There are many planets around stars the size of our sun, and about every second one is a double star. This makes them obvious targets for astronomers looking for extraterrestrial life forms.

The latest study from Denmark and the University of Michigan shows that planetary systems form very differently around binary stars, which are two stars that are gravitationally bound together than they do around single stars like the sun.

Co-author Edwin Bergin, a professor and chair of the University of Michigan’s Department of Astronomy, said the researchers began studying NGC 1333-IRAS2A in an effort to better understand how stars and planets form.

“We were trying to peer as close as we could to the most luminous star in the binary—the primary star—and observe the beginnings of planetary system formation, and we got it, but in a different way,” Bergin explained. “The result that we have has something to do with how planetary systems form, and it’s that the binary star system can influence planetary formation tremendously.”

Jes Kristian Jrgensen, a professor of astrophysics and planetary science at the University of Copenhagen’s Niels Bohr Institute and the study’s primary investigator, believes the findings will aid in the search for extraterrestrial life.

“The result is exciting since the search for extraterrestrial life will be equipped with several new, extremely powerful instruments within the coming years,” he added. “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.”

The findings of the project, which also included Taiwanese astronomers, were reported in Nature.

The team used time on the ALMA telescopes in Chile to look at the NGC 1333-IRAS2A binary star system in the Perseus molecular cloud. In astronomical terms, the distance between Earth and the binary star is around 1,000 light-years, which is a relatively modest distance. It is a fairly young star, having formed 10,000 years ago. The binary system’s two stars are 200 astronomical units apart. The distance between Earth and the sun is measured in AUs. In comparison, Neptune, the solar system’s furthest planet, is 30 AU from the sun.

The gas and dust that make up the disc are all around the two stars. Some of the stuff is going away from us, while others are moving closer. The observations can only give researchers a snapshot of NGC 1333-IRAS2A at a certain stage in its history. The observations have been supplemented by computer simulations that go both backward and forward in time.

“The observations allow us to zoom in on the stars and study how dust and gas move toward the disk. The simulations will tell us which physics is at play and how the stars have evolved up till the snapshot we observe and their future evolution,” Rajika Kuruwita, a postdoctoral researcher at the Niels Bohr Institute, explained.

The circulation of gas and dust, in particular, does not follow a consistent pattern. The movement gets extremely strong at some moments in time—typically for 10 to 100 years every thousand years. The binary star brightens ten to one hundred times before returning to its original state.

The binary star’s duality is probably responsible for the cyclic pattern. The two stars are encircling each other, and their combined gravity will affect the surrounding gas and dust disc at regular intervals, causing massive amounts of material to descend toward the star.

“The falling material will trigger significant heating. The heat will make the star much brighter than usual,” Kuruwita predicted. 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.”

Planets haven’t formed yet because the star system is still young. The team intends to gain more observing time so that they can study planetary system formation. According to Jrgensen, the researchers only have five hours of ALMA observation time and want to receive 100 hours for a new project. Astronomers would also like to study comets, which contain a lot of ice and chemical substances.

ALMA is made up of 66 telescopes that work together to create a single instrument. This enables significantly higher resolution than could be achieved by a single telescope. ALMA will allow scientists to explore how comet impacts could introduce organic molecules to barren planets, as it allows them to see complex organic molecules.

“The binary is clearly influencing the evolution of the disk of material around the main system. And that suggests, since most stars form as binaries, that the binary will influence the ultimate composition of planets that are born,” Bergin added. “Is it any different if you were born as a single star? We don’t know that. We have observed that most stars are born in binaries but many of these binaries drift apart over time.

“So how important is this for the formation of planetary systems and the formation of habitable worlds? Another way of saying this in the ‘Star Wars’ parlance is how many Tatooines are out there? We don’t know, but what we now know is that, hey, this matters.”

Image Credit: Getty

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