This Newly Forming Planet Will Have Three Suns

A triple-star system has two disks of gas and dust that could form planets

illustration of GG Tau-A
An artist's impression of the triple-star system of GG Tau-A, which might have the right conditions for planet formation ESO/L. Calçada

Our sun is weird. It’s in the minority of star systems because it spins through space alone — it has no partner — while most stars dance in binary systems. In fact, many planets may enjoy the light of twin suns. Until this past decade, most researchers thought that binaries were unlikely places for planets to form, but a better understanding of the forces and history of these systems led them to revise that assessment.

Still, a planet with three suns seemed unlikely. But new observations indicate that a triple-star system with a planet is not just science fiction.

The constellation Taurus harbors a star triad called GG Tau A that includes a single star surrounded by a disk of gas and dust and circled by two other stars. The whole system is adorned by an outer ring. Now, scientists suspect that both the inner and outer rings might have the beginnings of young planets; in the outer ring, there is a condensation that may be an already formed planet. 

The team, based at the University of Bordeaux and France’s National Center for Scientific Research, reported the findings in Nature.

“If all goes well, in a few million years we may have a circumtriple planet and a circumstellar planet in the same system,” astronomer William Welsh of San Diego State University, who was not involved in new study, told Nadia Drake for her National Geographic blog. “This system would be off the charts in terms of the coolness factor.”

The finding is cool beyond imagining constant eclipses, weird combinations of sunrises and sunsets. Researchers were fairly convinced that three stars including a close binary would create a system too turbulent for planets to form. Drake explains how this system bucked the stereotype:

What [Anne] Dutrey and her colleagues found is that there’s a streamer of gas connecting the system’s outer ring with the inner disk, kind of like a lifeline. Material appears to be flowing in from the outer reservoir and replenishing the disk around that single star, keeping it alive long enough to (maybe) grow planets.

Science fiction has long been inspired by the idea of gazing at multiple suns. Tatooine’s binary in the Star Wars universe is just the most commonly known example. There are a wealth of stories that have explored the implications of complex star systems. 

Of course, even a triple-star system has nothing on the fictional world of Isaac Asimov’s "Nightfall," where six stars keep the entire planet in daylight, except for a prolonged eclipse every 2049 years. This world goes mad without a sun shining:

With the slow fascination of fear, he lifted himself on one arm and turned his eyes toward the blood-curdling blackness of the window. Through it shone the Stars! 

Not Earth's feeble thirty-six hundred Stars visible to the eye; Lagash was in the center of a giant cluster. Thirty thousand mighty suns shone down in a soul-searing splendor that was more frighteningly cold in its awful indifference than the bitter wind that shivered across the cold, horribly bleak world. 

But back in reality: The new observations means that the search for extraterrestrial planets just expanded to include triple-star systems. Who knows, someday we may ask the inhabitants of another planet what it's like to live under the light of multiple suns.

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