|Image Credit: NASA|
Object 90377 Sedna, a distant trans-Neptunian object best known for its highly elliptical orbit of 11,390 years, is currently en route to perihelion (its closest approach to the Sun) in 2076. After that, Sedna will return to ‘space. deep and will not return for millennia, making this overview a once in a lifetime opportunity (or, once in ~ 113 lifetimes) to study an object from the far reaches of our solar system. There are no Sedna missions in the works yet, but astronomers are beginning to plan for the possibility and the ideal launch date for such a mission is fast approaching, with two of the best launch windows in 2029 and 2034.
Sedna was discovered in 2003 by Caltech astronomer Mike Brown and his team, and it was one of a number of potential dwarf planets (along with similarly sized bodies such as Haumea, Makemake, and Eris) whose discovery led to the degradation of Pluto in 2006. As the best we can tell from a distance is that Sedna is roughly the same size as Ceres, the largest object in the asteroid belt, but its composition and origins are very different. Its chemical makeup suggests that it may be covered in deep reddish organic compounds known as tholins, the same material seen on Pluto and other Kuiper belt objects. Unlike Pluto, it is generally too cold for the abundant methane on its surface to evaporate and fall as snow, although Sedna may briefly gain an atmosphere of nitrogen as it approaches the Sun.
What really sets Sedna apart from the other known dwarf planet candidates is its massive orbit, which carries it toward the inner edge of the Oort cloud, the most distant region of the Solar System, where long-period comets lurk. There are several competing theories to explain how Sedna ended up in this position. Perhaps the most prominent theory is the possibility that a still unknown ninth planet, perhaps ten times the size of Earth, disrupted Sedna’s orbit and dragged it along with several other objects into very elongated orbits. Visiting Sedna probably won’t solve this particular mystery, but it will tell us a lot about the composition of these extreme trans-Neptunian objects.
|The orbit of the dwarf planet candidate 90377 Sedna (red) compared to Jupiter (orange), Saturn (yellow), Uranus (green), Neptune (blue) and Pluto (purple). Credit: Szczureq / kheider / NASA (Wikimedia Commons).|
When planning a mission to Sedna, Voyager spacecraft are not a bad place to seek inspiration. They have been known to harness a fortunate alignment of planets to go on a grand tour of the outer Solar System, stealing energy from Jupiter to gain speed and reach their more distant goals. Similar gravity aids will be needed to make the trip to Sedna manageable. A team of scientists led by Vladislav Zubko of the Russian Academy of Sciences Institute for Space Research recently modeled a number of possible trajectories to Sedna, favoring a 2029 launch date as the most feasible option.
The 2029 trajectory, they determined, would take the spacecraft to Venus first, then back to Earth (twice), before passing Jupiter on the way to Sedna, with flight times as short as 20 years but most optimally in the 30 year range. The longer flight time would increase the spacecraft’s altitude above Jupiter during gravity assist, reducing the time of exposure to harmful radiation from the gas giant.
A 30-year flight plan would also mean passing Sedna more slowly, providing more time to collect data on the object. Choosing this option would give the spacecraft a relative speed of 13.70 km / s as it passed Sedna, comparable to the speed at which New Horizons approached Pluto in 2015.
|90377 Sedna as seen by the Hubble Space Telescope in 2004. Credit: NASA.|
A second trajectory proposed by the team would consist of a launch in 2034 and provide a similar additional flyby, this time of the metallic asteroid 16 Psyche.
At the moment, it’s unclear if a mission to Sedna will actually hit the launch pad with all the competitive options available to mission planners in the next decade, but since it’s our only chance in the next 11,000 years, the idea surely it will. receive due diligence.
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Fountain: Universe today