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Started by emorobot on May 21, 2018 5:56:43 PM
FURY as asteroid found to be IMMIGRANT from FOREIGN STAR

Namouni said the asteroid is unlikely to be the solar system’s only immigrant. The computer modelling reveals that asteroids that had been captured by Jupiter but then broke free from the planet’s gravitational pull would now be orbiting the sun on a path perpendicular to the plane of the solar system.

https://www.theguardian.com/science/2018/may/21/re
trograde-asteroid-is-interstellar-immigrant-scientists-say


So let's get this straight: There may be many, many more ILLEGALS in our solar system! Ming The Merciless, stellar dictator and lovable bad boy of politics, said: "Let's get tough and BUILD THAT WALL! We know these illegal aliens are only out to shag Earth girls!"

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Hilary - 22 May 2018 12:35:45 (#1 of 31)

The computer modelling reveals that asteroids that had been captured by Jupiter but then broke free from the planet’s gravitational pull would now be orbiting the sun on a path perpendicular to the plane of the solar system.

Why would that be? And at what angle to the ecliptic is ‘Oumuamua orbiting?

coshipi - 22 May 2018 12:40:25 (#2 of 31)

Why would that be?

Why indeed. Random, yes; perpendicular to the ecliptic, no reason at all. Hopefully that's a journalist misunderstanding something someone knowledgeable has said; if it's someone who's supposed to be knowledgeable who's said it, then they're not as knowledgeable as they're supposed to be.

Possibly an all cows are animals, therefore all animals are cows kind of error on the part of the journalist.

And at what angle to the ecliptic is ‘Oumuamua orbiting?

I don't know, but a previous article (possibly no more authoritative than this one) showed it at a steep angle to the ecliptic, but not perpendicular.

coshipi - 22 May 2018 12:42:57 (#3 of 31)

(And of course if it's actually perpendicular, then retrograde is nonsense...

Hilary - 22 May 2018 12:46:21 (#4 of 31)

orthograde?

coshipi - 22 May 2018 12:51:35 (#5 of 31)

8~)

Nice word. But I don't think it is perpendicular at all. That would be a remarkable coincidence. So it may well be retrograde.

Of course non-immigrants can end up retrograde as a result of a close encounter with a planet - and well out of the plane of the ecliptic, too, possibly even perpendicular.

The only way to know something is extrasolar is if its velocity is too high - that is, if it's in a hyperbolic orbit.

bossab2 - 22 May 2018 12:53:08 (#6 of 31)

head hurts

TheExcession - 22 May 2018 12:57:16 (#7 of 31)

#6 Things wot came from the solar system all orbit in the same direction because they formed out of spinning disc. Thing wot came from elsewhere can be going at all sorts of crazy angles and speeds having been flung out of their starting systems.

coshipi - 22 May 2018 13:00:46 (#8 of 31)

#7 Basically, yes - but things wot came from the Solar System can end up at crazy angles or going in the opposite direction, by having an encounter with a planet. They can also acquire fairly crazy speeds that way, including getting flung clean out of the Solar System. But there is a limit to how crazy a speed can be acquired that way.

bossab2 - 22 May 2018 13:02:39 (#9 of 31)

A Chaotic Solar System.

Hilary - 22 May 2018 13:08:17 (#10 of 31)

Any 3-body system can be chaotic, can't it? (just assuming Newtonian dynamics)

coshipi - 22 May 2018 13:08:27 (#11 of 31)

Well - a certain amount of chaos in a generally very well-behaved system. The major planets' orbits have been largely stable for a very long time, and even most of the larger asteroids' orbits are pretty stable.

Hilary - 22 May 2018 13:13:15 (#12 of 31)

One thing I hadn't realised until recently, when I read a very interesting piece by John Baez, is that in Newtonian dynamics a five-body system can result in one of the bodies attaining infinite velocity in finite time.

I can't find the Baez article now but here's one by John Barrow.

https://plus.maths.org/content/outer-space-twos-company-threes-crowd

coshipi - 22 May 2018 13:16:48 (#13 of 31)

a five-body system can result in one of the bodies attaining infinite velocity in finite time

I think the bodies have to be point masses for that to work - if the bodies are realistic, spherical objects with non-zero diameters, they'd collide instead. (It being ever closer encounters, repeated at ever-decreasing intervals, that generate high velocities.)

FleurDuMal - 22 May 2018 13:24:49 (#14 of 31)

#6 Things wot came from the solar system all orbit in the same direction because they formed out of spinning disc. Thing wot came from elsewhere can be going at all sorts of crazy angles and speeds having been flung out of their starting systems.

Ah, now I get it.

Hilary - 22 May 2018 13:28:42 (#15 of 31)

Here's a more detailed expository article. AFAICS it does indeed assume point particles.

http://www.ams.org/notices/199505/saari-2.pdf

demoninatutu - 22 May 2018 13:32:43 (#16 of 31)

at what angle to the ecliptic is ‘Oumuamua orbiting?

Oumuamua isn't orbiting our sun, it came in perpendicularly and has already been flung out again. It's not the same thing as asteroid 2015 BZ509 (the subject of this article) which is orbiting in plane (AFAICS) but backwards.

Hilary - 22 May 2018 13:58:58 (#17 of 31)

Ah, thanks, I speed read the article and missed that.

It would be very surprising if the new interloping asteroid came in in exactly the plane of the ecliptic. What are the chances of that?

coshipi - 22 May 2018 14:25:32 (#18 of 31)

What are the chances of that?

Depends how precise you want the alignment to be. The major planets don't orbit in exactly the same plane anyway, of course.

Being exactly perpendicular to the ecliptic is more likely, but still not very likely - again, depending how precise you want it to be.

Oumuamua isn't orbiting our sun

Well - it's in a hyperbolic orbit, not an elliptical one, so it's a once-only visitor.

johnnythesailor - 22 May 2018 14:42:50 (#19 of 31)

Poor Uranus orbits on it's arse.

AppleCatcher - 22 May 2018 15:24:35 (#20 of 31)

It also exhibits (like Venus) retrograde rotation, which is weird; they’re the only two planets that don’t rotate counterclockwise when seen from above the sun’s and earth’s North poles. Orbits are all counterclockwise seen from the same viewpoint.

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