Search for Planet Nine turns up a way-out dwarf planet that’s called ‘The Goblin’
The International Space Station leaves a streak above the Subaru Telescope in a long-exposure image. Observations using the Subaru Telescope led to the discovery of the mini-world known as The Goblin. (Subaru Telescope / NAOJ Photo / Hideaki Fujiwara)
While searching for a hypothetical Planet Nine, astronomers found a distant mini-world that’s been given a spooky nickname: “The Goblin.”
The icy object was found at a distance of about 80 astronomical units from the sun, which translates to 7.4 billion miles. (One astronomical unit, or AU, equals 93 million miles, which is the distance between Earth and the sun.) That’s more than twice as far away as dwarf planet Pluto.
A research team led by Scott Sheppard of the Carnegie Institution of Science first spotted The Goblin just before Halloween in 2015. That timing, plus the fact that it was given the numerical designation 2015 TG387, gave rise to the trick-or-treat nickname. (T.G. … Get it?)
It took almost three more years of observations to nail down The Goblin’s oddball orbit, which ranges between 65 and 2,300 AU from the sun over the course of a 40,000-year circuit. The discovery was finally announced on Monday in a circular from the International Astronomical Union’s Minor Planet Center, and a paper with the full details has been submitted to The Astronomical Journal.
The Goblin joins a class of other oddballs called Inner Oort Cloud objects, which skirt a zone of the solar system where millions of comets are thought to lurk. Other examples of the class include Sedna and 2012 VP113 (which carries the nickname Biden in honor of the former veep.)
The Goblin’s orbit ranges far beyond the outer reaches of Pluto’s home in the Kuiper Belt, as well as other Inner Oort Cloud Objects such as 2012 VP113 (also known as Biden) and Sedna. (Carnegie Institution for Science / Roberto Molar Candanosa and Scott Sheppard)
The weird orbits of those worlds are consistent with the hypothesis that a distant planet larger than Earth, known as Planet Nine or Planet X, is exerting its gravitational influence. Astronomers have narrowed down the search area for Planet Nine but have not yet found it.
“These distant objects are like bread crumbs leading us to Planet X,” Sheppard said today in a news release. “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.”
Is the Goblin a dwarf, like Pluto? With an estimated diameter of 200 miles, it’s thought to be just massive enough to crush itself into a round shape, which would fit the definition for a dwarf planet. And if Sheppard and his colleagues are right, there could be a veritable gaggle of Goblins out there.
“We think there could be thousands of small bodies like 2015 TG387 out on the solar system’s fringes, but their distance makes finding them very difficult,” study co-author David Tholen of the University of Hawaii said. “Currently we would only detect 2015 TG387 when it is near its closest approach to the sun. For some 99 percent of its 40,000-year orbit, it would be too faint to see.”
The discovery drew upon data from Japan’s Subaru Telescope in Hawaii, the Discovery Channel Telescope and the Large Monolithic Imager at Lowell Observatory in Arizona, and the 6.5-meter Magellan Telescopes in Chile.
In addition to Sheppard and Tholen, the authors of “A New High Perihelion Inner Oort Cloud Object” include Chad Trujillo and Nathan Kalb.