Planets Around Two Stars Probably Didn’t Form Like Those In Our Solar System

Observations of a young binary star system have led astronomers to new insights into how planets might form. In a system with two or more stars, planetary disks are cyclically sloshed about by the combined effects of the stars, and these dramatic changes are likely to influence the formation of worlds around these stars† Given how almost half of all Sun-sized stars are in pairs, understanding these systems is very important.

The starting point of the work – published in the journal Nature – are observations of binary star system NGC 1333-IRAS2A. The two stars are surrounded by a disk of gas and dust. Researchers from Denmark, Taiwan, and the US used simulations to study both the past and the future of this system.

The computer model showed that, based on the snapshot in time that is the recent observations, the movement in the disk is not following a continuous pattern. It appears that for short periods, lasting a few decades every few thousands of years, the binary stars become up to 100 times brighter before fading back to their baseline.

“The falling material will trigger a significant heating. The heat will make the star much brighter than usual,” co-author Dr Rajika L. Kuruwita, from the Niels Bohr Institute, said in a statement† “These bursts will tear the gas and dust disc apart. While the disc will build up again, the bursts may still influence the structure of the later planetary system.”

The observations were conducted with the Atacama Large Millimeter/submillimeter Array, which has the ability to see the emissions from interesting chemicals forming around stars. While the binary system has no planets around it yet, the observatory can study what substances are currently present and the team can speculate on what might form in the future.

“The heating caused by the bursts will trigger evaporation of dust grains and the ice surrounding them. This may alter the chemical composition of the material from which planets are formed,” added Professor Jes Kristian Jørgensen, Niels Bohr Institute, University of Copenhagen, heading the project.

New observatories, from JWST to the Square Kilometer Array and Extremely Large Telescope, will probe systems like this even further and provide new insights into if and how planets around binary stars could host life.

“The result is exciting since the search for extraterrestrial life will be equipped with several new, extremely powerful instruments within the coming years,” Professor Jørgensen explained. “This enhances the significance of understanding how planets are formed around different types of stars. Such results may pinpoint places which would be especially interesting to probe for the existence of life.”

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