(ORDO NEWS) — Object 90377 Sedna, a distant trans-Neptunian object best known for its 11,390-year highly elliptical orbit, is currently en route to perihelion (its closest approach to the Sun) in 2076. After that, Sedna will again go into deep space and will not return for millennia, which makes this flight the only opportunity in life (or once in ~ 113 lives) to study an object from the far corners of our solar system.
There are currently no missions in the works to Sedna, but astronomers are beginning to plan for one, and the ideal launch date for such a mission is fast approaching, with the top two launch windows coming in 2029 and 2034.
Discovered in 2003 by Caltech astronomer Mike Brown and his team, Sedna was one of a series of potential dwarf planets (along with similarly sized bodies such as Haumea, Makemake, and Eris) that led to Pluto’s sinking in 2006.
As far as we can tell from Earth, Sedna is about the same size as Ceres, the largest object in the asteroid belt, but its composition and origin are very different. Its chemical composition suggests that it may be coated with a deep reddish organic compound known as tholins, the same material seen on Pluto and other Kuiper belt objects. Unlike Pluto, it is usually too cold here for the abundant methane on its surface to evaporate and fall back as snow.
What really sets Sedna apart from other known dwarf planet candidates is its enormous orbit, which takes it to 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 explaining how Sedna ended up in this position.
Perhaps the loudest theory is the possibility that an as-yet unknown ninth planet, perhaps ten times the size of Earth, disrupted Sedna’s orbit and threw it and several other objects into highly elongated orbits. A visit to Sedna probably won’t solve this particular puzzle, but it does tell us a lot about the composition of these extreme trans-Neptunian objects.
Getting to Sedna in a spaceship will be a daunting task. Even with the closest approach, Sedna will be only 76AE from the Sun. For comparison, Neptune is at 30AE, while the Voyager missions, launched in 1977, are only now crossing 150AE and 125AE, respectively. This means that you need to plan your launch time now.
When planning a mission to Sedna, the Voyager spacecraft is a good place to look for inspiration. As you know, they took advantage of the favorable arrangement of the planets to make a grand journey through the outer solar system, stealing energy from Jupiter in order to gain speed and reach their more distant goals.
For the journey to Sedna to be controlled, similar gravitational assistance would be required. A team of scientists led by Vladislav Zubko of the Space Research Institute of the Russian Academy of Sciences recently modeled a series of possible trajectories to Sedna, prioritizing a 2029 launch date as the most viable option.
They determined that the 2029 trajectory would take the spacecraft first to Venus and then back to Earth (twice) before passing Jupiter on its way to Sedna, with a flight time of about 20 years, but a more optimal range of 30 years. Longer flight times would increase the spacecraft’s altitude over Jupiter during gravity assist, reducing the time it takes to be exposed to the harmful radiation of the gas giant.
A 30-year flight plan would also mean a slower passage past Sedna, which would give more time to collect data about 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.
As a bonus, this trajectory will also lead the spacecraft past a 145 km diameter asteroid called Massalia, which will provide the team with an additional scientific target to explore as well as the ability to test the spacecraft’s systems.
The second trajectory proposed by the team will consist of a launch in 2034 and provide a similar additional flyby, this time around the metal asteroid 16 Psyche.
It is unclear at this point if the Sedna mission will actually make it to the launch pad with all the competing options available to mission planners in the next decade, but since this is our only chance in the next 11,000 years, the idea will definitely be properly considered.
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