Galway astronomer in global team that detected giant collision in space

21 Oct 2021

Artist’s impression of a giant impact releasing gas from the atmosphere of a Venus-like planet. Image: Mark A Garlick

Researchers at NUI Galway, MIT and Cambridge used the ALMA telescope to provide a ‘window to the composition of young planets’.

An astronomer from NUI Galway is part of an international team that for the first time found evidence of a planet’s atmosphere being stripped away by a giant collision in a nearby star system.

At just 95 light years from Earth, the young star named HD 172555 was witness to an impact between two newly formed planets that are estimated to be about the size of Earth.

Using the Atacama Large Millimeter/submillimeter Array (ALMA) radio telescope in Chile, researchers from NUI Galway, MIT and Cambridge University studied the collision and unexpectedly detected a ring of carbon monoxide gas in the dust produced.

“This, for the first time, indicates that impacts can release large amounts of gas as well as dust, and that this gas can survive long enough to be detected,” said Dr Luca Matrà, an adviser for the study and lecturer at NUI Galway’s Centre for Astronomy.

Based on the amount of gas detected, the team was able to estimate that the size of the impact was likely massive and dated it to around 200,000 years ago. “This has the potential to revolutionise our understanding and observability of giant impacts,” Matrà added.

‘Window to the composition of planets’

Findings of the study were published yesterday (20 October) in the journal Nature. It may solve years of mystery around the unusual composition of dust observed by scientists in the HD 172555 region – indicating the aftermath of a planetary impact like the one that led to the formation of the moon.

The ALMA observatory used for the study consists of 66 radio telescopes working in unison. Ireland gained access to it after joining the European Southern Observatory (ESO) in 2018. It was used in a study published in July to understand how moons are formed.

Matrà said that the amount of gas discovered in this latest research is 10 to 20pc of the mass of Venus’ atmosphere, which “goes on to show the incredible sensitivity of the observations”.

“This puts forward gas observations as a viable detection method of terrestrial planet-forming collisions, and as a window to the composition of young planets,” he said.

Lead author Tajana Schneiderman of MIT said that this the first time scientists have detected the phenomenon of protoplanetary atmosphere being stripped away in a giant impact.

“Everyone is interested in observing a giant impact because we expect them to be common, but we don’t have evidence in a lot of systems for it. Now we have additional insight into these dynamics.”

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Vish Gain is a journalist with Silicon Republic