Illustration by Karen Teramura, UH IfA
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Astronomers recently discovered that the 30 Ari system has four, not three, stars. The newly spotted star appears to the left of the planet in this artist's conception.

Illustration by Karen Teramura, UH IfA

Faraway Planet Gains a Fourth Sun

Discovery shows that quadruple-star systems may be more common than previously thought.

The Star Wars world of Tatooine has nothing on a distant planet now known to have a whopping four suns.  

Only the second known quadruple-star system found with a planet, 30 Ari hosts a gaseous super-Jupiter estimated to have ten times the mass of our solar system's largest planet. The behemoth orbits its primary star every 335 days but lies 23 times as distant from the newfound fourth star as Earth is from the sun, researchers reported March 4 in the Astronomical Journal.

Located 136 light-years away in the constellation Aries, 30 Ari was thought to be a triple-star system when its planet was discovered in 2009. The faint fourth star was found using new adaptive optics technologies attached to the Palomar Observatory telescope in California. The adaptive optics technique cancels out the blurring effect of Earth's atmosphere and provides crystal clear views of distant objects in space.

Multiple-star systems are more common than singletons like our sun. But the discovery of a fourth star in the already crowded 30 Ari suggests that systems with four or more stars may be more common across the Milky Way than astronomers had once believed.

The quadruple star system
This system is formed by two pair of stars (30 Ari A and B). One gas giant planet, in orange in this diagram, orbits one of the stars in 30 Ari B about once a year. New observations led by NASA identified another star in 30 Ari B, now the second quadruple star system known to host a planet.

30 Ari B

30 Ari A

Double-star system

Double-star system

Newfound star








Both double-star systems orbit a point in space between the two systems.

The orbits shown are approximations and are not as circular as they appear. Elements not to scale.

“About 4 percent of solar-type stars are in quadruple systems, which is up from previous estimates because observational techniques are steadily improving,” study co-author Andrei Tokovinin of the Cerro Tololo Inter-American Observatory in Chile said in a statement.

If we could visit this alien world and look up at its skies, the closest of the four stars would appear like a miniature version of the sun. Two superbright stars would be visible during daytime, and telescope users would be able to separate one of these stars into a pair: two stars orbiting each other.

See for Yourself

While 30 Ari is not bright enough to see with the unaided eye, with binoculars it is an easy target anywhere around the world.

View Images

A sky chart shows the position of 30 Ari within the Aries constellation, visible in the early evening this week in the low western sky. Venus serves as a convenient marker.

The system appears as a faint seventh-magnitude star among a sparse patch of sky in the constellation Aries the Ram.  

You'll find 30 Ari more easily by looking for the bright orange star Aldebaran, to its upper left, and a brilliant beacon, the planet Venus, directly below. The three form a distinct flattened triangular pattern with 30 Ari marking the peak.

Happy hunting!

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