The furthest object known to be a trans-Neptunian is currently on its way towards perihelion in 2076). This flyby of an object from the far reaches of our solar system will be a once-in-a-lifetime opportunity to study an object from the far reaches of our solar system. The ideal launch date for a mission to Sedna is approaching fast, with two of the best launch windows coming up in 2029 and 2034.
In 2003 Caltech astronomer Mike Brown and his team discovered a dwarf planet called Sedna, which was one of a series of similar-sized bodies. We can't tell from a distance if it's the same object as Ceres, but it is very different. It may be covered in deep reddish organic compounds known as tholins, similar to the material seen on Pluto and other Kuiper belt objects. It is too cold for the methane on its surface to evaporate and fall back as snow, and it may gain an atmosphere of nitrogen as it approaches the Sun.
There are other dwarf planet candidates, but they all have the same thing: an enormous orbit, which takes them out towards the Oort cloud, where long-period comets can be found. There are many theories about how she ended up here. The most high-profile theory is that a ninth planet, ten times the size of Earth, could have disrupted Sedna's path and swept it and several other objects out into the farthest reaches of our solar system. It won't solve the mystery, but it will give us a good idea of the composition of these objects.
The dwarf planet candidate 90377 Sedna has a lower than average altitude compared to other planets. Credit: Szczureq/kheider/NASA
It won't be easy to reach Sedna with a spaceship. The closest approach will only bring Sedna about 76AU from the Sun. Neptune is about 30AU, while the Voyager missions are just now crossing 150AU and 125AU. The time to launch is sooner than later.
In planning a mission to Sedna, the Voyager spacecraft are a good place to look for inspiration. They took advantage of a lucky alignment of planets to take a tour of the outer Solar System, stealing energy from Jupiter to reach their more distant targets. Similar gravity assists will be required to make the trip to Sedna manageable. A group of scientists from the Space Research Institute of the Russian Academy of Sciences recently modeled a series of possible trajectory options to Sedna, and chose a 2029 launch date as the most feasible option.
The 2029 trajectory would take the spaceship to Venus first, then back to Earth twice, and finally to Jupiter, with flight times as short as 20 years but more optimal in the 30-year range. The longer flight time would increase the altitude of the craft over Jupiter and reduce the amount of time spent exposed to the gas giant.
A 30-year flight plan would give more time to gather data on the object. This option would give the spacecraft a relative speed of 13.70 km/s, which is1-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-65561-6556
The Hubble Space Telescope shows 90377 Sedna. Credit: NASA.
This trajectory would allow the team to study an additional target, as well as test the systems of the craft, if they choose to do so.
A second trajectory proposed by the team would include a 2034 launch and provide another flyby of the metallic asteroid 16 Psyche.
It is not clear if a mission to Sedna will actually make it to the launch pad with all the competing options available, but as it is our only chance in the next 11,000 years, the idea is sure to be given due diligence.
The paper is available in a pre-print format on ArXiv.
The artist has created a rendering of Sedna. NASA/JPL-Caltech/R. Hurt.
