Although undoubtedly rare, this is the second exoplanet discovered in a quadruple star system. The first, KIC 4862625, was discovered by a citizen science project that scours data from the Kepler space telescope to seek out exoplanetary transit signals. But the fact that two such systems have been discovered, when only a couple of thousand exoplanets have been discovered so far, hints that exoplanet formation can occur in some pretty unlikely places.
"Star systems come in myriad forms. There can be single stars, binary stars, triple stars, even quintuple star systems," said Lewis Roberts of JPL. "It's amazing the way nature puts these things together." Roberts is the lead author of the study to be published in the Astronomical Journal.
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Most stars in our galaxy are known to exist in multi-star systems and astronomers are currently trying to understand how they came to be this way. Were the stars gravitationally bound at birth inside their stellar nurseries? Or did they capture one another some time in their travels around the Milky Way? Recent unrelated research hints that multi-star systems may be born that way.
Now, with the increasing number of exoplanet discoveries in binary and multi-star systems, we are quickly realizing that many of our science fiction notions of far-off alien worlds are now actually modern science fact. One such world is Luke Skywalker's homeworld Tatooine from "Star Wars: A New Hope", where, at sunset, two stars of a binary pair dip low on the horizon.
But how would this multi-star system look from the vantage point of the exoplanet in 30 Ari? According to a NASA JPL news release, "the four parent stars would look like one small sun and two very bright stars that would be visible in daylight. One of those stars, if viewed with a large enough telescope, would be revealed to be a binary system, or two stars orbiting each other."
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In this research, another exoplanet in a triple-star system called HD 2638 is also detailed. In that system, where a third star has just been confirmed, the "hot-Jupiter" exoplanet has a roller coaster 3-day orbit around its star.
How multi-star systems affect the evolution of planets is of key interest to Roberts' team - these two multi-star systems play host to at least one massive planet, boosting evidence that planets inside multi-star systems can have their orbits dramatically modified by the crazy orbital dynamics such systems possess, although the newly-discovered star in 30 Ari does not seem to be impacting the orbit of its neighboring exoplanet.
These systems also appear to boost the mass of exoplanets. Only through the discovery of more examples such as 30 Ari and HD 2638 can we understand the driving physics of massive exoplanet evolution.