View Full Version : Astronomical Puzzle

tony draper
27th Jan 2015, 22:13
Report of a Asteroid passing close to Earth, the beast was about 300 meters across.
A Huge Asteroid Flew Past Earth Today, And It Has Its Own Moon | IFLScience (http://www.iflscience.com/space/asteroid-flew-past-earth-today-and-it-has-moon)
Now the puzzle, how come the body is so spherical?,surely a 300 meter rock would not generate enough of a gravitational whelt to pull itself itself a spherical shape.?
Am I the only one who notices these anomalies?, Draper gazes as from mountain tops whilst the rest of humanity gropes in the dark.

27th Jan 2015, 22:35

We are as the beasts that perish while your gaze is fixed on the stars. Nevertheless I did wonder about the same thing and have a couple of possible explanations. I'll wait for others before I reveal my ignorance.

After an excellent landing etc...

tony draper
27th Jan 2015, 22:47
Well heavenly bodies planets large asteroids ect adopt a spherical shape because it is the smallest volume a given mass can occupy,gravity obliges them thus because every particle in said mass is trying to fall toward the center due to gravitational pull,if they started cube shaped the corners would be pulled in and the resulting smaller corners would be pulled in and eventually we have a round body.
Many smaller astronomical bodies do not have sufficient mass to generate a gravitational pull strong enough for this to happen,ergo they wander the universe as misshapen lumps,lump shaped rather than a pleasing rotund ball.
One is postulating yon rock is to small to generate enough gravity to cause it to adopt the spherical configuration it shows and am puzzled. :confused:

27th Jan 2015, 22:47
Depends how 'solid' it was when it formed I suppose.

Mostly Harmless
27th Jan 2015, 22:49
I guess because I made it that way years ago, when I balled-up that rock like a snow ball, and tossed it into the depths of space... Sorry about the inconvenience.

27th Jan 2015, 23:04
Most asteroids are not nearly spherical, for the reason you gave. It's just by chance that this one is.

A survey of main-belt asteroids (see table 5 especially) shows this. There's also a bit on moonlets.

Shape, size and multiplicity of main-belt asteroids I. Keck Adaptive Optics survey (http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2600456/)

Fox 3
Astronomy lecturer in a previous life ;)

tony draper
27th Jan 2015, 23:13
Ah well, tiz after ten and one's head has spun down for the night so shall not even try and read all that, so one shall take your word for it Mr Fox.

Windy Militant
27th Jan 2015, 23:15
Maybe it has a singularity in the middle of it!
More likely it's a Yela spaceship come to envelope the planet in Hydrogen and set fire to us all. ;)

27th Jan 2015, 23:16
one shall take your word for it Mr Fox.

Quite a few have, and they all passed!

Mind you, I did set the exam :E

Maybe it has a singularity in the middle of it!
The Empire has fed all the singularities to the Vogons (apart from the 3 in deep storage in Area 51, obviously)

...or you could goggle "minimum Schwarzchild Radius" if you want another reason why not - e.g. http://physicsforidiots.com/space/black-holes/ ;)

tony draper
27th Jan 2015, 23:20
That's what I fear Mr Militant, that the headlines in tomorrows papers will howl,
Which of course I haven't.

28th Jan 2015, 00:03
Actually one other disturbing aspect of it is its a lot smaller than they thought. What does they do for future trajectory calculations:p.

Also a lesson for other objects that you think we understand but don't. Fortunately most of the objects we see now and are of immediate concern have data that is relevant for at least a few passes in the near future.

28th Jan 2015, 00:17
The Good News - NASA has a Near Earth Asteroid Program which aims to track 90% of potential Extinction Event asteroids by 2020

Near-Earth Object Program (http://neo.jpl.nasa.gov/)

The Bad News - An audit for Congress four months ago reckoned they've only found 10%.

NASA asteroid defense program falls short: audit (http://phys.org/news/2014-09-nasa-asteroid-defense-falls-short.html)

So that's a 90% chance that the first thing we'll know about it is a bloody great bang.

But they only happen every 65 million years or so.

Last major asteroid impact (K-Pg Extinction Event, the Asteroid Formerly Known As K-T Extinction Event) was 65 million years ago....

...next Thursday :ooh: :eek: ;)

28th Jan 2015, 00:22

28th Jan 2015, 01:38
So that's a 90% chance that the first thing we'll know about it is a bloody great bang.

Actually it not that bad. There is a lot more out there looking for them than the US. The good news is the bigger they are the more likely we are to get advanced notice, say 24 Hrs:p

The main issues are the ones that come out from the Sun direction, bit harder to spot.

So probability of big one splatting us is a lot smaller than smaller severe smiting.

28th Jan 2015, 03:26
No one saw the recent Russian meteor coming, about 20 metres in diameter and weighing 10,000 tonnes. Attention at the time was focussed on a 30 metre, 40,000 tonne asteroid (367943 Duende) which passed 16 hours later.


tony draper
28th Jan 2015, 08:35
Seems to me that since we came down from the trees and got the fruck out of Africa in that vast amount of time not a single human being has bothered his or her arse or devoted a single minute of their time worrying about asteroids scragging them or whatever civilization that had managed to cobbled together and indeed not a single asteroid ever did fall on em,yet these last twenty years since we did start worrying about em we are seemingly just dodging the feckers every bloody five minutes.

28th Jan 2015, 10:45
http://i62.tinypic.com/15wcayh.jpg NASA have spotted this small asteroid and have analyised it as pure gold ,they reckon that as it will break up over earth its an Alien plot to destabilize the earths economy so they can step in and take over!!!

28th Jan 2015, 10:58
an Alien plot to destabilize the earths economy so they can step in and take over!!!

They don't need an asteroid to do that, we're making a bloody good job of it on our own.

28th Jan 2015, 11:11
I s'ure did!

28th Jan 2015, 14:31
Alas, I've not been able to give the Admiral's puzzle much consideration: I was distracted by an article about yoga pants farther down the page in his original link:


I can only hope that the next asteroid with which we might have a close encounter will safely pass between the cleft of the Earth and our twin half-moons.

28th Jan 2015, 15:25
a lot smaller than they thought.

So what gave grounds for their "thought" ?

Brightness ? (high or low albedo)

Changes to trajectory caused by nearby masses (so size doesn't correspond to average mass)

Changes caused BY asteroid to other objects in orbit ? (same as above)

Unlikeliness of it having it's own orbiting satellite ? (much more massey than thought)

Needles on massometers all deflecting to the right as it passed the Earth ? (see above)

Appearance on Jerry Springer Show ? (much smaller than thought).

Lets face it, it's small, spherical, very dense....hmmm......

29th Jan 2015, 00:03
Bit like the jumping up in aircraft query, what happens if you are riding along on the space rock, then jump? Get left behind in the void that is space?

Forgot to add....nice buns. All thanks to airship's amazing circle otherwise I would've missed it.

tony draper
29th Jan 2015, 07:50
If you are going to jump on that rock take some sandwidges as it might take you a week to float back down to the ground.:)

tony draper
29th Jan 2015, 08:30
Unless of course yon round rock you land on is not a rock at all but the core of a collapsed star made of pure neutronium,oh dear,your space boots would now weigh in the region of 20,000 tons each and you int jumping anywhere.:uhoh:

29th Jan 2015, 10:42
Thank you gentleman.

Think I'll stay firmly on the ground. Might even take up yoga..:ok:

cockney steve
29th Jan 2015, 11:39
If you was an Asteroid, twirling around and travelling through space for a few million years, I reckon all the space-dust and stuff out there would sandblast off all the sticky-out bits and eventually you'd end up with a ball.....a few million years later, the ball would have been eroded away completely to dust, which would also do it's share of eroding the bumps from any lumps of solid stuff passing through.

I wonder if Earth, following it's orbit, sheds a trail of "stuff" behind it and picks up a coating of stuff left behind on previous orbits?

29th Jan 2015, 12:13
The stuff shedded is mainly hydrogen (95,000 tonnes p.a.) and helium (1,600 tonnes p.a.), volatile gases which escape from the top of the atmosphere. The Earth collects about 40,000 tones of dust p.a.
Uranium radioactive mass loss accounts for 16 tonnes p.a., and global warming energy gain about 160 tonnes p.a.
And recently about 65 tonnes lost per year in satellites, etc, we have chucked off the planet.

Net result: loss of 55,000 tonnes, about 0.000000000000001%, every year

For comparison, the Sun loses 4 million tonnes per second due to nuclear fusion in the core.

Earth data courtesy of Chris Smith and Dave Ansell at Cambridge. Quoted here Saxena & Chandra http://www.ijsrp.org/research-paper-0513/ijsrp-p17109.pdf

29th Jan 2015, 18:37
Now the puzzle, how come the body is so spherical?,surely a 300 meter rock would not generate enough of a gravitational whelt to pull itself itself a spherical shape.?

The most abundant type of asteroid (about 75% of all asteroids) is the C-type. These are composed of carbonaceous chondrites. They contain a large percentage of water (as much as 22%) and many different organic compounds, along with silicates, sulfides, and oxides. They date back to the formation of our solar system and are not broken up "rocks", so a spherical shape is very reasonable.