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Kepler-88 has a new king! Planet three-times Jupiter's mass discovered in alien star system

It appears that planetary heavyweight Kepler-88 c, which orbits the sunlike star Kepler-88, is no longer the gravitational god of the exoplanets in the Kepler-88 system, according to a new study. A new world was recently confirmed in the system, tipping the scales at three times the mass of solar system giant Jupiter.

Led by a team of astronomers at the University of Hawaii Institute for Astronomy (UH IfA), the research — which is based on six years of data taken from W.M. Keck Observatory on Mauna Kea in Hawaii — uncovered a previously undetected third exoplanet orbiting Kepler-88. Named Kepler-88 d, the newfound planet completes slow-moving laps around its host star every four years. 

It was the keen telescopic eye of the High-Resolution Echelle Spectrometer (HIRES) instrument affixed to the 10-meter Keck I telescope that revealed to lead author Lauren Weiss, a Beatrice Watson Parrent Postdoctoral Fellow at UH IfA, her team had made a game-changing discovery.

Video: Exoplanet Kepler-88 d is 3X more massive than Jupiter
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Keck Observatory sits atop Mauna Kea in Hawaii. (Image credit: NASA/JPL)

"At three times the mass of Jupiter, Kepler-88 d has likely been more influential in the history of the Kepler-88 system than the so-called King, Kepler-88 c, which is only one Jupiter mass," Weiss said. "So maybe Kepler-88 d is the new supreme monarch of this planetary empire — the empress."

The Kepler-88 system, which lies over 1,200 light-years away from Earth in the constellation of Lyra, the harp, has drawn attention from astronomers ever since the discovery of its first two exoplanets in 2013. The observations revealed that Kepler-88 c, the more massive of the two exoplanets, and its gaseous sibling Kepler-88 b appear to interact around their host star in a striking way.

For one, the "sub-Neptune" exoplanet Kepler-88 b completes an orbital lap every 11 days, almost exactly half the time it takes Kepler-88 c to finish a circuit. Since Kepler-88 c, the outer planet, is 20 times more massive than Kepler-88 b, the larger planet's gravity affects the orbit of the inner world when the two planets pass each other in orbit. In other words, for every two orbits Kepler-88 b achieves, it gets "pumped" by its gigantic sibling, according to a statement from the Keck Observatory.

Kepler-88 d has a mass three-times that of our solar system's Jupiter (Image credit: W. M. Keck Observatory/Adam Makarenko )

What astronomers have observed between the alien worlds is a bizarre and striking dynamic known as mean motion resonance; two orbits that seem to behave in a clockwork fashion — it's energetically efficient, according to Weiss and her team, and similar to a parent pushing a child on a swing.

It was with the help of NASA's now-defunct Kepler Space Telescope (which officially ceased operations on Oct. 30, 2018 when the spacecraft ran out of fuel), that the orbital timing of the planets in the Kepler-88 system was gained with precision. Kepler was able to use the art of transits — an exoplanet detection technique in which astronomers watch for planets passing in front if their host stars — to gain the readings, known as transit timing variations.

Although transit timing variations (TTVs) have been detected in a few dozen planetary systems, Kepler-88 b has some of the largest timing variations. With transits arriving up to half a day early or later than predicted, the system is known as "the King of TTVs," the researchers said in the statement.

Heading back to our solar system, Jupiter holds the cards when it comes to being the king of gravitational influence. Twice the mass of ringed giant Saturn and 300 times heftier than Earth, even the slightest movement is felt by the other worlds of cosmic neighborhood: from Mars to the team of comets that — according to observations of comet 46P/Wirtanen — delivered water to a parched young Earth billions of years ago.

Whether Kepler-88 d also has the influence to direct water-bearing comets to newly-developed rocky worlds is of importance to the team of researchers, Weiss said.

The new research was published April 29 in the Astronomical Journal.

Gemma Lavender is the author of Quantum Physics in Minutes (Quercus, 2017) and Haynes Owner's Workshop Manual: Milky Way (Haynes Publishing, 2019), among other books. Follow her on Twitter @Gemma_Lavender. Follow us on Twitter @Spacedotcom and on Facebook

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Gemma Lavender

Gemma is content director of science and space magazines How It Works and All About Space, history magazines All About History and History of War as well as Science, Technology, Engineering, Arts and Mathematics (STEAM) kids education brand Future Genius. She is the author of several books including "Quantum Physics in Minutes", "Haynes Owners’ Workshop Manual to the Large Hadron Collider" and "Haynes Owners’ Workshop Manual to the Milky Way". She holds a degree in physical sciences, a Master’s in astrophysics and a PhD in computational astrophysics. She was elected as a fellow of the Royal Astronomical Society in 2011. Previously, she worked for Nature's journal, Scientific Reports, and created scientific industry reports for the Institute of Physics and the British Antarctic Survey. She has covered stories and features for publications such as Physics World, Astronomy Now and Astrobiology Magazine.