Massive Exoplanet Raised by Four Parent Stars

Growing up with two parents is hard enough, but four? Researchers discovered a massive exoplanet that was raised by four parent stars, shedding light on these types of complicated and largely unstudied solar systems.

Planets in our solar system orbit just one star - the Sun - but more distant planets called exoplanets can be reared in families with two or more stars. However, how exactly these multiple stars influence far-away planets remains to be seen.

This is only the second time ever a planet has been identified in a quadruple star system. The first, KIC 4862625, was discovered in 2013 by citizen scientists using public data from NASA's Kepler mission.

It should be noted that scientists already knew about this newfound four-star planetary system, called 30 Ari. But it was believed to harbor three stars, not four. That is, until a team at NASA's Jet Propulsion Laboratory (JPL) using the automated Robo-AO system at the Palomar Observatory in San Diego and the PALM-3000 adaptive optics system found the fourth star, situated at a distance of 23 astronomical units (AU) from the planet. (An astronomical unit is the distance between the Earth and the Sun).

In the case of 30 Ari, it is located 136 light-years away in the constellation Aries. The planet is a gas giant, with 10 times the mass of Jupiter, and it orbits its primary star every 335 days. This primary star has a "close neighbor" (that the planet does not orbit), and these two stars together orbit another pair of stars that is located about 1,670 AU away.

"Star systems come in myriad forms. There can be single stars, binary stars, triple stars, even quintuple star systems," Lewis Roberts of JPL, lead author of the study, said in a news release. "It's amazing the way nature puts these things together."

And though astronomers have now only discovered two four-star planetary systems, the findings suggest that there are many more out there.

"About four percent of solar-type stars are in quadruple systems, which is up from previous estimates because observational techniques are steadily improving," added co-author Andrei Tokovinin of the Cerro Tololo Inter-American Observatory in Chile.

Past evidence has suggested that parent stars can influence the orbit and even size of nearby planets, and this latest discovery helps provide some insight into this phenomenon. Roberts and his colleagues do not believe the newfound star in the 30 Ari system has had an influence on the planet's orbit, and they hope to conduct future investigations to better understand why that is.

The results were published in The Astronomical Journal.

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