Now, astronomers have found 30 exomoons, or comets located outside our solar system, orbiting the sun-like star Beta Pictoris, which makes it even more intriguing.
The star of Beta Pictoris was discovered nearly 40 years ago. It is surrounded by a debris disk made of gas and dust, which has already given birth to two young planets orbiting the star. It provides researchers with a rare opportunity to see a planetary system in the making. While our solar system is 4.5 billion years old, Beta Pictoris is only 20 million years old — astronomically young.
Scientists were able to detect some comets grazing the star as early as 1987, making them the first comets ever observed around a star beside our sun.
An international research team observed the Beta Pictoris system for 156 days using NASA’s Transiting Exoplanet Reconnaissance Satellite, or TESS, mission.
In addition to discovering 30 exocomets, the researchers were also able to determine the size of cometary cores – the icy “dirty snowball” that makes up the comet’s core. When comets pass close to the star, the star’s heat causes their ice to sublimate, creating long, flowing tails that can extend behind the comets.
The cores of the outer continents are between 1.8 and 8.7 miles (3 and 14 kilometers) in diameter, similar to comets in our Solar System. This is the first time that astronomers have measured the size distribution of comets in another planetary system.
Comets in Beta Pictoris “graze the star almost every day,” study lead author Alain Lecavelier des Etangs, a CNRS researcher at the Astrophysical Institute in Paris, said in a statement.
Just like the comets that astronomers study in our solar system, exo- comets were formed by collisions with other objects.
“This illustrates the importance of interactions, collisions and material exchange between planets and small bodies such as asteroids or comets in the early life stage of a planetary system,” said Lecavilliers de Etang.
It is possible that some of the water on Earth originated from comets and their icy content, so scientists are interested to know how comets affect exoplanets as well.
“We cannot confirm that the observed comets are likely to transfer material such as water to planets orbiting Beta Pictoris, but our observations show that collisions are very common, and thus suggest that temperate planets can be enriched in material trapped in the frozen ice that comets capture when ( Comets) are far from the star and later collide with the planets.
While there are many similarities between the outer comets of Beta Pictoris and the comets of our own solar system, how similar and different they are “remains to be determined,” Lecavelier des Etangs said.
External comets could help shed light on the origin and evolution of comets in general, and future observations of the planetary system using Hubble and the James Webb Space Telescope could reveal more details about them.
“The question of the formation of these comets is still open,” he said.
The researchers want to determine what material sublimates, or transforms, from a solid to a gas, as the outer comets approach the star Beta Pictoris. It could be water ice, carbon monoxide, or something else entirely.
The system has a unique combination of three factors that keep astronomers coming back: it’s young and close and telescopes have the perfect view of it from Earth.
“Nature has provided us with this amazing goal,” said Lecavelier des Etangs. “Many questions remain open. I’m sure Beta Pictoris will keep us busy for decades to come!”