But if they're not being tugged on by the planets we know about, that leaves the door open for interactions with objects we haven't yet discovered, like Planet Nine.
The existence of a space object had been predicted in 2015.
"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 hard", Tholen said in a statement. Targeted hunts can produce biased results - for example, the appearance of clustering where none may actually exist, he explained.
It joins other objects Sheppard and his team have found on the edge of the solar system since 2012. 2015 TG387 can be seen moving between the images near the center while the more distant background stars and galaxies do not move.
Tholen first observed 2015 TG387 in October of 2015 at the Japanese Subaru 8-meter telescope on Maunakea, Hawaiʻi.
A new discovery makes Planet Nine seem even more likely. Follow-up observations at the Magellan telescope at Carnegie's Las Campanas Observatory in Chile and the Discovery Channel Telescope in Arizona were obtained in 2015, 2016, 2017 and 2018 to determine 2015 TG387's orbit. Pluto is about 34 AU from the sun, so 2015 TG387 is two and a half times farther from the sun than the former ninth planet.
2015 TG387 was discovered about 80 astronomical units (AU) from the sun. So 2015 TG387 is way, way out there. The Goblin is one of just a few objects whose elliptical orbits never take them closer to the sun than Neptune.
Scott Sheppard said, 'These so-called Inner Oort Cloud objects like 2015 TG387, 2012 VP113, and Sedna are isolated from most of the solar system's known mass, which makes them immensely interesting. At about 300 km (186 miles) wide, it is on the small side of being a dwarf planet.
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"We think there are thousands of these, and majority are too distant to detect", Sheppard said. "We don't even know the color of the object; we haven't gotten any spectroscopy on the object yet, or anything like that".
The two other dwarf planets are Sedna, discovered in 2003, which is about 620 miles (1,000 kilometers) across, and 2012 VP113, about 310 miles (500 kilometers). That's where Planet X comes in. According to them, the orbits of those dwarf planets and asteroids suggests a hidden planet is lurking somewhere out there, messing up those orbits with its gravity.
Astronomers have found a small object far beyond Pluto that orbits the sun in a lonely, oblong loop, a discovery that supports the notion of a larger, more distant planet - often referred to as Planet X - wandering the edge of our solar system. An orbit of that size means the new dwarf planet takes around 40,000 years to complete one single lap around the sun.
Discovering Planet X would "redefine our knowledge of the solar system's evolution", he added.
"Objects such as 2015 TG387 allow us to probe not only the makeup of the solar system itself but also the gravitational mechanisms that sculpt it", said Konstantin Batygin, a planetary scientist at the California Institute of Technology who was not involved with the observation.
"When we put a hypothetical distant massive Planet X into our numerical simulations of the solar system, TG387 is still stable", he says. Sheppard wrote in an article for Nature in 2014 that objects like the Goblin would move in a particular way to avoid a possible "Planet Nine". And he says it's not at all surprising that astronomers haven't spotted it yet.
Meanwhile, the newfound planet Goblin very cold.
"And most of our surveys to date do not go that faint, do not go that deep". Perhaps someday, we'll find it.
To put that in perspective, pretend that you could shrink the solar system so that the sun is in NY and Pluto lies in Los Angeles.