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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

#311

Post by shkkmo »

perl4ever wrote: post #246
CamperBob2 wrote: post #233

Earlier quoted context omitted.

One of the criteria for planethood is an assumption that the body clears its own orbit. Moons don't just come hurtling out of the cosmos; they either result from a collision of some other body with the planet, as with our Moon, or they're already close to the planet's orbit at the time they are captured.

>One of the criteria for planethood is an assumption that the body clears its own orbit. Is that so? "The generic definition of a centaur is a small body that orbits the Sun between Jupiter and Neptune and crosses the orbits of one or more of the giant planets" https://en.wikipedia.org/wiki/Centaur_(small_Solar_System_bo... There are tens of thousands, so perhaps the definition of a planet is even more abstruse than…

> Is that so?

Yes, it is. The definition of "clearing an orbit" isn't precisely defined, but it doesn't have to be since there appears to be a large natural gap in how much orbit clearing an planet does vs. a dward planet.

> A large body that meets the other criteria for a planet but has not cleared its neighbourhood is classified as a dwarf planet. That includes Pluto, whose orbit intersects with Neptune's orbit and shares its orbital neighbourhood with many Kuiper belt objects. The IAU's definition does not attach specific numbers or equations to this term, but all IAU-recognised planets have cleared their neighbourhoods to a much greater extent (by orders of magnitude) than any dwarf planet or candidate for dwarf planet.[0]

[0] https://en.m.wikipedia.org/wiki/Clearing_the_neighbourhood

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

#312

Post by 34679 »

ncmncm wrote: post #251
34679 wrote: post #121

>almost undoubtedly the largest Oort Cloud object ever discovered- almost in dwarf planet territory! Not a dwarf planet.

Thus, "almost". But big enough to be spherical. Or to eliminate multicellular life on Earth, if it hit us.

The headline does not contain "almost".

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

#313

Post by phkahler »

fouronnes3 wrote: post #113
Sharlin wrote: post #87

Earlier quoted context omitted.

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.

After Pathfinder someone from NASA wrote a book about their new "faster, better, cheaper" approach to missions. Usually you can't have all 3 but they managed to get lucky. That made it particularly amusing when the book and concept were getting popular as the next 2 missions were failing.

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

#314

Post by kbelder »

smegger001 wrote: post #256
peeters wrote: post #229

Earlier quoted context omitted.

Scott Manley had a recent video talking about the work involved in moving the Earth, that you might find interesting. Basically the most "plausible" approach might be to move the moon and use it to drag the Earth. Similarly the best way to move another large object might be to carefully move other objects small amounts to do precise gravity assists. https://youtu.be/5StYppuJ_lg

wouldn't that require a solution to the three body problem to make such precise gravity assists?

While we can't 'solve' the three body problem, we can make increasingly accurate estimations. Enough to usually get orbital mechanics right in the short-term.

For a setting where we were getting it right until we got it wrong, see Niven's "A World out of Time".

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

#315

Post by dancemethis »

c3534l wrote: post #52
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?

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

A variation of this worked well for Final Fantasy XIV.

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

#316

Post by andy_ppp »

blocked_again wrote: post #292
subroutine wrote: post #287

Earlier quoted context omitted.

Shoot a rocket into outer-space with a bunch of full human genomes (sequencing data), a backup of the internet, and a readme. The probability of a starship being within 5 lightyears of earth is likely zero. If there is one, it's probably because it's already on its way here.

This is under the assumption that advancee civilizations can travel only as fast as speed of light. There is also a possibility that there are advanced civilizations that jailbreaked the Universe/Reality and can be anywhere in seconds. Whether they give a shit about primitive civilizations like us who invented decent computers only like fifty years back is a different question altogether.

Wormholes are great for that, the issue would be getting a signal to reach anyone useful in time. We need to find out how subspace radio works…

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

#317

Post by lamontcg »

geenew wrote: post #239
lamontcg wrote: post #45

Earlier quoted context omitted.

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…

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.

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.

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

#318

Post by nwallin »

chronogram wrote: post #85
mcorning wrote: post #13

For reference 1 AU (Astronomical Unit) is about 150 million km. Saturn ranges from being about 7 to 11 AU away from Earth. Voyager 1 is 152 AU away. This object is excitingly close and will be fun to study.

How come our culture didn’t base astronomical units around base 10 of our current units?

Astronomers could reasonably well measure angles between objects in the night sky, and with some basic geometry, you can measure the relative distances between objects reasonably accurately. For instance, if you have a triangle ABC, and you know the angle ABC is 45 degrees, and the angle ACB is also 45 degrees, you know that the distance AB will be sqrt(2)/2 times the distance BC. If you have dozens of other points you want to know about, you can calculate the distances relative to BC as well. But what if you haven't the foggiest idea how many toises long BC is? (this was well before the metric system; toises was the unit of choice for Cassini) You either give units of toises for, for instance, the size of the Mars orbit with error bars of +/- 80%, or you give the size of the Mars orbit in terms of multiples of BC with error bars of +/- 5%.

Measuring the AU is fraught with errors of all sorts. For centuries it mostly consisted of exploiting tiny parallaxes on the Earth's surface between planetary bodies- for instance, Cassini and Richtie measured the parallax of Mars between Paris and French Guiana. But a small error propagates to a much, much larger error in the final result than relative distances between planetary bodies in AU distances. If your measurement of the parallax of Mars is off by one arcminute, your measurement is totally useless, but if your measurement of the angle to Mars is off by one arcminute, your distance to Mars in AUs is off by a few percent.

It wasn't until the 1960s when the JPL measured distances to Venus and Mars using radar that we were confident we had a good grasp on how long an AU was. But by that point, we had already measured the relative distances between the bodies in the solar system using the AU ruler relatively accurately for centuries.

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

#319

Post by avaldes »

lumost wrote: post #309
monkeycantype wrote: post #257

Earlier quoted context omitted.

how would we aerobreak it in mars's atmosphere into a decaying orbit, so instead of slamming into mars, it breaks up and rains down on mars? What can we tell about the composition - a solid rock or icy rubble?

The martian atmosphere will have a negligible impact on a 200km wide object. Tidal forces would likely shred the object and the surface of Mars if an aerobraking maneuver was attempted.

Shouldn't break by itself with Mars' tidal forces alone?

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

#320

Post by loa_in_ »

DiabloD3 wrote: post #249
bnjemian wrote: post #162

I say we catch that sucker, tow it into our neck of the woods as a second moon, and use it as a space port. Are there a million problems with this proposal? Yes. But would it be totally rad to do this? Also yes.

How are you going to deal with the imbalance in charge? It's likely that the to-be-moon has a very large charge differential between it and the Sun, but also likely between us and it.

That's true. In extreme cases it could really upset Earth's magnetosphere. And since we don't know we can't assume it's magnetically inert.
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