Skip to main content

This strange planet has three suns and orbits at a funky angle

This illustration shows the planet KOI-5Ab transiting across the face of a Sun-like star, which is part of a triple-star system located 1,800 light-years away in the Cygnus constellation.
This illustration shows the planet KOI-5Ab transiting across the face of a Sun-like star, which is part of a triple-star system located 1,800 light-years away in the Cygnus constellation. Caltech/R. Hurt (Infrared Processing and Analysis Center, or IPAC)

The oddities in our universe are many, and new research has thrown light on one such strange star system discovered more than a decade ago. Researchers have found a planet with three suns and an unusual kink in its orbit.

Planet KOI-5Ab was discovered all the way back in 2009, as just the second candidate discovered by NASA’s then-new Kepler mission. But no one paid much attention to this particular world as Kepler continued to discover new and exciting planets.

But there’s some value in looking back into the past for things that others have overlooked, as the team from NASA’s Exoplanet Science Institute discovered. Chief scientist David Ciardi poked back through the available data on KOI-5Ab from various different telescopes and discovered that it was well worth a second look.

“KOI-5Ab got abandoned because it was complicated, and we had thousands of candidates,” said Ciardi in a statement. “There were easier pickings than KOI-5Ab, and we were learning something new from Kepler every day, so that KOI-5 was mostly forgotten.”

KOI-5Ab’s most notable feature is that it is part of a triple star system, meaning it orbits a star that is in an orbital pattern with two other stars. The elaborate dance of the three stars and the planet is a rare thing to find already, and this system is even more unusual because the planet’s orbit is tilted at an angle.

Diagram of the orbits of the KOI-5 star system
The KOI-5 star system consists of three stars, labeled A, B, and C, in this diagram. Stars A and B orbit each other every 30 years. Star C orbits stars A and B every 400 years. The system hosts one known planet, called KOI-5Ab, which was discovered and characterized using data from NASA’s Kepler and Transiting Exoplanet Survey Satellite missions, as well as ground-based telescopes. KOI-5Ab is about half the mass of Saturn and orbits Star A roughly every five days. Its orbit is tilted 50 degrees relative to the plane of stars A and B. Astronomers suspect that this misaligned orbit was caused by Star B, which gravitationally kicked the planet during its development, skewing its orbit and causing it to migrate inward. Caltech/R. Hurt (Infrared Processing and Analysis Center, or IPAC)

“We don’t know of many planets that exist in triple-star systems, and this one is extra special because its orbit is skewed,” said Ciardi. “We still have a lot of questions about how and when planets can form in multiple-star systems and how their properties compare to planets in single-star systems. By studying this system in greater detail, perhaps we can gain insight into how the universe makes planets.”

The tilt of the planet suggests that it and the stars in the system may not have formed from the same disk of gas and dust, as is typical. The current theory to explain the planet’s tilt is that one of the other stars interfered with the planet’s orbit, its gravity kicking the planet into a different plane.

Editors' Recommendations

Georgina Torbet
Georgina is the Digital Trends space writer, covering human space exploration, planetary science, and cosmology. She…
James Webb detects water vapor in rocky planet’s atmosphere — maybe
This artist concept represents the rocky exoplanet GJ 486 b, which orbits a red dwarf star that is only 26 light-years away in the constellation Virgo. By observing GJ 486 b transit in front of its star, astronomers sought signs of an atmosphere. They detected hints of water vapor. However, they caution that while this might be a sign of a planetary atmosphere, the water could be on the star itself – specifically, in cool starspots – and not from the planet at all.

The hunt for habitable exoplanets is on, and with the James Webb Space Telescope, we finally have a tool that can not only detect the presence of a planet in another star system, but can also look at the composition of its atmosphere. That ability will eventually allow us to find Earth-like planets wthat are good candidates for searching for life, but measuring the atmosphere of something so far away isn't an easy matter.

Webb recently saw exciting signs in the form of water vapor detected in the vicinity of the exoplanet GJ 486 b. That could indicate the presence of water in its atmosphere, but it could also be from another source: the outer layer of the planet's host star. Researchers are working through the data and hope to use another of Webb's instruments to make the final call.

Read more
We now know what caused comet ‘Oumuamua’s strange orbit
An artist’s depiction of the interstellar comet ‘Oumuamua, as it warmed up in its approach to the sun and outgassed hydrogen (white mist), which slightly altered its orbit. The comet, which is most likely pancake-shaped, is the first known object other than dust grains to visit our solar system from another star.

Remember what feels like decades ago, when we were visited by a comet from another solar system in 2019? Interstellar comet ‘Oumuamua captured headlines when its cigar-shaped body was spotted following an unusual orbit through our solar system, and subsequent research suggested it might once have been part of a Pluto-like planet and was possibly pancake-shaped.

One thing particularly puzzled astronomers, though, because the comet was accelerating away from the sun in a path that seemed strange. Now, researchers say they have an explanation for its unusual pathway, and it isn't aliens -- it's a natural phenomenon called outgassing.

Read more
Weirdly large ‘forbidden’ exoplanet orbits a relatively tiny star
Artist's conception of a large gas giant planet orbiting a small red dwarf star called TOI-5205.

Astronomers have discovered a "forbidden" planet that appears to be far larger than should be possible given its circumstances. A team of researchers investigated a candidate exoplanet called TOI 5205b, first identified by NASA's Transiting Exoplanet Survey Satellite (TESS), and not only confirmed that the planet was there but also discovered that it has some baffling characteristics.

Artist's conception of a large gas giant planet orbiting a small red dwarf star called TOI-5205. Image by Katherine Cain, courtesy of the Carnegie Institution for Science

Read more