The two suns that adorn the sky of Tatooine, Luke Skywalker’s home world, offer one of the most iconic backdrops in the whole Star Wars franchise. But binary star systems are not only a setting in science fiction, they are also an extremely common stellar configuration in space; in fact, nearly half of Sun-size stars in our galaxy have a companion.
The ubiquity of this so-called “binarity” in stars raises intriguing questions about their potential to host alien life, and how their habitability might be different from single star systems like our own solar neighborhood.
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Now, scientists led by Jes Kristian Jørgensen, an astrophysicist at the University of Copenhagen’s Niels Bohr Institute, have shed new light on these questions by examining the birth of a binary star system called NGC 1333-IRAS2A, which is located about 1,000 light years from Earth.
By combining high-resolution observations with sophisticated simulations, the team discovered that “binarity and multiplicity in general strongly affect the properties of the emerging stars, as well as the physical and chemical structures of the protoplanetary disks and therefore potentially any emerging planetary systems,” according to a study published on Monday in Nature.
“The result is exciting since the search for extraterrestrial life will be equipped with several new, extremely powerful instruments within the coming years.” said Jørgensen in a statement. “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.”
Jørgensen and his colleagues were able to observe new details about the dynamics and chemical composition of NGC 1333-IRAS2A with the help of the Atacama Large Millimeter/submillimeter Array (ALMA) in Chile, which is one of the most powerful observatories on Earth. The team peered at the nascent system with ALMA for two nights in July 2019, which enabled them to capture “a snapshot in time of the formation of a binary system,” according to the study.
Star systems are born from collapsing clouds of gas and dust known as protoplanetary disks, which can eventually evolve into planetary systems. In binary systems, the disks of the two stars interact with each other in complex and sometimes explosive ways that are bound to shape the properties of any planets that emerge from them.
For instance, the ALMA observations of NGC 1333-IRAS2A show that the interactions between the two disks occasionally cause more gas and dust to fall toward a star in the system, causing a massive burst of heat and energy that can make the system ten to one hundred times brighter for periods of several decades. These outbursts sculpt the natal gas clouds in very different ways compared to the more stable formations of single star systems, which could influence their chemical makeup.
“The heating caused by the bursts will trigger evaporation of dust grains and the ice surrounding them,” Jørgensen explained. “This may alter the chemical composition of the material from which planets are formed.”
“The wavelengths covered by ALMA allow us to see quite complex organic molecules, so molecules with 9-12 atoms and containing carbon,” he added. “Such molecules can be building blocks for more complex molecules which are key to life as we know it.”
While the new study confirms that binary star systems experience their own distinct evolutionary processes, it will take more observations and simulations to understand exactly how these differences impact their potential to host alien life. To that end, Jørgensen and his colleagues plan to continue studying NGC 1333-IRAS2A, and other systems like it, with next-generation observatories such as the recently launched James Webb Space Telescope.
“As there is some evidence that planet-formation has already started during the deeply embedded stages studied here,” concluded the team in the study, “these effects may all be important components for determining the physical and chemical characteristics of the emerging planets.”
