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Comments: 289 +-   Unknown 7m Asteroid Almost Impacted Earth on Tuesday November 10, @02:21PM

Posted by kdawson on Tuesday November 10, @02:21PM
from the just-passing-by dept.
space
science
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."
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  • Way to sensationalize an asteroid that isn't much bigger then a womprat. If it had hit the Earth, very few people (if any) would have even noticed.
    • Re:OH NOES!!! (Score:4, Interesting)

      by Absolut187 (816431) on Tuesday November 10, @02:33PM (#30050102) Homepage

      I think the *point* is that we didn't know about it until 15 hours before its closest approach.

      The obvious implication being that there could easily be many more out there, possibly much bigger, and possibly on a collision course with earth.

      We just dodged a bullet, and you're basically saying "so what, it would only have been a flesh wound anyway".

      We had this same discussion [slashdot.org] a few months ago, and it seems like most people on Slashdot think this is no big deal. I hope they are right, because we sure don't seem to be doing much about it.

      • Re: (Score:3, Insightful)

        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.

        • Re:OH NOES!!! (Score:4, Informative)

          by Absolut187 (816431) on Tuesday November 10, @02:42PM (#30050242) Homepage

          They're only easier to detect if you're looking in the right direction.

          If you've only surveyed a small fraction of the relevant space, you've likely missed all objects of ALL sizes.

          According to NASA they are tracking 90% of 1km NEOs, but they aren't satisfied with that and neither am I.

          http://arstechnica.com/science/news/2009/08/nasa-asteroid-tracking-program-stalled-due-to-lack-of-funds.ars [arstechnica.com]

          • Re:OH NOES!!! (Score:5, Insightful)

            by Nyeerrmm (940927) on Tuesday November 10, @03:34PM (#30050938)

            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.

            • Re: (Score:3, Informative)

              Apophis is likely to be 100,000 times brighter
              (300 / 7)^2 = about 1,800, which is not very close to 100,000

              • Re: (Score:3, Insightful)

                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.

            • Re: (Score:3, Informative)

              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

          • Re: (Score:3, Informative)

            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.

              • Re:OH NOES!!! (Score:5, Insightful)

                by realityimpaired (1668397) on Tuesday November 10, @03:56PM (#30051256)

                If we know we're tracking 90% of NEOs, why not the other 10%?

                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?

    • by mrdoogee (1179081) on Tuesday November 10, @03:06PM (#30050584)

      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.

  • wah! (Score:5, Funny)

    by thhamm (764787) on Tuesday November 10, @02:27PM (#30049990)
  • by Conchobair (1648793) on Tuesday November 10, @02:29PM (#30050040)
    Seven meters just isn't all that big. According to the Earth Impact Effects Program [arizona.edu] using typical data: No crater is formed, although large fragments may strike the surface. The air blast at this location would not be noticed.
  • Join the Mobile Infantry and save the Galaxy. Service guarantees citizenship. Would you like to know more?
    • by CannonballHead (842625) on Tuesday November 10, @02:26PM (#30049954)

      Anybody want to weigh in?

      You expect nerds and geeks to give their actual weight online?!

    • Re: (Score:3, Interesting)

      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.

      • Re:How Much Damage? (Score:5, Informative)

        by jd (1658) <imipakNO@SPAMyahoo.com> on Tuesday November 10, @05:32PM (#30052698) Homepage Journal

        Asteroid Impact Calculator [arizona.edu]. 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.

    • by amicusNYCL (1538833) on Tuesday November 10, @02:29PM (#30050034)

      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.

    • Re:How Much Damage? (Score:4, Interesting)

      by Joey Vegetables (686525) on Tuesday November 10, @02:30PM (#30050056) Journal

      From Wikipedia [wikipedia.org]:

      An impact by an object in this size range [around 10m] would correspond to an impact energy roughly comparable to the Hiroshima bomb, if the object had hit the Earth's surface.

      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.

      • Re: (Score:3, Interesting)

        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.
        • Re:How Much Damage? (Score:5, Informative)

          by Joey Vegetables (686525) on Tuesday November 10, @02:46PM (#30050278) Journal
          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.
        • by T Murphy (1054674) on Tuesday November 10, @02:48PM (#30050312) Journal
          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).
        • Re:How Much Damage? (Score:4, Informative)

          by realityimpaired (1668397) on Tuesday November 10, @03:41PM (#30051028)

          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.

    • Re:How Much Damage? (Score:5, Informative)

      by dvice_null (981029) on Tuesday November 10, @02:32PM (#30050086)

      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 [arizona.edu]

    • Re:How Much Damage? (Score:5, Informative)

      by olsmeister (1488789) on Tuesday November 10, @02:44PM (#30050264)
      You can use this [arizona.edu] site to get an estimate.
      • 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 interva

    • 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.
    • by zerosomething (1353609) on Tuesday November 10, @04:34PM (#30051846) Homepage
      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 [nasa.gov]
      • by spidercoz (947220) on Tuesday November 10, @03:05PM (#30050572) Journal

        Depends. Is there a modifier for a sneak attack?

        yeah, +3 HOLY SHIT A FUCKING METEOR!

        • 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) th
    • 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!

    • Re:"Impact" Earth? (Score:5, Informative)

      by mea37 (1201159) on Tuesday November 10, @03:20PM (#30050760)

      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 [merriam-webster.com]. Note that the first entry is for the verb "impact".

            • (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

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