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A dwarf planet coming within 11 AU of the sun over the next 10 years

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Re: A dwarf planet coming within 11 AU of the sun over the next 10 years

#111

Post by dragonwriter »

shkkmo wrote: post #76
CamperBob2 wrote: post #66

Earlier quoted context omitted.

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.

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

> 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.

Re: A dwarf planet coming within 11 AU of the sun over the next 10 years

#112

Post by [deleted] »

jessriedel wrote: post #53
tonmoy wrote: post #38

Earlier quoted context omitted.

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?

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 aro…

[deleted]

Re: A dwarf planet coming within 11 AU of the sun over the next 10 years

#113

Post by fouronnes3 »

Sharlin wrote: post #87
fouronnes3 wrote: post #62

Earlier quoted context omitted.

> not advisable Unless you're NASA landing a probe on Mars in 1997.

Seriously, the tandem failures of the Mars Polar Lander and Mars Climate Observer missions were probably something NASA as an organization needed at the time. A reminder that Space Is Hard, and you can only pick two of "faster", "better", and "cheaper". Since then, NASA's Mars program has grown in both scope and ambition, yet remarkably has had zero loss-of-mission failures during that whole time!

I was referring to the successful landing of Pathfinder but yeah... Space is Hard and NASA is good at it are both very true.

Re: A dwarf planet coming within 11 AU of the sun over the next 10 years

#114

Post by ianai »

z3t4 wrote: post #106
Meerax wrote: post #23

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?

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.

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…

Re: A dwarf planet coming within 11 AU of the sun over the next 10 years

#115

Post by messe »

thoughtsimple wrote: post #109
messe wrote: post #49

Earlier quoted context omitted.

Somewhat unintuitively, thanks to the Oberth effect, it can be easier to reach escape velocity closer to an object, (Humorously portrayed in https://xkcd.com/1242 ). Aside: if you are looking to learn more, I cannot recommend Kerbal Space Program enough.

I think you meant: https://xkcd.com/1244/

Whoops. Yep, that’s the one.

Maybe I’ll be vindicated when it turns out the planetoid is made out of grey goo.

Re: A dwarf planet coming within 11 AU of the sun over the next 10 years

#116

Post by perl4ever »

dragonwriter wrote: post #111
shkkmo wrote: post #76

Earlier quoted context omitted.

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

> 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.

The first hit when I search "planets capturing moons" says natural satellites generally are captured.

"Most satellites of the outer solar system didn’t form with their host planets"

https://astronomy.com/news/2016/12/captured-moons-of-the-gia...

Even Triton, which is the size of a planet and in an almost circular orbit, is thought to be captured, the last I heard.

Re: A dwarf planet coming within 11 AU of the sun over the next 10 years

#117

Post by beckingz »

azernik wrote: post #70
jessriedel wrote: post #53

Earlier quoted context omitted.

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 aro…

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.

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

Re: A dwarf planet coming within 11 AU of the sun over the next 10 years

#118

Post by jakeinspace »

Denvercoder9 wrote: post #99
jakeinspace wrote: post #88

Earlier quoted context omitted.

I believe the 1.2B km was referencing mean orbital distance from the sun, which would be 8 AU, and therefore 7 AU from earth on closest approach.

No. Saturn's perihelion (closest distance to the Sun) is 1.35B km (9.0 AU), its aphelion (furthest distance) is 1.51B km (10.1 AU), and its mean distance is 1.43B km (9.6 AU). Thus, at closest approach Saturn is 8 AU from Earth (since Earth orbits at an almost-constant 1 AU from the Sun).

After checking Wikipedia, you are correct.

Re: A dwarf planet coming within 11 AU of the sun over the next 10 years

#119

Post by beckingz »

f6v wrote: post #68
015a wrote: post #56

Earlier quoted context omitted.

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?!

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

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

Re: A dwarf planet coming within 11 AU of the sun over the next 10 years

#120

Post by perl4ever »

messe wrote: post #14
jessriedel wrote: post #9

Earlier quoted context omitted.

New Horizons took a nearly straight shot to Pluto (just stopping by Jupiter on the way for a gravity assist). That trip took 9 years to travel 40 AU (not at constant speed, of courses, since it's constantly being drawn toward the Sun). This dwarf planet makes its closest approach at 10 AU, so you could do a fly by in less than 3 years if you wanted to pay for it. However, the science return from a flyby would be limi…

Getting into orbit would be rather difficult, as the probe would have have to match the planets velocity at perihelion. My instinct says it’s probably just on the edge of doable (although I’m not sure on which side), but I haven’t crunched the numbers. It would almost certainly need to be launched on a Delta-IV or Falcon Heavy class vehicle. EDIT: s/perigee/perihelion. I could say periapse and be neutral, but perihel…

In a few years, can't we look forward to SpaceX making it routine to refuel in orbit? If we assume that's feasible, I wonder what sort of missions it would enable, other than human spaceflight.
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