Slashdot Mirror
Unknown 7m Asteroid Almost Impacted Earth
xp65 writes "A previously undiscovered asteroid came within 14,000 km of Earth — just over one Earth diameter, 1/30 the lunar distance — on Friday, and astronomers noticed it only 15 hours before closest approach. On Nov. 6 at around 16:30 EST, a 7-meter asteroid, now called 2009 VA, came only about 2 Earth radii from
impacting our planet. This is the third-closest known non-impacting Earth approach on record for a cataloged asteroid. The asteroid was discovered by the Catalina Sky Survey and was quickly identified by the Minor Planet Center in Cambridge MA as an object that would soon pass very close to the Earth. JPL's Near-Earth Object Program Office also computed an orbit solution for this object, and determined that it was not headed for an
impact." The article notes, "On average, objects the size of 2009 VA pass this close about twice per year and impact Earth about once every 5 years."
Anybody want to weigh in?
You expect nerds and geeks to give their actual weight online?!
The article doesn't say what level of damage would have resulted from an impact. Anybody want to weigh in?
I remember my old science book said that the one responsible for Meteor Crater was the size of a box car but that's kind of imprecise. It's a question of mass and velocity. The looser, rock-ice bodies tend to explode in the air. We've had a couple historically that were big enough to be mistaken for nuclear tests but they exploded high in the air over remote stretches of ocean.
Kwisatz Haderach
Sell the spice to CHOAM
This Mahdi took Shaddam's Throne
a flying rock! call a geoligist!!!
Since it claims objects that size impact Earth about once every 5 years, the damage would be the same that we see every time one of these impacts. If you can't think of the last time that happened or you can't think of a damage report about that, then that should be your answer.
"Our two-party system is like a bowl of shit looking at itself in a mirror." - Lewis Black
Seven meters just isn't all that big. According to the Earth Impact Effects Program using typical data: No crater is formed, although large fragments may strike the surface. The air blast at this location would not be noticed.
From Wikipedia:
If it hit near the center of a large city it could really suck; however, most of the earth's surface is covered by water, desert, mountains, or rural areas, and thus most asteroid impacts of this size do not cause massive loss of life.
Nonaggression works!
It would most likely bursts into a cloud of fragments at an altitude of 8980 meters. Minor local damage might occur if a larger fragment happens to hit a house.
http://www.lpl.arizona.edu/impacteffects/cgi-bin/crater.cgi?dist=0.001&diam=7&pdens=&pdens_select=8000&vel=17&theta=45&tdens=2500&tdens_select=0
Comment removed based on user account deletion
This seems like a nonsensical conclusion -- larger objects are easier to detect, both by virtue of being larger and, since they are a potential threat, are more worthy of attention and effort.
TFA says 7 meters - which is still 30% smaller than what you quote. 30% off a hiroshima bomb is a lot. Not to mention that the composition of the object has quite an effect as well. I'm going to let a source that carries a little more weight to, well, weigh in on it.
What? I can't assume Occam's Razor was a slick fold-up scooter?
Comment removed based on user account deletion
Are you kidding? That thing can't even stand up to a bird with a bagel.
25% Funny, 25% Insightful, 25% Informative, 25% Troll
You can use this site to get an estimate.
And I forgot to consider that this was an object of 10 meters or so when it impacted Earth and was thus likely far bigger before entering the atmosphere. An object that was 10 meters before entering the atmosphere would, depending on composition and angle of descent, likely burn away completely before reaching ground. But there might be a midair explosion or fireball sufficient to ignite highly flammable structures.
Nonaggression works!
The energy would correspond to the mass rather than the radius; assuming constant density we can use volume so 7^3/10^3=0.343 or 34% of the energy of the 10m asteroid. I don't know my meteor impact science, but I wouldn't be surprised if the higher surface/volume ratio means proportionally more of it burns up in the atmosphere to reduce the impact energy even further.
Regardless, a post farther down links to an impact calculator that claims it bursts in mid-air and results in no significant impact, so this speculation is moot (I am assuming the calculator is well-written).
My webcomic
I'm sure if it had been on course to hit Earth, it would have burned up in the atmosphere and whatever's left would be no bigger than a chihuahua's head.
Dewey, you fool! Your decimal system has played right into my hands!
Join the Mobile Infantry and save the Galaxy. Service guarantees citizenship. Would you like to know more?
"Be prepared, son. That's my motto. Be prepared." --Joe Hallenbeck
AKA Not Much
Unless it lands on your house!
Error reading device 'Signature'. (A)bort, (R)etry, (F)ail?
We track 90% of the near-earth objects that have a possibility of causing global catastrophe. While there's certainly room for improvement, we've actually been doing quite a lot of looking.
To give a sense of scale, global-catastrophic asteroids are 1 km in diameter; this one was 7 m.
Would it penetrate through to basement depth? If not most people here wouldn't notice till the next meal didn't show up.
Confucius say, "Find worm in apple - bad. Find half a worm - worse."
Verbogeny is one of many pleasurettes afforded a creatific thinkerizer.
Depends. Is there a modifier for a sneak attack?
yeah, +3 HOLY SHIT A FUCKING METEOR!
"I disapprove of what you say, but I will defend to the death your right to say it." - Evelyn Beatrice Hall, re Voltaire
As a nitpick, that's actually 40 kiloton equivalent (0.40 x 10^-1 megatons = 0.04 megatons = 40 kilotons). You don't get a 400 kiloton airburst until you go up to 15m diameter
10 PRINT CHR$(205.5+RND(1)); : GOTO 10
I think the official name is a "Basement Level Event"
// MD_Update(&m,buf,j);
Womprat = 2m
Asteroid = 7m
If by not much bigger you mean nearly triple the size... then yes. It's not much bigger.
this has been you Star Wars nitpick of the day. Thank you.
40 Kiloton, 40. Not 400.
Say you're a new galactic overlord driving a car, but you're in space, and you're drunk. You see this big blue planet getting bigger and bigger in your windscreen. At the last possible moment, you hear me yelling to get the hell off my lawn, you suddenly swerve, and miss. But you've ruined Cowboy Neal's tulips, you insensitive clod!
"This post contains words, known to the State of California to cause thought. Wash brain thoroughly after reading."
It would most likely bursts into a cloud of fragments at an altitude of 8980 meters. Minor local damage might occur if a larger fragment happens to hit a house.
http://www.lpl.arizona.edu/impacteffects/cgi-bin/crater.cgi?dist=0.001&diam=7&pdens=&pdens_select=8000&vel=17&theta=45&tdens=2500&tdens_select=0
Thanks for not rounding that off to "nine kilometers" or even "about 10 km" as some less mathematically-inclined contributors would have done. If you've laboriously and precisely calculated that 2009 AV is exactly 7.000 meters in diameter, has a density of 8.000 g/cm3 and will hit the atmosphere at a 45.00 degree angle at exactly 17.00 km/s, why give up that hard-earned precision in your result?
Keeping in mind, of course, that most of the Earth is unpopulated -- in all likelihood the asteroid will strike an ocean (unless a very unlucky ship is hit, nobody would notice this) or a desert/forest (again, someone would have to be very unlucky for this to be noticed). Some of the land impacts may never be discovered -- by the time anyone passes near the impact site, natural forces would probably have erased the crater.
Palm trees and 8
Hmmm... well, I realize that checking a dictionary first would've been a lot of work, but here's what m-w has to say about it. Note that the first entry is for the verb "impact".
I shoved some numbers in, making it quite dense with the recommended average velocity for an asteroid, impact angle etc and got the following results:
Your Inputs:
Distance from Impact: 1.00 km = 0.62 miles
Projectile Diameter: 7.00 m = 22.96 ft = 0.00 miles
Projectile Density: 3000 kg/m3
Impact Velocity: 17.00 km/s = 10.56 miles/s
Impact Angle: 45 degrees
Target Density: 2500 kg/m3
Target Type: Sedimentary Rock
Energy:
Energy before atmospheric entry: 7.79 x 1013 Joules = 0.19 x 10^-1 MegaTons TNT
The average interval between impacts of this size somewhere on Earth is 5.1 years
Atmospheric Entry:
The projectile begins to breakup at an altitude of 54000 meters = 177000 ft
The projectile bursts into a cloud of fragments at an altitude of 34300 meters = 113000 ft
The residual velocity of the projectile fragments after the burst is 13.7 km/s = 8.49 miles/s
The energy of the airburst is 2.75 x 1013 Joules = 0.66 x 10^-2 MegaTons.
No crater is formed, although large fragments may strike the surface.
Major Global Changes:
The Earth is not strongly disturbed by the impact and loses negligible mass.
The impact does not make a noticeable change in the Earth's rotation period or the tilt of its axis.
The impact does not shift the Earth's orbit noticeably.
This does not indicate a question of looking in the right direction. Seeing something that small is basically impossible until its right on top of us even if you're looking straight at it, which is fortunate since its not a big concern. Compare a 7 meter asteroid with a 300 meter asteroid such as 99942 Apophis:
Since surface projection is proportional to the radius squared, Apophis is likely to be 100,000 times brighter, or around 12.5 stellar magnitudes. During the 2029 close approach, when Apophis will be within the geostationary belt, it will be magnitude 3.3, meaning that a 7-meter asteroid would be around magnitude 16. This is below the limiting magnitude of most telescopes being used in these searches, so only the very large (1+ meter) would be able to find it even when that close.
Also, there are a number of individuals doing this in addition to the official NASA work. This was processed through the Minor Planet Center in Cambridge, to which it is quite easy to submit information on new asteroids. With automated amateur equipment (the well-funded 60 year old amateur, not the $200 14 year old amateur) its quite easy to set up a system to automatically observe a region of sky and detect asteroids. If you have a series of plates indicating an asteroid, they can be submitted to the MPC through automated software and its all logged. You may not be satisfied, but its certainly not nothing, even if the NASA effort itself is underfunded.
What about tsunamis?
Well, other posters have established (well, speculated) that the impact energy would be significantly less than the Hiroshima bomb... there's a link elsewhere in this thread which discusses that a meteorite with a diameter of 10m on impact (meaning significantly larger than 10m when it entered the atmosphere) would have about the explosive force of the Hiroshima bomb.... The number that people are throwing around seems to be around 30-35% of the impact energy, if it hit the ground with a diameter of 7m. I'm going to have to rely on other peoples' calculations, but it does seem to be supported by others.
Let's assume 33%, because the math's easy. The Hiroshima bomb exploded with a peak force of about 18kt, according to Wikipedia. 1/3 of that is 6kt. This is an important number... by any account, it's a big explosion. The largest conventional explosive currently in use in the world is the US-built Massive Ordnance Penetrator (MOP) with a blast yield of 13.6 tonnes... we're talking 400 times more explosive force. If it hit a city with that kind of force, it would do extensive damage.
But let's put this in perspective, and actually answer your question: On May 5, 1954, the US Navy set off Castle Yankee, part of the Operation Castle set of nuclear weapons tests, on the surface of the ocean off Bikini Atoll in Micronesia. The yield of this bomb was 13.5mt, more than 2000x more powerful than this meteorite could possibly be, even assuming that it did not shed any mass at all during entry. Castle Yankee did not cause a tsunami. The likelihood of such a meteorite causing a tsunami is slim to nil.
The real question is would it impact at all.
How much would burn up after breaking up in the atmosphere.
If one of these impacts every 5 years, and 65% of the earth's surface is water, you would expect 1 of every 3 or 4 to land on dry land, so in 20 years we should have had some impacts in places they can be found.
Since no one here can remember the last one, you have to assume the damage has been minimal.
Sig Battery depleted. Reverting to safe mode.
What's your point???
Because we don't actually know we're tracking 90% of NEOs. We estimate that we're tracking 90% of them. We can't actually know we're tracking them, because we simply haven't discovered them all. (comparatively) tiny objects in a slow orbit that may cross our own orbit at some point in the future, but that are so dark that they're black, and so cold they're hard to tell from the ambient radiation on the infrared and other bands? The unfortunate reality is that we just can't see some of what's out there, either because we haven't looked in the right part of space with the right equipment, or because the right equipment doesn't exist.
We figure we're probably tracking about 90%, based on our estimates of the mass of the solar system and how much of what we're actually tracking. We could be tracking 100% of the stuff that actually poses a threat. We could be tracking 50% of it. But the best guess we actually have is that we're somewhere around 90% at the moment, and that the number will go up over time. But we still might never see the one that wipes us out.
Perhaps a better question is: if we can detect the one that's about to hit us, are we likely to be able to do anything about it?
According to this (I didn't verify any facts) - http://wiki.answers.com/Q/How_much_of_the_Earths_surface_is_inhabited_by_humans
About 1% of the surface is inhabited. So, an impact should directly affect people about once every 500 years. Maybe it's the next time?
None. We were hit by one about 10 meters across on October 8th but no one wants to put the story out for some reason. http://neo.jpl.nasa.gov/news/news165.html
It all starts at 0
(If the link breaks, the book is Merriam-Webster's dictionary of English usage)
The link is not broken, and here are two snippets that jumped right out at me:
"But since part of the criticism seems to be based on the erroneous notion that that the verb is derived from the noun based on functional shift, we must first pursue a little "
and
"But impact was a verb in English before it was a noun."
and
"This is not a case of a verb derived from an earlier noun."
In summary:
While impact as a verb has been around for a long time, it was not until the '80's that it began to be used in business and political contexts as a buzzword substitute for 'affect'.
To the extent that the link supports that view (m-w says you can avoid impact(v) if you like, but does not suggest it's in any way incorrect, and has numerous examples from the 70s), it's talking about the figurative uses of the verb. Whereas the usage in question here is the literal use of the verb, and is 100% irrefutably correct usage since 1601.
So if that usage "sounds wrong", I think the advice of Meriam-Webster's Dictionary of English Usage is to get over yourself and your incorrect notions.
The enemies of Democracy are
You don't get a saving throw against an attack roll in the standard rules for 3.0 or 3.5. I don't think you get one in 4.0 either but I refuse to check unless I absolutely need to. Now, if Earth had class levels in rogue that were high enough and the asteroid had few or no class levels in rogue then Earth wouldn't get the sneak attack damage. I don't know how you check what class levels an asteroid has. Considering that they can't get XP (since the only way they end up at the end of an encounter is dead) they can probably only get class levels if they started that way or if God is a generous DM who gives a lot of XP for roleplaying. However, I'm not sure that asteroids are very good at roleplaying. They don't talk much and when they do you generally don't hear it because of the vacuum.
1.3E-5 Library of Congresses
I swear to God...I swear to God! That is NOT how you treat your human!
Asteroid Impact Calculator. Handy thing to have bookmarked, in the event that the astronomers see the next one from far enough off.
It's impossible to be sure what the density and angle of incidence would have been in this case, as this sort of data isn't usually published. It's also impossible to be sure of composition, as that depends on where the asteroid was from. Thus, any results you DO get from the calculator are either meaningless (too much garbage in) or extreme values only.
Having said that, such calculators are fun when they find truly massive craters. The crater under the antarctic ice, for example, is so large that the Earth was unlikely to have ever been hit by something that big in the past 4 billion years. Antarctica is very modern, in comparison.
It's a small world and it smells funny; I'd buy another if it wasn't for the money; Take back what I paid (SoM)
Apophis is likely to be 100,000 times brighter
(300 / 7)^2 = about 1,800, which is not very close to 100,000
You're right. I accidentally typed in (300*300/7*7) instead of (.../(7*7)). Mea culpa.
At any rate, its around 10 stellar magnitude off, which means it would be around magnitude 14 on a very near approach. This is just barely visibile in a 16" telescope, so its still very hard to see.
Handy thing to have bookmarked
Sounds like a good thing to ping every so often. If the latency goes up or it stops responding altogether then the chances are that a whole load of people somewhere know something that you don't.
As a comparison for the non-astronomers:
In college, we had a pretty sweet 0.8m diameter scope. The limiting resolution of that was about 12 magnitude. Magnitude goes up as powers of ten. So 16th magnitude would be 10^4 times dimmer than what we could see with that scope. Even a 1m scope would have issues with that. You'd need fantastic conditions and very, very good mechanics to be able to take exposures long enough to reliably capture 16 magnitude.
Take into account that we can only reliably detect asteroids based on lateral movement against the constant stars in the background, and you have situations like this where the asteroid is nearly undetectable. Keep in mind that the only light is from the sun, and the asteroid is likely as reflective as pavement. Then that reflected light radiates out spherically, and the intensity fades out as one over the square of the distance between the asteroid and the telescope.
There are plenty of asteroids we'll never be able to reliably detect and track. As long as we do so with the ones over 20m, we should be ok. We'll definitely see most of those in time to wring our hands and turn to prayer, for lack of any better way to deal with them.
Velociraptor = Distiraptor / Timeraptor
£170. Sorry, I don't have it in USD
"We returned the General to El Salvador, or maybe Guatemala, it's difficult to tell from 10,000 feet"
They really needed it 250-300 million years ago though. Tweaking the impact velocity to get roughly the right values according to the article, the calculator reveals anyone on the edge of the crater would be vaporized, ripped to shreds from the pressure wave, then pulverized by the earthquake and drowned by a subsequent tsunami.
Now, THAT is what I call having a bad day.
It's a small world and it smells funny; I'd buy another if it wasn't for the money; Take back what I paid (SoM)
Perhaps a better question is: if we can detect the one that's about to hit us, are we likely to be able to do anything about it?
no
I am very sucseptible to "let's have another drink"