Asteroid to Make Closest Recorded Pass to Earth

unassimilatible writes "A 100-ft diameter asteroid will make the closest (26,500 miles, or about 3.4 Earth diameters) pass of earth ever detected in advance today, NASA reports. Asteroid 2004 FH's point of closest approach with the Earth will be over the South Atlantic Ocean. Using a good pair of binoculars, the object will be bright enough to be seen during this close approach from areas of Europe, Asia and most of the Southern Hemisphere. While we are in no danger this time, it is good to know NASA's LINEAR guys are on the job, for when that Death Star-sized object pays us a visit."

Bennifer, You're our only hope!?-SarcarticVersion

[mynameis (mother ...]

Guess what everybody: There is another asteroid heading right for us. NEA 2004FH is due to arrive around 5pm EST today. Recently Discovered [nasa.gov], the object is ~30kmmeters [google.com] across, and will pass within 30k miles of earth. "Scientists look forward to the flyby as it will provide them an unprecedented opportunity to study a small NEA asteroid up close." Also worthwhile, the view showing it's orbit [superimposed over our's] notes "The locations of the asteroid and Earth are indistinguishable at this scale."

• Which should be shattering to all those who felt their Solar-model-with-lightbulb-as-sun was truely 'to scale.'
• 
  Affleck was not immediately available for comment.

[caugh]How can this not be the 11th planet: it has a rather round orbit that is very similar to earths own?! [/caugh]

In related news, Ron Page now claims this was the 'NEA' he was referring to as terrorist last month. [cnn.com]

This is sserious

[cda]

Section of an IAU Statement prepared by Dr. David Morrison, 14 March 1998
The International Astronomical Union's (http://www.intastun.org/) list of 108 known ''potentially hazardous objects,'' or PHOs.
Most of the asteroids that could strike the Earth and cause a global catastrophe have not yet been found. For the year 2028 (or any other year) the chances of an unknown asteroid hitting the Earth are much greater than the chances of this particular asteroid hitting. If an unknown asteroid should hit us, we would likely have no warning at all. The first we would know of the danger is when we saw the flash of light and felt the ground shake. At the current rate of discovery, it will take more than a century to find 90% or more of the objects this large with Earth-crossing orbits. For better or for worse, the astronomers who carry out these searches and orbit calculations work in the public eye. The idea that a threatening asteroid could be kept secret (or that anyone would want to keep it secret) is ludicrous.
For further information see the NASA asteroid and comet impact hazard website at:

Impact risks

[xlation]

For a long list of Potentially Hazardous Asteroids (PHAs) see: http://cfa-www.harvard.edu/iau/lists/PHACloseApp.h tml

Also, for information on assessment of the
impact risks using the Torino Scale, which is
kinda like the Richter Scale for impact risk,
see: http://neo.jpl.nasa.gov/risk/

How far away?

[pesc]

A 100-ft diameter asteroid will make the closest (26,500 miles, or about 3.4 Earth diameters)

If "feet" or "earth diameters" are not your preferred units of measurement, what the article is trying to say is that the asteroid is about 90m in diameter and will pass the earth at a distance of about 42600 km.

Re:Gravitational Effects?

[kalidasa]

It's 30 m across, and the earth is 12,760,000 m across, volume is pi r^2, assuming the same density, and gravity is proportional to mass - probably not. If we could do that, we wouldn't need line of sight radar - we could just track airplanes by their gravitational effects without line of sight.

Re:How far away?

[pesc]

Ouch! meant 30m in diameter. *blush*

Re:Lucky

[0x41]

Skylab was going 100 times slower than this asteroid, hence it didn't burn up.

Re:Gravitational Effects?

[cperciva]

100' diameter ==> 15m radius ==> around 15000 m^3 ==> somewhere around 5x10^7 kg if it's rock.

26500 miles is around 4000 times further away from the surface of the earth than the 35,000 feet at which planes fly.

So the gravitational effect this rock will have at the surface of the earth is around the same as the effect from a 3kg bag inside a plane flying overhead. Probably not noticable. :)

Re:Gravitational Effects?

[Anonymous Coward]

This force of gravitational attraction is directly dependent upon the masses of both objects and inversely proportional to the square of the distance which separates their centers.

Re:Lucky

[tiled_rainbows]

But Skylab wasn't going as fast - Celestial mechanics isn't my strong point, but something falling from a gradully-decaying orbit around the Eath (eg Skylab) won't be going half as fast relative to the Earth as something aproaching perihelion on a huge elliptic orbit round the sun (eg an asteroid) - things on elliptic orbits go faster the closer they get to the thing they're orbiting. Conservation of angular momentum or something.

And as Skylab wasn't going as fast, it wasn't heated up so much in the atmosphere, so more bits of it reached the surface than most meteorites.

Re:um and?

[tilmanb]

>>Ok so in the future we will know when a 100km diameter asteroid is gonna hit earth.

>You realize that a 100km asteroid would not be an asteroid, it would be the second largest planet in our solar system (jupiter being around 140km)

There is a slight mistake here (mod parent wrong!):

Jupiter has not 140km diameter but 140k km (142984 km to be exact).

Re:Gravitational Effects?

[ThosLives]

Well, it's not that hard to figure out. Assume the 100' diameter (30.48m) thing is a sphere made of solid steel (density ~8000 kg/m3). That sphere has a volume of 14,827 m3, so would have a mass of ~118.6e6 kg. At a distance of 26,500 miles from earth's center, it will exert a force of 2.6e7 newtons (about 3000 tons) on the earth. This would make the earth accelerate toward the asteroid at only 4.3e-18 m/s2 (the asteroid, though, accelerates toward earth at a whopping 0.2 m/s2).

If you were standing on the asteroid, and you weigh 150 lbs on earth, you'd weigh only 0.0005 lbs (assuming the asteroid was the only thing around).

If you were standing on earth and the asteroid were directly over your head (at 26,500 miles from your center) and you weighed 150 lbs, it would reduce your weight by 6.6e-17 pounds. Not exactly a weight-loss program.

Those numbers seem pretty hard to detect directly, but we might be able to use indirect means.

Re:Lucky

[GooberToo]

Mod the parent back down. The AC which already replied and was marked as flambait is right. This guy is an idiot. The only exception where his statement might hold water would be if the object were solid water...and then, maybe. And then, it wouldn't be because of "pressure differences", it would be because of super heating, causing steam to form inside, causing it to explode.

Re:Lucky

[K1-V116]

The meteor that made Barringer Crater in Arizona (1.6k across and nearly 200m deep) was ~45m in diameter -- only about 50% wider and roughly twice the mass of the one detected. This rock _could_ have spoiled someone's day....

100 ft may seem small, but ....

[innerweb]

From what I am reading in the articles on the net, 100 feet can still create some serious, albeit localized damage. If this bad boy were to hit over the ocean, probably not much, but over land, it could cause serious local destruction. Anyone out there serious about their astronomy?

The Tunguska Blast [sciam.com] over Siberia was an object about 100 meters in diameter. Sure it burned up in the atmosphere, but it was devastating to the ground anyway. This article also mentions that at about 50 meters, these rocks make it through the atmosphere and can do serious localized damage. So, since 100 feet converts [teaching-e...-japan.net] to is 30.48 meters, this rock would more than likely to have an effect that we will notice on the ground.

For further reading, here is a site [pibburns.com] that has already compiled links and information And, of course, the Yahoo listings [yahoo.com] on Earth Impact information online.

InnerWeb

Meteor Crater

[Anonymous Coward]

An 80ft asteroid caused Meteor Crater at 1.2km wide. A 100ft one may likewise not burn up. Meteor Crater [nasa.gov]

Solar system collisions simulator

[copper]

Plug in some numbers and find out [umd.edu] :)

copper

Distributed seeing

[jmichaelg]

The computations aren't that hard given the quality of data they have to work with. A lot of these objects are spotted once and never seen again for a variety of reasons. What's needed are more data, not more cpu cycles.

Amatuer astronomers continue to make significant contributions to the field. It was an amatuer who first noticed that al0667 might hit the earth and it was another amatuer who recorded the key observation that placed the same object on a safe trajectory. If you're serious about wanting to help spot these things, you can start here. [harvard.edu]

Re:Lucky

[DigitumDei]

Not quite pressure differences inside.
Taken from the following NASA article. [nasa.gov]

Asteroids move faster than the speed of sound in Earth's atmosphere. As a result, the air pressure ahead of a fireball can substantially exceed the air pressure behind it. The difference can be so great that it actually crushes the object

Re:Meteor Crater

[SeaDour]

Correction, it was an 80 ft. *METEOR* that created that Arizona scar. The asteroid was probably much, much larger before it plunged through the atmosphere and shrunk into that 80 ft. meteor. - Asteroid: the rock before it touches our atmosphere - Meteorite: the rock as it's plunging through our atmosphere - Meteor: the rock after it's hit the ground.

Perhaps you should actually read what it says

[hpulley]

...While we are in no danger this time, it is good to know NASA's LINEAR guys are on the job, for when that Death Star-sized object pays us a visit.

The heading doesn't say the current 100 ft object is Death Star-sized. It says the author is glad LINEAR will be on the job for the time when one that large comes by.

Re:Lucky

[HeghmoH]

The speed doesn't make as much of a difference as you'd think. You're going faster, but you also have much less time for the heating to have any effect. The direction of travel is also important. If the asteroid were traveling perpendicular to the atmosphere, the parts of the atmosphere that matter are only about 50 miles thick. Typical combined speeds for an object coming from solar orbit are in the range of 20-30 miles per second. In that case, the asteroid would only have about two seconds to completely vaporize before it met the ground. Even if it did vaporize, you still get all of the energy it contains being released in a giant explosion. Assuming this rock is made of solid iron (which is most likely not correct, but it should be roughly correct for the density), I get a figure of about 100 thousand tons for its mass. By contrast, Skylab was 76,295kg; less than a thousandth of the mass.

Re:Lucky

[avgjoe62]

Very true, but remember that the atmosphere will slow the object, and that such objects rarely approach the Earth straight on. More often, they strike at an oblique angle. The Peekskill meteor crossed the sky for forty seconds.

More worrisome to me is "Neun und Neunzig Luftballon" scenario, where an incoming object explodes in the atmosphere, is mis-interpreted by NORAD and Whoops! It's Armageddon!

Some Deductions

[LaCosaNostradamus]

Look at the facts and deduce your answer. I didn't have time to googleconfirm any of this, so I assume the risks of some numerical errors.

Man-made objects that come down are very light, hollow and fairly slow. Asteroids and comets are guaranteed to be the opposite.

Asteroids are 2 different types: metallic, stony and finally "carbonaceous chondrite". The metallic are essentially chunks of nickel-iron. The stony are just rock. And the CC types are rocky but composed significantly of some ices and other nearly-organic material.

(Comets are mostly icy material with some rocky inclusions ... there may even be a small core, or it may end up being a rubble pile after most of the ices burn away. The 1908 Tunguska event was probably a small comet, which exploded in the strato- or tropo-sphere. Still, it caused enormous damage in a vast ellipse over Siberia.)

Knowing these things, we can perhaps make some deductions.

A 100ft object of asteroidal material (often compacted rubble) probably weighs at most 120LB per cubic foot. I say this since 150LB/ft3 is a good rule of thumb for any rock you pick up on Earth. Hence, assuming a roughly spherical shape, the object will weigh ~31000 tons.

The largest man-made object to destructively re-enter couldn't have exceeded 100 tons. Hence, the object is over 300 times more massive.

It is also coming in at interplanetary speeds; since these tend to be about 30km/s, and orbit is about 7km/s, then it will encounter (30/7)^2 more resistance upon re-entry ... about 16 times the forces ever encountered by Mir or Skylab.

Opposing that: 300 times the mass. I can only imagine that the mass will win.

Now, "win" means that it will overpower destructive re-entry ... that it probably won't "burn up". But we must allow for the chances of mid-entry detonation.

This depends on what type of asteriodal material that the 30m object is, and how that material is arranged. The less metallic, and the more rubblized, then the greater the chances that it will explode, and the higher up it will do so. Even at 31kt mass, re-entry is harsh enough to force streams of plasma into even small cracks, and the pressure can crack it open along many fault lines. With volatile ices stuffed through the object, this becomes even more explosive.

Overall, even not knowing the object's composition except to bet that it's asteroidal and not cometary, I'd say that if it did aim for the Earth, we'd be in for at least a huge explosion in the upper atmosphere. I don't have the equations sitting before me, but such an explosion can be in the ten-megaton range. But this explosion can happen anytime before it strikes the ground.

Re:I'd hate to be a

[MURL]

Geosynchrous orbit is 22,500 miles or 36,210 km. This thing could definitely take one out.

Almost geosynchronous height!

[pvera]

Back in my Army SSDC days our main geosynchronous comms satellites were on a 22,300 mile orbit. This thing is going to pass just above. Suddenly these 26,500 miles don't look *that* far to me.

Are we on the bullseye in 2053?

[Liquor]

I may be reading the impact risk table [nasa.gov] wrong, but right now it seems to say that the distance it will miss by on Jan 12, 2053 is .01 earth radius. I assume that this means that we are very near the center of the area of uncertainty about where it will impact, and that the areo of uncertainty is currently extremely large.

On the other hand, I seem to recall that most previous predicted near misses had us further out from the centroid, and as the orbital data was refined, the area of uncertainty shrank until we were no longer in it. I suspect that reducing the uncertainty without changing the orbital prediction would raise the calculated risk with time.

As I read it the impact energy would be about equal to a 300Kiloton bomb. Not a particularly large hazard area if it came straight down (it probably won't), but it would certainly be big enough to mess up somebody's day. For that matter, has anyone actually run a prediction of what the effects (thermal, weather, etc.) would be from a grazing strike where it travelled parallel to the surface for a long way before breaking up or leaving the atmosphere?

Re:Lucky

[AJWM]

It'd be like nuclear detonations, only without the radiation.

Oh, from an explosion like that, you'll get radiation -- X rays and such from the high temperature plasma. Just not us much radiation (no neutrons) as from a nuke, and no fallout. (Well, not radioactive fallout. Plenty of dust.)

Re:Lucky

[AJWM]

50% wider and roughly twice the mass of the one detected

If both bodies were the same shape the larger would have eight times the volume.

Er, 1.5^3 = 3.375, not eight. Other than that you're doing fine ;-)