An international team, including an astronomer from NUI Galway, have detected evidence of a giant impact that occurred in a nearby star system.
The findings, based on the research by NUI Galway, Massachusetts Institute of Technology (MIT) and Cambridge University have been published in the leading international journal Nature.
It is the first discovery of a planet’s atmosphere being stripped by a giant impact.
The star that gave astronomers this rare glimpse into planetary formation is HD172555, located 95 light years away from Earth.
This star has been an object of interest to astronomers due to the large amount of dust orbiting within the terrestrial planet region — where rocky planets, such as Earth, are often formed.
Terrestrial planets are formed over the first tens of millions of years of a star’s lifetime. Scientists have theorised that in the latest stages of formation, planets grow through giant impacts with each other.
These giant collisions produce planets, satellite objects like the moon, as well as dust and debris. As The dust and debris produced can then be observed by telescopes on Earth.
Using the Atacama Large Millimeter/submillimeter Array observatory (ALMA), located in Chile, the team observed a carbon monoxide ring in the dust produced by the impact.
“This 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, advisor for the study and Lecturer in the Centre for Astronomy, School of Physics in NUI Galway.
“This has the potential to revolutionise our understanding and observability of giant impacts,” he added.
Based on the amount of gas present, the impact is estimated to have occurred about 200,000 years ago between two young planets similar in size to Earth.
Dr Matrà said that the amount of gas discovered is 10-20 per cent of the mass of Venus’ atmosphere, and that this amount shows the 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.
The star system is estimated to be about 23 million years old — making it younger than the solar system which is about 4.6 billion years old. Based on prediction models, HD172555 is within the age range where planet formation from giant impacts is expected to happen.
Tajana Schneiderman, lead author of the study, and a graduate student in MIT’s Department of Earth, Atmospheric, and Planetary Sciences, said: “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.”
