Another question for QI
You know all those questions on QI about how many moons does the earth have!
Earth has a mini-moon: a space rock close enough to be a near-Earth asteroid spotted this month orbiting our planet. The object, known as 2020 CD3, was reported by the International Astronomical Union’s Minor Planet Center, a small organisation that tracks asteroids and comets. It's most likely an asteroid that has been …
Oh freddled gruntbuggly,
Thy micturations are to me, (with big yawning)
As plurdled gabbleblotchits, in midsummer morning
On a lurgid bee,
That mordiously hath blurted out,
Its earted jurtles, grumbling
Into a rancid festering confectious organ squealer. [drowned out by moaning and screaming]
Now the jurpling slayjid agrocrustles,
Are slurping hagrilly up the axlegrurts,
And living glupules frart and stipulate,
Like jowling meated liverslime,
Groop, I implore thee, my foonting turlingdromes,
And hooptiously drangle me,
With crinkly bindlewurdles,mashurbitries.
Or else I shall rend thee in the gobberwarts with my blurglecruncheon,
See if I don't!
... the one with the poetry book in the pocket please.
"Space rocks visiting Earth like this are rare. Described as mini-moons, the only other time that one graced our planet (that we know about) was in 2006. A tiny asteroid, measuring a couple of meters in diameter and known as 2006 RH120 was also discovered by folks working at the Catalina Sky Survey."
Presumably it's ruddy hard to spot them though, particularly given they don't stay for long, so do we know how rare or not it is?
I did wonder about how they worked out what percentage of asteroids of certain sizes they'd found using the logic you use above.
They scan the skies for asteroids and compare the number of new ones they've found with the number of old ones they found again!
Given 2 is all we have found so far and they bugger off I think this may the wrong way to go about it but in a few hundred years we may get a useful data set.
That's not quite how it works. If you are doing "loops" then you are orbiting and "stable". What is may mean is it's orbiting, but the changes of gravity caused by the Moon (for example) wissing past will then perturbed it back out of orbit. Presumably the moon helped in the original capture.
AFAIK you'll only get one or two pass bys if a natural "capture" with a non stable orbit. Any real captures require something to slow it down (solar wind, perturbations in the planet, not likely at our size, or a moon/third body to disrupt the flyby).
>"Any real captures require something to slow it down"
How about a hastily put together SpaceX mission to give it a nudge? Considering the effort that goes into missions to study such objects, it would be nice to have one in a longer term stable - or at least somewhat predictable - local orbit for future science missions.
Not a very easy question to ask Google so I'll answer.
The asteroid has an oval orbit, with an apogee (highest point in the oval orbit) beyond the lunar orbital distance. This means given enough time at some point it will come into the moon's sphere of gravitional influence and be slung back out into interplationary space
"But could it be slung the other way and come down on someone's head ?"
Yes, technically it can. But ...
The Earth is *tiny* and the rest of the universe is damned *huge* so hitting the tiny, tiny Earth is far more unlikely than hitting the rest of the universe or even the littly bit of it that our Sun looks after.
True, millions of tons of dust, detritus, small rocks and bigger boulders *do* hit the Earth each and every year and every so often a quite large to bloody enormous one will find us but those things [apart from the QLTBE-types] do pretty much no harm at all.
A small, car-sized brick won't do much, either even should it suddenly decide to cuddle up to our little planet. Odds are it would break up to provide a few fireballs and pretty falling "stars" that would be seen over some Russian village.
They are *always* seen over Russia, which is probably all to the good.
Technically there is no such thing as a stable orbit even for just two bodies, when considered on long enough timescales.
Two objects (spherical and in a vacuum) orbiting each other will radiate energy as gravity waves. This will cause the orbits to shrink, and eventually the two objects will be one.
It's just that for small objects (e.g. the Sun and the Earth) the timescale required to radiate this amount of orbital energy is long enough that the life cycle of the objects happens first (Sun -> red giant -> planetary nova)!
And yes, the Moon is slowly moving away from the Earth. But that’s because it’s stealing rotational energy from the Earth by the use of tides.
"And yes, the Moon is slowly moving away from the Earth. "
Well, the Moon isn't one, she's more of a companion planet or, considering the I.A.U.'s recent unfair demotion of Pluto and the asinine "reasoning" behind that, a companion Dwarf Planet. Luna, the Moon, isn't "round", she's more ovoid [allegedly due to the gravity of a nearby object] and she sort of, kind of, slightly hasn't exactly totally cleared her orbit of large lumps. We now that latter because we live on one of the uncleared bits - well, many of us do, some of the time.
As Luna, the Moon, isn't "really" a moon, one should not expect her to behave as the other, littler [compared to their hosts] ones do.
Of course, the Earth is a slightly lumpy oblate near-spheroid that hasn't cleared her orbit [see the article for details] so the Earth isn't a planet, either. It's debatable that any object save Venus [maybe Mercury, too] *is* a planet.
Given a little bit of lead time we could do local science even with a temporarily captured object.
We have probes designed for asteroid encounters in deep space... I'm sure we have a spare one (it would have to be old enough that the primary mission of the version in space has finished) that we could pop onto a rocket and set up an intercept.
Does the Ceres-Vesta "Dawn" probe have a museum-quality twin sitting around spare? Could we power her up, plonk her on a rocket and zap her to this new moon of ours?
Hell, I'd volunteer to go on a Soyuz or ESA re-supply rocket without a return ticket, just for the "wheeeee" of it. I'm sure I can be remotely piloted by real geologists, chemists and other actual Scientists so I could do valuable work.
Anyone at NASA, ESA, JAXA or the Indian one reading this?
This thing has been parked up for 3 years and nobody noticed a 3m (approx) wide POS wafting about. I thought NASA was constantly tracking everything bigger than a small shit. And you would've thought Donald's Space Farce would have given it a poke. Obviously everyone has been in "don't mention aliens" mode up to now.
How do you know the old "Orange One" didn't decide to strap a TLA onto the thing to bomb Iran? That would be a handy excuse to say, "we didn't do it - Allah did!" Hee! Hee! Hee!
It is the perfect excuse - especially since they already worship a space rock every Hajj at Mecca, how could they lose! Hee! Hee! Hee!
As the post above stated, they *do* worship a rock that *did* survive entry [ *NOT* "re-entry" as it probably didn't start its life as a part of Earth] so it's possible this one might.
It depends on what it's made of and how we land it. Dropping it vertically, like a rock, would be best as this would give it least time to interact destructively with the airs of Earth and most opportunity to merge interactively with the less squishy bit. It wouldn't do much regional damage even so but it might damage the core of a city if it fell from its apogee.
The problem with that is The Rocket Equation. It takes effort to cancel orbital motions, as much effort as it takes to set them up and even a little rock weighs many tons. Effort means fuel and fuel must be lifted from Earth's surface to the moon.
Sending in the U.S. Armed Forces is probably cheaper.
"Commercially viable minerals" is probably the wrong one to measure.
Let's assume it's 3m in diameter and roughly spherical. This would make it 14.14m^3. Let's pretend it's made of pure platinum. This would make it around 300 tonnes of the stuff apparently. Worth of that is around $9bn. Average cost of a space shuttle mission was around $1.5bn.
I guess the problems with this are:
* It's orbiting way higher than the shuttle's range
* The shuttle or anything like it doesn't exist anymore
* It's almost certainly made of a less valuable material than platinum :D
Yeah but think of the value of the "bidding rights" from cities, ie the modern trend to waste millions bidding for an event, to be the one it is dropped upon from orbit.
Halifax : "We'll bid 1.2bn to drop it in Bradford."
Leeds : "We'll bid 2.3 bn if you drop it on Bradford."
Kirklees* : "We'll bid 14.3 bn if you drop it on us."
Sold, to the highest bidder.
*Not technically a city but ne'er mind.
I considered that, but as part of my “research” (loose sense of the word) I discovered we mine almost 200 tonnes of platinum a year, so probably not as big an adjustment as you might think. I was particularly surprised by that.
I suppose the other thing to consider is the cost of mining that on earth as a comparison to a shuttle-esque mission. Hard to put a number on it, but some stories suggest platinum mining is barely breaking even at the moment, so maybe the space shuttle to the non-existant platinum moon might be worth considering.
"You'd have to mine it from space, because it would never survive the atmospheric entry. Oh well!"
The whole point of this exercise is to use the space shuttle or similar. It's cargo bay was plenty big enough to hold the platinum moon (the moon is only 3m in diameter), but you're right it may well be a bit of a strain on the landing gear.
By this I take it you mean as soon as the orbit of this rock reaches the other end of what must be a hyperbolic orbit since it is going to escape the influence of our bigger rock.
One question I have is this, how does a mass in interplanetary space (or interstellar for that matter) get permanenty captured (ie enter a non hyperbolic orbit)? Since there is no friction in space other than if hitting some kind of atmosphere or the bigger mass that has captured the smaller one wouldn't this leave the 2 options of either joining the mass of the larger object permanently or being flung out on a hyperbolic orbit for somerthing like 99.999999% of the time?
"... how does a mass in interplanetary space (or interstellar for that matter) get permanenty captured ..."
Jupiter's moon, Io has one answer to that.
Tidal heating and momentum swapping during the flyby. Sort of like what is causing the Moon to fall upwards, away from the Earth but in reverse mode. Angular momentum can be transferred into or from the primary object's rotation, kinetic energy converted into heat.
It would take a large number of close approaches to drain the momentum and angular momentum from a passing rock but the physics isn't magic. The result may be magical and full of wonderment but the process is just the cosmos doing its thing.
Like a rainbow.
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