Why 2029 is crucial for studying the solar system’s most controversial orb

Object 90377 Sedna – a distant transneptunian 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 set off again in deep space and not return for millennia, making this flyby a unique opportunity (or, once in ~ 113 lifetimes) to study an object from the far reaches of our solar system.

There are no missions to Sedna in preparation yet, but astronomers are starting to anticipate this possibility. The ideal launch date for such a mission is fast approaching, with two of the best launch windows coming in 2029 and 2034.

Sedna was discovered in 2003 by Caltech astronomer Mike Brown and his team and was one of a series of potential dwarf planets (alongside similarly sized bodies like Haumea, Makemake, and Eris) whose discovery led to the demotion of Pluto in 2006.

As far as we can tell from a distance, Sedna is roughly the same size as Ceres, the largest object in the asteroid belt, but its makeup and origins are very different. Its chemical makeup suggests that it could be coated with deep reddish organic compounds called tholins, the same material seen on Pluto and other objects in the Kuiper Belt.

Unlike Pluto, it is usually too cold for the methane abundant on its surface to evaporate and fall back as snow, although Sedna may briefly gain an atmosphere of nitrogen as the Sun approaches.

What sets Sedna apart from other known candidate dwarf planets is its enormous orbit, which brings it to the inner edge of the Oort Cloud, the furthest region in the solar system, where long-lived comets lurk. There are several competing theories as to how Sedna got into this position.

Perhaps the most publicized theory is the possibility that an as yet unknown ninth planet, perhaps 10 times the size of Earth, disrupted Sedna’s orbit and dragged her, along with several other objects, onto very elongated eye sockets. Visiting Sedna probably won’t solve this particular mystery, but it will tell us a lot about the makeup of these extreme Transneptunian objects.

The orbit of candidate dwarf planet 90377 Sedna (red) relative to Jupiter (orange), Saturn (yellow), Uranus (green), Neptune (blue) and Pluto (purple).Wikimedia Commons

Reaching Sedna with a spaceship will not be an easy task. Even at its closest approach, Sedna will only come to about 76 AU from the Sun. By way of comparison, Neptune measures about 30 AU, and the Voyager missions, launched in 1977, have just crossed 150 AU and 125 AU respectively. This means that the time to throw is sooner rather than later.

When planning a mission to Sedna, Voyager spacecraft are not a bad place to look for inspiration. They took advantage of a lucky alignment of planets to take a grand tour of the outer solar system, stealing energy from Jupiter to gain speed and hit their more distant targets.

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 series of possible trajectories to Sedna, prioritizing a launch date of 2029 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, thereby reducing the time spent being exposed to harmful radiation from the gas giant.

A 30-year flight plan would also mean going through Sedna more slowly, giving more time to collect data on the object. Choosing this option would give the spacecraft a relative speed of 13.70 km / s (29,000 mph) during its passage through Sedna, comparable to the speed at which New Horizons approached Pluto in 2015.

90377 Sedna as seen by the Hubble Space Telescope in 2004.Nasa

As an added bonus, this trajectory would also take the spacecraft past a 145 km (90 mile) diameter asteroid named Massalia, giving the team an additional scientific target to study, as well as a chance to test the systems. of the spaceship.

A second trajectory proposed by the team would consist of a launch in 2034 and provide a similar additional flyby, this time over the metallic asteroid 16 Psyche.

At this time, it’s unclear whether a mission to Sedna will hit the launch pad with all of the competing options available to mission planners in the next decade or so. But since this is our only chance for the next 11,000 years, the idea will certainly be given careful consideration.

This article was originally published on Universe today by Scott Alan Johnston. Read it original article here.


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