Scientists have announced the discovery of a peculiar new object situated far beyond Neptune, in one of the coldest and most remote regions of our solar system.
This object, designated 2017 OF201, is icy, incredibly distant, and potentially massive enough to be classified as a dwarf planet. It completes a single orbit around the sun in approximately 25,000 years.
Researchers indicate that it is one of the most distant objects ever observed in space — and its existence could suggest that numerous other hidden worlds are still awaiting discovery.
The researchers described it as one of the most distant visible objects in our solar system and stated that its presence suggests that the vast expanse of space beyond Neptune, the outermost planet – and the region known as the Kuiper Belt – may not be as barren as previously thought. The Kuiper Belt is known to be populated by numerous icy bodies.
The object falls into a category known as trans-Neptunian objects, which orbit the sun at a distance greater than that of Neptune.
The researchers noted that 2017 OF201 was identified through seven years of observations by telescopes located in Chile and Hawaii.
“It is potentially large enough to qualify as a dwarf planet. Its orbit is very wide and eccentric, which means it experienced an interesting orbital migration path in the past,” said astrophysicist Sihao Cheng of the Institute for Advanced Study in Princeton, New Jersey, who led the study with collaborators Jiaxuan Li and Eritas Yang, graduate students at Princeton University.
Its estimated size is slightly smaller than Ceres, which is the smallest of the solar system’s five recognized dwarf planets with a diameter of approximately 590 miles (950 km). Pluto, the largest of these dwarf planets, has a diameter of about 1,477 miles (2,377 km).
The mass of 2017 OF201 is estimated to be about 20,000 times smaller than Earth’s and 50 times smaller than Pluto’s.
“We don’t know the shape yet. Unfortunately it is too far away and it is a bit difficult to resolve it with telescopes,” Cheng said. “Its composition is totally unknown yet, but likely similar to other icy bodies.”
The discovery was announced by the Minor Planet Centre of the International Astronomical Union, an international organization of astronomers, and detailed in a study posted on the open-access research site arXiv. The study has not yet undergone peer review.
Earth’s orbital distance from the sun is defined as an astronomical unit. Currently, 2017 OF201 is located at a distance of 90.5 astronomical units from the sun – meaning it is 90.5 times as far as Earth.
However, at its furthest point during its orbit, 2017 OF201 is more than 1,600 astronomical units from the sun, while its closest orbital point is about 45 astronomical units. This implies it is sometimes closer to the sun than Pluto, whose orbital distance ranges from 30 to 49 astronomical units as it traverses an elliptical path around the sun.
The researchers hypothesize that the extreme orbit of 2017 OF201 may have been caused by a long-ago close encounter with the gravitational influence of a giant planet.
“We still don’t know much about the solar system far away because currently it is difficult to directly see things beyond about 150 astronomical units,” Cheng said. “The presence of this single object suggests that there could be another hundred or so other objects with similar orbit and size. They are just too far away to be detectable right now.”
The five dwarf planets recognized by the International Astronomical Union are, in order of distance from the sun: Ceres, the largest object in the asteroid belt between Mars and Jupiter; followed by Pluto, Haumea, Makemake, and Eris, all of which orbit beyond Neptune.
The organization distinguishes between a planet and a dwarf planet. A planet must orbit its host star – in our case, the sun – be mostly round, and sufficiently large that its gravitational strength has cleared any other similarly sized objects near its orbit. A dwarf planet must also orbit the sun and be mostly round, but it has not cleared its orbit of other objects.
Cheng stated that the discovery of 2017 OF201 has implications for hypotheses concerning the potential existence of a ninth planet in our solar system, often referred to as Planet X or Planet Nine.
This is because 2017 OF201’s orbit does not conform to the clustering pattern exhibited by other known trans-Neptunian objects. Some scientists had theorized that such clustering was a result of the gravitational pull of a yet-to-be-discovered planet.
“The existence of 2017 OF201 as an outlier to such clustering could potentially challenge this hypothesis,” Cheng concluded.
