In our solar system, the planets orbit just one star – the Sun. That makes understanding how our solar system works relatively simple. Other systems, though, a built on multiple stars, which scientists find much more interesting. Case in point, a couple of new discoveries by NASA: A system with three parent stars, and the second planet ever found orbiting a quadruple-star system.
“Star systems come in myriad forms. There can be single stars, binary stars, triple stars, even quintuple star systems,” said Lewis Roberts of JPL, lead author of the new findings appearing in the journal Astronomical Journal. “It’s amazing the way nature puts these things together.”
The new four-star system, known as 30 Ari, isn’t “new” in the strictest sense of the word – the system (and its planet) have been known to scientists, but until now they were only aware of three of its stars. Identifying the fourth, combined with an orbiting exoplanet, marks only the second time such a phenomenon has been observed by science.
30 Ari’s planet is huge – 10 times the mass of Jupiter. The primary star has a relatively close partner star, though the planet orbits only the primary, circling every 355 days. The primary pair, in turn, is entangled in orbit with another pair of stars 1,670 astronomical units (the distance between Earth and the Sun) away.
The discovery of 30 Ari’s fourth star also revealed something strange – though it’s only 23 astronomical units away from the exoplanet, it appears to have no effect on its orbit. Scientists aren’t yet sure why this is, but the effect of multiple star systems on young planets is the objective of Roberts’ research.
In the other, three-star system, the planet is a “hot Jupiter” that orbits its parent star much more closely, completing the journey every three days. Scientists have long-known of the primary’s stellar dance partner, another star orbiting 44,000 astronomical units away (the astronomers note this is unusually far apart for companion stars). The newly discovered third star, however, orbits the primary at just 28 astronomical units. That’s close enough, the researchers believe, to have influenced the planet’s development and orbit.
“This result strengthens the connection between multiple star systems and massive planets,” said Roberts.