New Delhi: The solar system may get a ninth planet again as scientists have published evidence of a possible planet following an elongated orbit in the outer solar system. The object, which the researchers have nicknamed Planet Nine, has a mass of about 10 times that of Earth and orbits about 20 times farther from the Sun on average than Neptune.
California Institute of Technology researchers Konstantin Batygin and Mike Brown have provided theoretical evidence of the planet’s existence using mathematical modelling and computer simulations, but have not observed the object directly. “This would be a real ninth planet,” says Brown, the Richard and Barbara Rosenberg Professor of Planetary Astronomy. “There have only been two true planets discovered since ancient times, and this would be a third. It’s a pretty substantial chunk of our solar system that’s still out there to be found, which is pretty exciting,” Brown added in a press release.
Brown noted that the object which is 5,000 times the mass of Pluto is sufficiently large, leaving no question about it being a true planet. Unlike the class of smaller objects now known as dwarf planets which is how Pluto was classified, Planet Nine gravitationally dominates its neighbourhood in the solar system.
In the Astronomical Journal, the researchers showed how Planet Nine helps explain a number of mysterious features of the field of icy objects and debris beyond Neptune known as the Kuiper Belt.
“Although we were initially quite skeptical that this planet could exist, as we continued to investigate its orbit and what it would mean for the outer solar system, we become increasingly convinced that it is out there,” says Batygin, an assistant professor of planetary science. “For the first time in over 150 years, there is solid evidence that the solar system’s planetary census is incomplete,” Batygin added in a Caltech release.
The investigation on the existence of Planet Nine began in 2014 when a former postdoc of Brown’s, Chad Trujillo, and his colleague Scott Sheppard published a paper, noting that 13 of the most distant objects in the Kuiper Belt are similar with respect to their orbits. They suggested the possible existence of a planet which although Brown thought was unlikely, he decided to look into it.
Batygin and Brown found that the six most distant objects in Kuiper follow elliptical orbits that point in the same direction in space. “It’s almost like having six hands on a clock all moving at different rates, and when you happen to look up, they’re all in exactly the same place,” explained Brown. “Basically it shouldn’t happen randomly. So we thought something else must be shaping these orbits,” Brown added.
It was then that Batygin and Brown found that if they ran their simulations with a massive planet in certain, the distant Kuiper Belt objects in the simulation assumed the alignment that is actually observed. Scientists are still searching for the planet to make a direct observation using large telescopes.