London | Scientists have found evidence of icy comets orbiting a nearby Sun-like star, which could give a glimpse into how our solar system developed. Using data from the Atacama Large Millimetre Array (ALMA) in Chile, the researchers, led by the University of Cambridge in the UK, detected very low levels of carbon monoxide gas around the star, in amounts that are consistent with the comets in our own solar system.
The results are a first step in establishing the properties of comet clouds around Sun-like stars just after the time of their birth. Comets are essentially ‘dirty snowballs’ of ice and rock, sometimes with a tail of dust and evaporating ice trailing behind them, and are formed early in the development of stellar systems.
They are typically found in the outer reaches of our solar system, but become most clearly visible when they visit the inner regions. It is believed that when our solar system was first formed, the Earth was a rocky wasteland, similar to how Mars is today, and that as comets collided with the young planet, they brought many elements and compounds, including water, along with them.
The star in this study, HD 181327, has a mass about 30 per cent greater than the Sun and is located 160 light years away in the Painter constellation. The system is about 23 million years old, whereas our solar system is 4.6 billion years old. Young systems such as this one are very active, with comets and asteroids slamming into each other and into planets, said Sebastian Marino, a PhD student from Cambridge’s Institute of Astronomy.
The system has a similar ice composition to our own, so it’s a good one to study in order to learn what our solar system looked like early in its existence, Marino said. Using ALMA, the astronomers observed the star, which is surrounded by a ring of dust caused by the collisions of comets, asteroids and other bodies. It is likely that this star has planets in orbit around it, but they are impossible to detect using current telescopes, researchers said.
Assuming there are planets orbiting this star, they would likely have already formed, but the only way to see them would be through direct imaging, which at the moment can only be used for very large planets like Jupiter, said Luca Matra, also a PhD student at Cambridge’s Institute of Astronomy.
In order to detect the possible presence of comets, the researchers used ALMA to search for signatures of gas, since the same collisions which caused the dust ring to form should also cause the release of gas. Such gas has only been detected around a few stars, all substantially more massive than the Sun.
Using simulations to model the composition of the system, researchers were able to increase the signal to noise ratio in the ALMA data, and detect very low levels of carbon monoxide gas. The findings appear in the journal Monthly Notices of the Royal Astronomical Society.
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