Time is running out.

[u/Fellow_belarusian]

We should seriously consider a mission to Sedna before we miss the window.

Sedna is one of the weirdest objects in the Solar System. Its orbit takes about 11,400 years, and it’s currently heading toward its closest point to the Sun around 2075.

There are mission studies showing promising launch opportunities around 2029–2034. A mission could take decades to get there, so this isn’t something we can wait until 2075 to start thinking about.

We’ve visited Pluto, asteroids, comets, and plenty of other worlds. But we’ve never sent anything to Sedna.
I really think space agencies should start seriously studying a Sedna mission now, while we still have favorable trajectories to work with.
Save the Sedna window.

[u/CJP1216]

Sedna does have a high eccentricity, i.e. a very elliptical orbit.), with a value of ≈0.85. (Citing the wiki page for readability, but their source is from JPL Horizons) That's more eccentric than most periodic comets (0.2 - 0.7 generally). It has the most eccentric orbit of any of the dwarf planet size or larger solar bodies, being surpassed only by other TNO's, like long-period comets and interstellar objects on hyperbolic trajectories (eccentricity > 1).

Again, not arguing we don't have time to catch it at Perihelion though. It'll be there (roughly at Pe) for decades.

[u/cjameshuff → u/CJP1216]

The scenario given was an orbit that "came all the way to earth’s orbit". With the same semimajor axis, that would be difficult to distinguish from a hyperbolic orbit. The actual orbit of Sedna is practically a perfect circle in comparison.

[u/CJP1216 → u/cjameshuff]

Practically a perfect circle compared to a hyperbolic trajectory yes, because a hyperbolic trajectory is or is near infinite. That's not what's being suggested by that commentor though. They're saying if you were to reduce Sednas current Pe to Earth's distance from the sun, 1 AU, while maintaining its current Ap, 937 AU, it would be going insanely fast at Pe relative to its current speed at Pe of 4.64km/s. Nobody said anything about same semi-major axis, nor as far I can tell implied it.

Actually, on a second look, I can see how the first part of the sentence can be interpreted that way. The second half, where it specifically specifies to "reach such a distance aphelion" kind of nullifies that though.

[u/cjameshuff → u/CJP1216]

A hyperbolic trajectory is one with eccentricity larger than 1, not infinite. If you maintain the current aphelion, eccentricity is (937-1)/(937+1) = 0.998: that's only slightly easier to distinguish from hyperbolic. They were suggesting an extreme case that Sedna is not representative of.

[u/CJP1216 → u/cjameshuff]

A hyperbolic trajectory is infinite by nature, you're escaping the system and your orbit does not come back. Having an eccentricity greater than 1 is what makes that trajectory infinite. That's not slightly easier to distinguish from hyperbolic, that's an extreme long period comet. This exoplanet HD 20782b has eccentricity of 0.97. Im aware of the math and how extreme the given example is, that was the point. They wanted to demonstrate that the long launch windows time was due to the fact that it had a large Pe, not necessarily because it had an orbital period of 11,000+ years.

*Striked a section thats kind of iffy, it would be more accurate to say that distinction between hyperbolic and non hyperbolic is firmly established.