Most of us grew up saying our solar system was made up of a sun and nine planets — including our distant sibling Pluto. In 2005, however, Pluto lost its standing as a planet, owing its downfall in large part to discoveries of other planetary bodies like Eris, a dwarf planet of the same basic size as Pluto that also shares our celestial zip code. Soon more dwarf planets were discovered, making Pluto a bit less special than it was once considered. Ultimately, the decision was made to strip Pluto of its title, making it the king of the dwarf planets, rather than the runt of the group.
Since then, our solar system’s planetary count has officially been eight… but that may not be the case for long. There have long been legends of mysterious planets (and even dwarf stars) lurking in the distant expanse of our solar system, beyond where the sun’s light can reach with enough effect to illuminate it in our skies. Some have argued such a planet could be responsible for the cyclical extinction events that seem to occur on Earth every 31 million years or so. The theory suggests that a massive orbital path may take earth’s mysterious cousin into the interior of the solar system periodically, disrupting the state of the asteroid belt via gravitational forces and creating an environment ripe for asteroid strikes.
Legends of “Planet X” were more or less dismissed by the scientific community, however, until 2016 — when one of the very men responsible for Pluto’s demotion helped to publish a paper proposing that there may really be another planet way out in the nose-bleed section of our own solar system.
“We have found evidence that there’s a giant planet in the outer solar system,” Astronomer Mike Brown said at the time. “By ‘giant’ we mean the size of Neptune, and when we say ‘outer solar system’ we mean 10 to 20 times farther away than Pluto.”
Now, “evidence” in this case is a tricky word because, at that distance, the sun’s light doesn’t reflect on planets as it does in the local area. In other words, even our most advanced telescopes would have trouble picking out even a Neptune sized planet against the massive starry backdrop that is space. Instead, Brown and his team used observations of other already identified orbital bodies and good old fashioned mathematics to form their theory. In effect, they see the way dwarf planets are behaving along their orbital path out into the Kuiper Belt (a second massive asteroid belt that encircles our solar system) and have recorded behavior that could only be explained by the presence of a massive gravitational force out in the far reaches of the solar system.
Since then, astronomers all over the world have continued the search for this mysterious planet, and earlier this week a team out of Northern Arizona University announced a new discovery that suggests it may indeed be possible for earth’s own solar system to still be keeping some secrets. They found yet another distant orbital body, not unlike Pluto that had yet to be discovered, but more importantly, it’s orbital pattern also suggests the presence of a massive planet we have yet to identify.
“These distant objects are like breadcrumbs leading us to Planet X. The more of them we can find, the better we can understand the outer Solar System and the possible planet that we think is shaping their orbits—a discovery that would redefine our knowledge of the Solar System’s evolution,” Astronomer Scott Sheppard said of his team’s findings.
If this new discovery (which astronomers have named “The Goblin”) does lead to Planet X, Brown knows there’s a chance he may be asked to name it.
“My daughter, Lilah, has suggested that we call it Pluto. That way Pluto can be a planet again.” He joked.