Strange objects discovered past Neptune
Asix-year search of space beyond the orbit of Neptune has netted 461 newly discovered objects. These objects include four that are more than 230 astronomical units (AU) from the Sun – an astronomical unit is the average distance from Earth to the Sun, which is about 93 million miles. These extraordinarily distant objects might shed light on Planet Nine, a theoretical body that might be hiding in deep space, its gravity affecting the orbits of some of the rocky objects at the Solar System’s edge.
The new observations come courtesy of the Dark Energy Survey, an effort to map the universe’s galactic structure and dark matter that began in 2013. Six years of observations from the Víctor M. Blanco Telescope at the Cerro Tololo Inter-american Observatory in Chile yielded a total of 817 confirmed new objects, 461 of which are now being described for the first time in a new paper.
The objects in the study are all at least 30 AU away, in a region of the Solar System that is almost unimaginably dark and lonely. More than 3,000 trans-neptunian objects, or TNOS, have been identified in these icy reaches.
They include dwarf planets such as Pluto and Eris, as well as small Kuiper Belt objects like Arrokoth, a rocky body visited by the New Horizons spacecraft in 2019. The Kuiper Belt is a region of icy objects orbiting between about 30 and 50 AU from the Sun.
Of the 461 objects described for the first time in the new paper, a few stand out. Nine
are known as extreme trans-neptunian objects, which have orbits that swing out at least 150 AU from the Sun. Four of those are very extreme, with orbital distances of 230 AU. At these distances, the objects are hardly affected by Neptune’s gravity, but their strange orbits suggest an influence from outside the Solar System. Some researchers think that influence might be an elusive and undiscovered planet, dubbed Planet Nine. The newly discovered objects could thus help researchers hone in on the possible Planet Nine, or disprove its existence.
The researchers also found four new Neptune Trojans. Trojans are bodies that share the orbits of a planet or moon. In this case the objects share Neptune’s orbit around the Sun. They also observed Comet Bernardinelli-bernstein, named after the two lead authors of the paper, University of Pennsylvania cosmologist Gary Bernstein and University of Washington postdoctoral scholar Pedro Bernardinelli. The two researchers were the first to spot the comet in the Dark Energy Survey dataset. The Bernardinelli-bernstein comet may be up to 100 miles wide. It hails from the Oort Cloud, another layer of icy objects even more distant than the Kuiper Belt.
At least 155 of the newly discovered objects are what astronomers call ‘detached’. This means that they are far enough from Neptune that the large planet’s gravity doesn’t affect them much; instead they’re mostly tied to the Solar System by the distant pull of the Sun. Detached objects, sometimes known as extended scattered disc objects, tend to have huge elliptical orbits.
The Dark Energy Survey wasn’t meant as a search for trans-neptunian objects. Its goals were to characterise the theoretical dark energy that affects the universe’s accelerating expansion. Nevertheless, the data from the survey contains 20 per cent of all currently known TNOS, covering an eighth of the sky.