”

The findings are published in Monthly Notices of the Royal Astronomical Society.

Four radio telescope dishes under milky way stars
CSIRO ASKAP core antennas under the Milky Way. Credit: CSIRO/A. Cherney.

Astronomers believe they are looking at a rare “polar ring galaxy.” These have a ring or disk of material perpendicular to the orientation of the galaxy itself. They are among the most striking and mysterious objects in the universe.

The gaseous ring around NGC 4632 is only observable from Earth in the radio wavelengths.

“The findings suggest that 1–3% of nearby galaxies may have gaseous polar rings, which is much higher than suggested by optical telescopes,” says co-author Dr Nathan Deg from Queen’s University Canada. “Polar ring galaxies might be more common than previously thought.”

“While this is not the first time astronomers have observed polar ring galaxies, NGC 4632 is the first observed with ASKAP and there may be many more to come,” Deg says.

The galaxy was found as part of ASKAP’s Widefield ASKAP L-band Legacy All-sky Blind surveY (WALLABY) which is mapping half of the sky over the southern hemisphere.

“NGC 4632 is one of two polar ring galaxies we’ve identified from 600 galaxies that were mapped in our first small WALLABY survey,” says CSIRO’s Professor Bärbel Koribalski. “Using ASKAP over coming years we expect to reveal more than 200,000 hydrogen-rich galaxies, among them many more unusual galaxies like these ones with polar rings.”

The cause of polar rings around galaxies remains unclear.

They may be material sheared off a neighbouring galaxy. Alternatively, they could be hydrogen gas that has flowed along cosmic filaments – strands of dark matter theorised to exist around galaxies – and accreted due to gravity.

As such, studying polar ring galaxies may provide further clues as to the nature of dark matter as well as the history and evolution of galaxies.

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