Astronomers have spied on three exoplanet systems born around a single binary star. Yes, not just one or two, three planetary systems were found around a sun-like star.
SVS 13 is a binary star system 980 light-years away, and the complex dust structure around it explains how planetary systems were born in this amazing environment. Since most stars are bound together in multiple star systems, this has implications for our understanding of planet formation and evolution.
"Our results have revealed that each star has a disk of gas and dust around it, and in addition, a larger disk is formed around the two stars," said astronomer Ana Karla DÃaz-RodrÃguez of the Institute of Astrophysics of Andalusia (IAA-CSIC) in Spain and the ALMA Regional Center at the University of Manchester, UK.
"These outer disks show a spiral structure that feeds material into each disk, and in all of which planetary systems could form in the future. This is clear evidence of the existence of disks around both stars and the existence of disks common in binary systems," he continued.
A star is born from a dense knot in a cloud of molecular gas floating in space. Under the right conditions, one of these nodes will collapse under its own gravity and begin to spin. As it rotates, the material around it flattens into a disk that rolls into a star and feeds its growth.
When a star reaches the end of its formation, whatever remains becomes a protoplanetary disk. All the remaining dust and gas is jostled, and eventually gathers in sizable clumps that form planets, asteroids, comets, moons, dwarf planets, and everything else we can find in a planetary system.
We know this happens around single stars easily. Our own Solar System is proof that it can happen, and most of the exoplanets confirmed to date have been found orbiting single stars.
Quoted from Science Alert, it is thought that multiple star systems, which create more gravitationally complicated environments, may be more hostile to planet-forming processes.
SVS 13 is relatively close. He is in a star-forming cloud called the Perseus molecular cloud, and is very young. It consists of two stars with nearly the same combined mass as the Sun, locked in a very tight orbit. Their distance is "only" about 90 astronomical units (Pluto is about 40 astronomical units from the Sun).
To learn more about the space around these binary protostars, as well as the stars themselves, DÃaz-RodrÃguez and his team studied 30 years of observations from the Very Large Array of Radio Astronomy's National Observatory. They also made new observations with the Atacama Large Millimeter/submillimeter Array known as ALMA.
This allowed the team to reconstruct the binary orbits, and determine the mass of the star, the orientation of the system, and the size and mass of the disk. They found two small disks, one with a dust radius of 12 astronomical units, and the other with a dust radius of 9 astronomical units, both with a gas radius of 30 astronomical units.
The large spiral circumbinary disk, which covers both stars, has spiral arms that extend 500 astronomical units.
"At the IAA we started studying this system twenty-five years ago. We were surprised when we discovered that SVS 13 is a radio binary, because only one star is visible optically," said astronomer Guillem Anglada of IAA-CSIC.
"It's very strange to find a pair of twin stars where one seems to be evolving much faster than the other. We designed some experiments to get more details and to find out if in such a case one of the stars could form a planet. Now we have seen that both the star is very young, and both can form planets," he said.
There's more reason to be interested in the system than resolving the debate around the age of the two stars. Previous studies of this system identified molecules in the dust and gas around SVS 13, including complex organic molecules that are precursors to the building blocks of life.
"This means that when the planets started to form around these two Suns, the building blocks of life would be there," said DÃaz-RodrÃguez.
We're definitely not old enough to see the process unfold. But knowing that the molecules are there can help us unravel the mysteries of our existence in the Universe.