Astrophysics & Space Exploration

[E Pericoloso Sporgersi]

http://www.latimes.com/news/science/la- ... 1561.story

Just a wild thought:

Suppose Eris originally occupied Mercury's orbit. Then Mercury, an extrasolar wandering planet, collided head-on with Eris and kicked it to its current transplutonian orbit. The collision slowed Mercury enough to make it adopt a close solar orbit, replacing Eris. Both Eris and Mercury lost their less dense outer layers in the collision, which explains why they're unexpectedly heavy for their size. The more eccentric asteroids might be collision debris. Just think of all the impact craters throughout the solar system and the asteroid-shaped Phobos and Deimos.

Mercury, during its cometary plunge into the solar system, also disturbed Pluto's orbit, making it more inclined and much more elliptical. This also bent Mercury's trajectory to be more congruent with the ecliptic plane and aimed it almost straight at Eris.

Lastly, in passing, Mercury's influence inclined the Moon's orbit, causing the Earth's axis to shift accordingly, while Earth's reciprocal gravity aimed Mercury exactly at Eris.

Could Eris now be responsible for sending some comets to the inner system?

So in aiming Mercury towards Eris, Pluto is the guilty perpetrator and deserved to be demoted. Right?

Okay, okay, I said it's wild, didn't I? But ... er ... Voralfred, what do you think, does it agree with gravitational physics?

[voralfred]

http://www.latimes.com/news/science/la- ... 1561.story

Just a wild thought:

Suppose Eris originally occupied Mercury's orbit. Then Mercury, an extrasolar wandering planet, collided head-on with Eris and kicked it to its current transplutonian orbit. The collision slowed Mercury enough to make it adopt a close solar orbit, replacing Eris. Both Eris and Mercury lost their less dense outer layers in the collision, which explains why they're unexpectedly heavy for their size. The more eccentric asteroids might be collision debris. Just think of all the impact craters throughout the solar system and the asteroid-shaped Phobos and Deimos.

Mercury, during its cometary plunge into the solar system, also disturbed Pluto's orbit, making it more inclined and much more elliptical. This also bent Mercury's trajectory to be more congruent with the ecliptic plane and aimed it almost straight at Eris.

Lastly, in passing, Mercury's influence inclined the Moon's orbit, causing the Earth's axis to shift accordingly, while Earth's reciprocal gravity aimed Mercury exactly at Eris.

Could Eris now be responsible for sending some comets to the inner system?

So in aiming Mercury towards Eris, Pluto is the guilty perpetrator and deserved to be demoted. Right?

Okay, okay, I said it's wild, didn't I? But ... er ... Voralfred, what do you think, does it agree with gravitational physics?

Well, even if Mercury was originally displaced by some other object from a far orbit to a cometary plunge towards the sun (this part is quite possible) it would need a very, very precise aiming to just replace another planet in close orbit, and send it so far. Two problems: why would Mercury get an almost circular orbit, though after many, many revolutions (about 4 per earth year) it might just be due to the influence of nearby palnets. But then, even if Eris is sent far away on a very elliptical orbit, larginally possible what would make it circular once it gets far away ? For that you have to add energy, and in an extremely precise way, otherwise the trajectory would remain very, very elliptic. Not likely. I don't really see the point of your theory of permuting Eris and Mercury... Mercury is heavy because light elements evaporated. All these gravitational coincidences jsut to expalin Eris mass? Whatever collision stripped it of light elements most probably happened "on site".

[E Pericoloso Sporgersi]

... But then, even if Eris is sent far away on a very elliptical orbit, marginally possible, what would make it circular once it gets far away ? For that you have to add energy, and in an extremely precise way, ...

Not necessarily. If the collision imparts too much energy to Eris, namely solar escape velocity, it would have to have a vector change and lose some energy. One or two outer giants, say Jupiter and Uranus could take care of most of that with a gravity assist. A last minor collision (vaporising a comet-like object) and/or a near-collision in the Kuiper Belt would make the final slowing and circularising adjustment, though Eris still has a very elliptical orbit with 0.441 eccentricity.

Of course the probability of all these required events happening just so, keeps it from being more than a thought experiment.

But it would look nice in a Science Fiction story.

A billion years ago, the Thrintun maintained a base on the Moon to watch over the Earth's Bandersnatch population. The Tnuctipun, not daring to get close, used an interstellar rogue planet (its remnant is now Mercury) as a kinetic weapon to destroy that Slaver base. But they missed and Mercury hit Eris instead, thereby coming to an almost dead stop. The vaporised volatiles of the rogue planet were captured by Venus, causing its run-away greenhouse problem. Between then and now, Mercury didn't have enough time to get its orbit tidally locked to the sun. Eris was kicked off into an elliptical orbit in the Kuiper Belt's scattered disc.

And who knows, there still might be a capsule in a Slaver Stasis Field on the Moon ...

[voralfred]

Well, as an idea for a SF story, that looks good.
But the odds against it are pretty large. Also, to expel Eris (which is heavier than Mercury) you'd need Mercury to have a speed somewhat larger than solar escape velocity, meaning it must come from outside the solar system (or get accelerated en route) .And in case of a physical collision (in order to lose the volatile elements) one loses a lot of energy. Eris won't get enough. For expulson one needs an "elastic" scattering, just by the time-dependent gravitational field of the incoming Mercury that would trnasfers energy to Eris. If there is a collision than you'd need Mercury to have a speed orders of magnitude higher than solar escape velocity. This would definitely mean extra-solar origin...

[E Pericoloso Sporgersi]

... Eris (which is heavier than Mercury) ...

The Wikipedia claims that

• Eris == 0.0028 Earths
  Mercury == 0.055 Earths

In other words, Mercury is almost 20 times more massive than Eris!

In my little story, it's not a question of Eris not getting enough energy, but of how it managed to stop the extrasolar rogue planet (arriving with more than escape velocity) without getting flattened and spread out over Mercury's leading hemisphere.

P.S. Before I forget, for my little story I borrowed heavily from Larry Niven's Known Space.

[E Pericoloso Sporgersi]

The Wikipedia page about Eris shows a repeated animated image of Eris. Three frames were shot with one hour intervals (Eris is moving downwards).

In the second frame you can see the business end of a ship's fusion drive. The next frame was taken an hour later, by which time the ship had left the field of view. Look for the blinking white light halfway between Eris and the picture's upper edge.

And if you study the shots long enough, you'll notice more white fusion drives. Lots of traffic in that neighbourhood.

[voralfred]

... Eris (which is heavier than Mercury) ...

The Wikipedia claims that

• Eris == 0.0028 Earths
  Mercury == 0.055 Earths

In other words, Mercury is almost 20 times more massive than Eris!

In my little story, it's not a question of Eris not getting enough energy, but of how it managed to stop the extrasolar rogue planet (arriving with more than escape velocity) without getting flattened and spread out over Mercury's leading hemisphere.

P.S. Before I forget, for my little story I borrowed heavily from Larry Niven's Known Space.

Sorry, I read the link you posted too fast.. Eris is 27% heavier than Pluto, not Mercury, of course!

Assuming the rogue planet (Mercury) was not extra-solar, but just was knocked out of a far orbit to a cometary one that brings it close to the Sun (by some collision up there), it might well expel Eris by gravitational force (not necessarily getting so close as to have an actual collision). That would slow Mercury a bit more, and then allow interaction from Venus and Earth slowly make its elliptical orbit closer to circular, over a few eons; not totally absurd. Eris could get expelled at a rather high speed, up to twice the incoming speed of Mercury though probably less than that. Still enough to reach near escape velocity. But on a very ellptical orbit (eccentricity almost equal to 1). What I really can't see is how to reduce ti to such a samll value as 0.441 which corresponds to a ratio of short to long axis almost equal to 0.9 !

[MidasKnight]

Why is this in the Tap Room?

[E Pericoloso Sporgersi]

Why is this in the Tap Room?

Because we started with a dwarf planet and we'll end up with meatballs?

[laurie]

Why is this in the Tap Room?

Because we started with a dwarf planet and we'll end up with meatballs?

I moved it back to the Pellegrino forum, which seems the best home for the topic.