A planet in an unlikely orbit around a binary 336 light years away may offer a clue to the hypothetical planet Nine that is being sought in the outer reaches of our solar system.
This is the first time that astronomers have been able to measure the motion of a massive Jupiter-like planet that it is orbiting far away from its host stars and the visible debris disk.
This disk is similar to our icy small body Kuiper Belt beyond Neptune. In our own solar system, the supposed Planet Nine would also be a long way from the Kuiper Belt in an equally strange orbit. Although the search for a Planet Nine continues, This discovery of exoplanets is evidence that such strange orbits are possible.
“This system makes a potentially unique comparison with our solar system,” he explained. it’s a statement the lead author of the article, Meiji Nguyen of the University of California, Berkeley. ‘It is far apart from its host stars in an eccentric and highly misaligned orbit, just like the prediction for Planet Nine. This raises the question of how these planets formed and evolved to end up in their current configuration.
The system where this gas giant resides is only 15 million years old. This suggests that our Planet Nine, if it exists, it could have formed very early in the evolution of our 4.6 billion-year-old solar system.
The 11-mass exoplanet that of Jupiter called HD 106906 b was discovered in 2013 with the Magellan Telescopes at the Las Campanas Observatory in the Atacama Desert of Chile. However, astronomers did not know anything about the planet’s orbit. This required something that only the Hubble Space Telescope could do: collect very precise measurements of the rover’s movement over 14 years with extraordinary precision. The team used data from the Hubble archive that provided evidence for this movement.
ORBITAL PERIOD OF 15,000 YEARS
The exoplanet resides extremely far from its pair of bright, young stars, more than 730 times the distance from Earth to the Sun, or nearly 1.1 billion kilometers. This wide separation made it enormously difficult to determine the 15,000-year-long orbit in a relatively short time span of Hubble observations.. The planet moves very slowly along its orbit, given the weak gravitational pull of its very distant parent stars.
The Hubble team was surprised to discover that the remote world has an extreme orbit that is highly misaligned, elongated, and external to the debris disk that surrounds the exoplanet’s twin stars. The debris disk itself looks very unusual, perhaps due to the gravitational pull of the rogue planet.
So how did the exoplanet get into such a distant and strangely inclined orbit? The prevailing theory is that it formed much closer to its stars, about three times the distance that Earth is from the Sun. But drag within the system’s gas disk caused the planet’s orbit to decline., which forced him to migrate inwards, towards his star pair.
The gravitational effects of the spinning twin stars brought it into an eccentric orbit that nearly threw it out of the system and into the void of interstellar space. Then a passing star from outside the system stabilized the exoplanet’s orbit and prevented it from leaving its home system.
Using precise distance and motion measurements from the European Space Agency’s Gaia study satellite, team members Robert De Rosa, from the European Southern Observatory in Santiago, Chile, and Paul Kalas, from the University of California, identified candidate passing stars in 2019.
In a study published in 2015, Kalas led a team that found circumstantial evidence of the planet’s runaway behavior: the system’s debris disk is strongly asymmetrical, rather than a circular distribution of material in the shape of a “pizza pie.” One side of the disk is truncated with respect to the opposite side, and it is also vertically disturbed rather than restricted to a narrow plane as seen on the opposite side of the stars.
“The idea is that every time the planet gets closer to the nearest binary star, it shakes up the material on the disk,” De Rosa explains.
So every time the planet passes, it truncates the disk and pushes it up one side. This scenario has been tested with simulations of this system with the planet in a similar orbit; this was before we knew what the orbit of the planet was.