A team of planetary researchers at the University of Colorado at Boulder has offered up a new theory for the existence of strange trans-Neptunian objects — called ‘detached objects’ — such as the minor planet Sedna.
An artist’s concept of the minor planet Sedna; the Sun appears as an extremely bright star instead of a large, warm disc observed from Earth; in the distance is a hypothetical small moon, which scientists believe may be orbiting this distant body. Image credit: NASA / JPL-Caltech.
Our Solar System contains a large population of icy bodies stretching well beyond the orbit of Neptune.
These objects are remnants from the early formation of the Solar System that were scattered outward from their birth location by Neptune. But not all fit the bill.
Sedna, one particularly massive trans-Neptunian object, does not conform to the scattering pattern.
It orbits the Sun at a distance of 8 billion miles but appears separated from the rest of the Solar System.
One theory for this unusual dynamics is that the hypothetical Planet Nine may have disturbed the orbits of Sedna and other detached objects.
But Dr. Ann-Marie Madigan and co-authors calculated that the orbits of Sedna and its ilk may result from these bodies jostling against each other and space debris in the outer Solar System.
“There are so many of these bodies out there. What does their collective gravity do? We can solve a lot of these problems by just taking into account that question,” Dr. Madigan said.
Using computer simulations, the researchers came up with one possible answer. They calculated that these icy objects orbit the Sun like the hands of a clock.
The orbits of smaller objects, such as asteroids, however, move faster than the larger ones, such as Sedna.
“You see a pileup of the orbits of smaller objects to one side of the Sun,” said Jacob Fleisig, first author of the study.
“These orbits crash into the bigger body, and what happens is those interactions will change its orbit from an oval shape to a more circular shape.”
In other words, Sedna’s orbit goes from normal to detached entirely because of those small-scale interactions.
The team’s observations also fall in line with research from 2012, which observed that the bigger a detached object gets, the farther away its orbit becomes from the Sun.
The scientists presented their findings June 4 at the 232nd Meeting of the American Astronomical Society in Denver, Colorado.
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Jacob Fleisig et al. 2018. On the Detachment of Massive Trans-Neptunian Objects. 232nd Meeting of the American Astronomical Society, abstract # 123.04
