[Meerax]

Is this something we could plan and manage to launch an orbiter/lander to in time? Has anyone thought about the possibility of slapping something like a telescope on that and letting it beam back data and images from veryyyyy far out eventually?

[jessriedel]

If you launch your telescope on a spacecraft and get it to match speed with the dwarf planet (which is necessary for a soft landing), there's not much point in actually attaching it to the dwarf planet. That just blocks the view of half the sky.

Also, there will be nothing to see out there other than the dwarf planet itself.

[tonmoy]

Is that really true? If we manage to get a spacecraft get captured by the dwarf planet's gravity and orbit it, would that not be a lot less delta-V compared to if we made the spacecraft achieve the dwarf planet's orbit around the sun just by itself?

[jessriedel]

Yes, this is an aspect of orbital mechanics that people find unintuitive before they study it. You can't be captured by a planet's gravity alone. If you come in from infinity (i.e., not already captured) you will escape to infinity (remain not captured). The basic idea can be seen from the fact that gravitational dynamics are time-reversible, so if gravity could capture you like this you could also start in orbit around a planet and spontaneously be ejected.

Now, something like this can work if you use an irreversible interaction like aerobreaking, but this dwarf planet has negligible atmosphere. You could also use the dwarf planet for a gravitational assist (basically bouncing off it like a billiard ball), but I think gravitational assists from the other planets are almost always more convenient and effective.

[azernik]

It can reduce the delta-V requirements, though - by the same principles as a gravity assist, a capture burn (especially into a loosely-bound planet-centric orbit) often takes less work than burning into the equivalent heliocentric orbit on your own.

[JumpCrisscross]

> by the same principles as a gravity assist, a capture burn

Note to the audience: these mechanisms don’t violate the conservation of energy because you aren’t tapping the object’s gravitational energy per se but instead its orbital energy around the sun. Put another way, you can’t do a gravity assist or capture burn in any direction.

[azernik]

The usual way I explain it is as a transfer of kinetic energy and momentum from the large body to the small one. The interaction is through gravity, rather than the mix of electrostatic, degeneracy, and strong/weak forces involved in collisions; but the equations are more or less the same.

(Usually textbooks use a baseball bouncing off a semi truck to illustrate.)

[beckingz]

Right! The Oberth effect for a smaller body is not as large as it would be for earth, but would still be non-zero.

[lmilcin]

"Non-zero" is the key word here.

Oberth effect from fast flyby of a body with low gravity would be negligible.

[jessriedel]

Ok, good point. Thanks.

[azernik]

Still definitely not worth it for something so small, though!

[tmhrtly]

What if we crash landed into it? That would probably tick the irreversible box. Clearly engineering difficulties quite high though!

[Sharlin]

This is often jocularly called lithobraking and is typically not advisable.

[mianas]

I came here to reply to the parent comment's remark about "irreversible interaction like aerobreaking, but this dwarf planet has negligible atmosphere." by mentioning lithobraking because it's been consuming my thoughts for the past couple of months.

Like, imagine a collapsible rod about a kilometer long sticking off the end of a space probe, lined up so it hits the surface as close to perpendicular as possible, each segment made of appropriate material for its impact speed. (I think once you go past the speed of sound in a material, you can't transfer any more force)

With the far end of the rod, which impacts first and with the most force probably vaporizing/creating a crater on the surface (useful to align the rest of the rod), and later sections crumpling in on themselves predictably, like a highway crash barrier or car hood. With a certain max amount of Acceleration, Jerk, Snap, etc... that the probe can survive.

I would very much like someone to explain why decelerating a spacecraft like this is infeasible/inefficient so I can stop thinking about it. Failing that, I wish to devote the next few years of my life to jamming a massive spear into the moon.

[fouronnes3]

> not advisable

Unless you're NASA landing a probe on Mars in 1997.

[ehsanu1]

It's a cool idea, but seems super sci-fi. Might need some wonder materials to make it feasible, even then that would be a really big crumple zone. Or flubber. Another crazy idea: latch on to the planet from the side, like a skateboarder hitching a ride by hanging on to a truck. Again, wonder materials required.

[azernik]

NASA and the Soviets didn't need any wonder materials, just airbags. (Though they did a lot of braking first - either with the atmosphere for NASA at Mars, or with thrusters for the Soviets at the Moon.)

[gifnamething]

That crash still needs to absorb the same amount of speed that was just defined as too much to expel in orbit

[shkkmo]

> You can't be captured by a planet's gravity alone

Technically, this isn't completely true. There are gravity assist techniques that will allow you to dump speed by essentially adding your momentum to the object you are trying to orbit. The is basically an anti-slingshot manuever.

In practice, I believe the range of scenarios when this is possible with a dwarf planet is so small as to be practically useless.

[Armisael16]

In a two-body system it doesn’t matter what you do; gravity is a conservative force so conservation of energy demand that you leave the body’s SoI at the same speed you entered it (in the body’s frame of reference).

You can lose speed or alter course relative to another body in a single encounter, and those changes can reduce speed in future encounters, but if you’re on an escape trajectory heading in you stay in one (without forces beside two-body gravity, which is a pretty safe assumption 11 AU out of Saturn doesn’t come close).

[shkkmo]

> In a two-body system it doesn’t matter what you do;

Two-body systems do not exist in reality.

Energy is also conserved in 3 body problems. When you utilize the slingshot effect, some of the energy of the orbit of the body you are swinging around orbiting is transfered to you. The transfer of this energy does not depend on the closeness of the sun, but rather on how deeply you descend into the gravity well of the object you are slingshotting around.

> which is a pretty safe assumption 11 AU out of Saturn doesn’t come close

No, it really isn't. The "safeness" of the assumption entirely depends on your margin for error. The existence of the naturally captured saturnian satellites clearly indicates that you are simply wrong about the relevant margins for error.

[prince781]

> gravitational dynamics are time-reversible, so if gravity could capture you like this you could also start in orbit around a planet and spontaneously be ejected.

I don't have a strong background in physics, and perhaps this is splitting hairs, but is this true if we consider gravitational radiation? Over a very long time a body's orbital energy will be lost to gravitational waves.

[lmilcin]

It would be like saying all the school children exercises and train timetables are invalid because they don't take into account relativistic effects that obviously are still present at 60mph.

[a1369209993]

Technically? Yes! Incoming gravitational radiation of precisely the correct shape will in fact un-decay a orbit under exactly the same (modulo appropiate symmetries) circumstances as a orbit would decay by emitting (the reverse of) that radiation. (The same applies to thermal radiation cooling things off - see Liouville's Theorem.)

For practical purposes, that'll never happen, but for practical purposes gravitation radiation doesn't matter anyway.

[himinlomax]

Over a very long time, we are all very dead. From what I understand, the loss in gravitational energy would be so tiny, the length of time required for it to eventually matter in any way would be way beyond the lifespan of the sun. So it's only a finite duration if you have infinite time, which you don't.

[CamperBob2]

That's pretty cool. It's wildly counterintuitive, but if it weren't the case, the planets would be orbited by lots of captured asteroids and debris, instead of/in addition to being covered in craters. The only explanation for why that doesn't happen is that it can't happen.

[shkkmo]

The presence of natural satellites indicates this can indeed happen. It just requires a pretty unlikely orbital configuration.

[stickfigure]

Or an impact:

https://en.wikipedia.org/wiki/Giant-impact_hypothesis

[dragonwriter]

> The presence of natural satellites indicates this can indeed happen

No, it doesn't, because natural satellites are generally not captured, and for those that are captured, the process involves interactions with other bodies.

[CamperBob2]

No, it doesn't. No (rocky) planet has more satellites than craters, but every planet's gravitational field is larger than its surface.

[isoprophlex]

It's a dwarf planet of ~ 200 km diameter. The thing has a miniscule gravity well, it won't matter much compared to launching from earth and matching orbits with it, i think...

[azernik]

For comparison, that's about 10% of the Moon's diameter, i.e. 0.1% of its volume. (The mass ratios are probably within that 0.1% ballpark, but can't tell for sure until we know more about its composition.)

[eb0la]

IMHO beign able to spot something with this size at this distance is really awesome.

[azernik]

Interestingly, the images came from the Dark Energy Survey [1], which for entirely different different reasons is running a very sensitive and high-resolution scan of the sky in visible and near-infrared. This just happened to show up in a frame where they were looking for distant galaxies and events, and the Minor Planets Center noticed the thing.

[1] https://en.wikipedia.org/wiki/Dark_Energy_Survey

[cwkoss]

Could a probe have a long tethered anchor, so as it does it's flyby the friction of the anchor dragging the surface would shed more delta-V than the weight of the system (in comparison to just loading up on more propellant)?

[Teever]

> there's not much point in actually attaching it to the dwarf planet.

I've been thinking that attaching a sabatier reactor to a probe and sending it to land on an extra solar body such as Oumuamua that contains the ingredients that the sabatier needs to produce fuel would be a great way to get a probe that sends signals back to Earth well after a nuclear battery has died.

[vmception]

and frozen aliens

[seaman1921]

perhaps the sun's heat exposes them :)

[egman_ekki]

...that must be the delivery of ufoporno I ordered in good'ol devonian times :)

[bewaretheirs]

Just launch a deep-space telescope; it would be easier.

Soft-landing the telescope on an airless body would be harder (in delta-V terms) than just launching it into an equivalent solar orbit. And the body would block about half your view of the sky at any one time.

[jbay808]

Could you get a nice gravity boost away from the sun by just following it for as long as possible?

[lamontcg]

No, that's not how gravity boosts work. If you match speeds with an object you actually get zero boost.

The point of a gravity boost is to come in pretty hot (relative to the body you're boosting off of) and then go out pretty hot in a different direction. So you take your relative velocity vector at the point of the encounter and twist it around. By doing that you change your orbital energy around your central body (the sun) by a lot, and the other object will lose a similar amount to keep the bookkeeping equal.

If you have zero relative velocity compared to the thing you want a gravity assist off of you can't get an assist. It isn't like drafting a semi.

[stnmtn]

Interesting, do you mind explaining how the "other object will lose a similar amount"? I find orbital mechaics fascinating and understand the concept of a slingshot, but I can intuitively understand how if we launched a rocket and slingshotted it around the moon, the moon would be affected by that

[geenew]

Could there be some energy advantage to being in orbit around it? I'm thinking of a scenario where you spend a large amount of energy once get into orbit around the object, but then gain a small amount of energy continuously through something like tidal forces.

[lamontcg]

Everything else is going to be small and average out over time. And if you manage to pick up a bit of energy orbiting a tiny object you'll quickly just get ejected at its (small) escape velocity. Whatever that gives you, it won't be worth the cost of matching orbits to start with. Better to come in hot and slingshot.

Solar wind / radiation pressure is probably the next best free ride since that adds up over time continuously and is everywhere.

[jstanley]

I think the point is that in order to follow it, you need to (at some point in time) be at the same place and with the same velocity. Then you'll follow it.

But the energy required to do that is almost the same as what it would be if the dwarf planet wasn't there. You could get onto exactly the same orbit for roughly the same amount of energy, and if you relax the requirement that there be a dwarf planet nearby, you can choose superior orbits.

[0-_-0]

I think it should provide a much stronger slingshot velocity boost than any other planet, however getting to 11AU first is not easy.

https://en.wikipedia.org/wiki/Gravity_assist

[btilly]

For the best gravity assist you want to have a large delta V, and you want to come in on a hyperbolic orbit that causes you to turn by 90 degrees.

This object has all of the delta V that you could want, but for an object of that mass, the hyperbolic orbit would require going through the planetoid which you can't do. And if it was dense enough that you could (for example a miniature black hole), the tidal forces during the turn would be insane.

So no, this object cannot give a decent slingshot.

[simonh]

The magnitude of the slingshot boost increases with the mass of the planetary body. This thing is smaller than any of the planets so you’d get a much smaller boost. The best planet for slingshotting from is Jupiter because it’s the most massive.

[_Microft]

The easiest way to think about this is as perfectly elastic collision between the spacecraft and the planet (mediated by gravity, but this is an unnecessary detail already).

[elihu]

It's probably more interesting to study the object itself.

I assume its orbital period is long enough that it won't be back near the central solar system for a very long time. But similar objects could have interesting uses.

One thought experiment is to consider what it would take to be able to live on such an object, perhaps even a rogue planet just floating between the stars.

It would be very cold. Presumably you'd be reliant on nuclear fission or fusion for power, so you'd need a significant fuel supply that could effectively last indefinitely. And you'd want to have a ready supply of all the basic elements you need. Which seems more realistic the bigger the object is. Like, an Earth or Mars-sized rogue planet might be ideal.

[anfilt]

Like till it gets closer we dont even know if it would be suitable to put something like that on it.

Although it does seem like interesting idea.

However, we have sent probes much further than this object (aka the voyager missions).

So it would mainly be useful for studying this object. So a telescope would be less than ideal since we could always in theory deploy a telescope much deeper into space if we wanted.

[floatrock]

Interestingly, the voyager missions were also timed-events -- they were launched when they were because JPL realized it was a 1-in-175-year alignment of the outer planets that made it feasible to launch just a few crafts to visit the outer planets all in one go: https://en.wikipedia.org/wiki/Grand_Tour_program

[f6v]

AFAIK many launches are timed to make the flight shorter. Although not on 1 in 175 years, but shorter windows.

[mikeytown2]

Landing a telescope on it would only make sense if orbits around it are highly unstable (like our moon) and if the dwarf planet was geothermally active so energy on the surface would be "easy" to extract (which comes with it's own set of headaches). Orbiting it with a "big for space probes" camera would most likely give us more interesting data.

Using the plant as a Coronagraph if orbiting far out is another interesting idea, but using a near earth astroid would be a better idea as the telescope could be powered by solar panels they.

[mrandish]

> slapping something like a telescope on that and letting it beam back data and images from veryyyyy far out eventually?

While this object will eventually orbit pretty far away in a solar system context, I suspect that additional distance may not be vast enough to make a meaningful improvement in observations of targets at interstellar distances.

I'd love to learn if I'm incorrect but I've always assumed for interstellar observation, larger sensors and more sensors has better ROI than a more distant sensor, at least short of some substantial fraction of a light year. If we're going to dedicate a 100 ton Starship payload to interstellar observing I imagine going much farther out than the Moon's shadow may not be a good trade (eg fuel mass vs payload mass).

[z3t4]

Too far out from the sun and it wouldn't be able to re-charge using solar panels. Could put some kind of nuclear power plant on it though. And as others has pointed out, you would need to match the speed, so you could just as well use that power plus gravity assists to get far out. Landing on such a body would be really interesting though.

[ianai]

Probably the reason to orbit such a planet would be to help comms from a ground station on it.

11 AU though seems like quite the stretch right now but maybe if there were a fleet of Spacex Starships in operation…

[c3534l]

Apparently no one likes this idea. Here's mine: we nuke the planet and collect its smitherines for SCIENCE!

[015a]

Let's send some boosters out there, redirect it to earth, and make a second moon. Come on people, what ever happened to doing shit cause its fuckin' rad, do you know how cool another moon would be?!

[f6v]

Let’s just blow the moon up and give rise to 7 new genetically engineered races, man-fishes, and dwarves.

[beckingz]

If it worked in SevenEves I don't see why not?

[hirundo]

Constructive interference from multiple tidal waves could flood huge coastal areas, killing or displacing millions. Uncool.

[015a]

Then again, global warming is going to flood huge coastal areas, killing or displacing millions, which is a pretty uncool thing we're doing to ourselves, so maybe Second Moon will counter-act that? There's literally no way of knowing until we try. And worst case scenario, we ruin a bunch of earth and we've got a second moon to move to. Its a win-win.

[jazzyjackson]

Put it in orbit at a 90 degree angle from the moon with Earth as the center and you can cause destructive interference and lower the tides :)

[dylan604]

Or very cool if you're an evil villain in a movie/comic. Give me one milllllion dollars, or I will bring in a second moon!

[Koshkin]

Bringing a large celestial body close to Earth would be just as smart as trying to let the aliens know that we are here. (The humanity may not be able to survive either one.)

[dancemethis]

A variation of this worked well for Final Fantasy XIV.