The last reports (from the Russian Academy of Sciences) suggest that it disintegrated (with the power of a small nuke, so 'explode' would be an alternative description) 30-50km up in the atmosphere.
The last reports (from the Russian Academy of Sciences) suggest that it disintegrated (with the power of a small nuke, so 'explode' would be an alternative description) 30-50km up in the atmosphere.
Thank goodness it wasn't misinterpreted as something other than a meteor .....
For the record the Russian meteor is not related to the asteroid near miss, just a coincidence. Parts of it are in a frozen lake and presumably will be recovered and
analyzed in due course. I've also heard 10 tonnes (which isn't anything like 17m diameter), but that might mean a fragment on the ground, not the original size.
For the record the Russian meteor is not related to the asteroid near miss, just a coincidence. Parts of it are in a frozen lake and presumably will be recovered and
analyzed in due course. I've also heard 10 tonnes (which isn't anything like 17m diameter), but that might mean a fragment on the ground, not the original size.
The suggested weight has been estimated loosely at 500 tons.
The problem isn't that we aren't "tracking" such small asteroids, it's that we can't see them at all except when they're extremely close to earth. The detection limit is only roughly set by the size of the asteroid. The position relative to the earth and sun and instrument sensitivity are the biggest factors; even large asteroids are faint when far away. WRT tracking, only when there are relatively close encounters between an asteroid and a larger body does the orbit change appreciably, in most cases once the orbit is known the asteroid can always be found so there's no need to track it per se. For that reason asteroids also don't really leave the asteroid belt except in the rarest circumstances. The asteroids and planets have been doing their little orbital dance for eons and so the asteroid belt as it exists is what's left after all the unstable orbits have been swept clear. Nearly all the opportunities for a planet like Jupiter to perturb asteroid orbits significantly have already happened many times. That said, there are still a lot of asteroids around whose orbits were disrupted some time in the past such that they became earth-crossers or one of the other families already mentioned. Most asteroids in oddball orbits are vicitms of some past gravitational encounter with Jupiter. They just haven't hit anything. Yet.
The instruments used for detecting asteroids can only see so faint. The detectors are pretty good already, with very high quantum efficiency so there aren't a lot of photons going to waste. To go fainter, you need bigger telescopes. But bigger scopes tend to have longer focal lengths, which means the field of view gets smaller so you cover less sky in any one image. That means you need more of them to get adequate coverage. In the grand scheme of things, the rock that hit Russia was very unusual. It was very large (compared to most that hit the earth), it hit land when 3/4 of the planet is water, and it hit a fairly densely populated area when most of the land is wilderness. Even then, the damage was relatively minor, and I think given the odds of it happening that you'll have a hard time convincing any government to cut loose too much more money for asteroid searches. The silver lining of this cloud is that this might stop governments from cutting funding for asteroid searches as there have been many calls to do.
Even if we go to larger scopes, such small asteroids will still only be visible when they're relatively close to earth. It isn't practical to get orders of magnitude gains in sensitivity. There are new telescopes being put into service that will increase the number of objects we can find: http://pan-starrs.ifa.hawaii.edu/public/ but trying to get every rock down to a few meters probably won't happen.
I was just now reading BBC, and according to the BBC Nasa estimates the pre-entry weight to 10,000 tonnes. And releasing 500 kilotons of energy.
Sounds inflated...
The reports say " scientists have been concentrating their search for fragments of the rock around Chebarkul Lake, where a 6m (20ft) wide crater had been found following the strike....
A search of the lake bottom by a group of six divers on Saturday had found nothing; and it was thought the search would be delayed until the snow melts in the spring. "
- 6m hole in the ice, is quite small, and the fragment that hit the lake has to be much smaller than 6m, as the ice around it is little disturbed.
(which may explain why they found nothing)
The estimated size of the object, prior to entering Earth's atmosphere, has been revised upward from 49 feet (15 meters) to 55 feet (17 meters), and its estimated mass has increased from 7,000 to 10,000 tons. Also, the estimate for energy released during the event has increased by 30 kilotons to nearly 500 kilotons of energy released. These new estimates were generated using new data that had been collected by five additional infrasound stations located around the world – the first recording of the event being in Alaska, over 6,500 kilometers away from Chelyabinsk. The infrasound data indicates that the event, from atmospheric entry to the meteor's airborne disintegration took 32.5 seconds. The calculations using the infrasound data were performed by Peter Brown at the University of Western Ontario, Canada.
Comments
Thank goodness it wasn't misinterpreted as something other than a meteor .....
analyzed in due course. I've also heard 10 tonnes (which isn't anything like 17m diameter), but that might mean a fragment on the ground, not the original size.
Duane J
The instruments used for detecting asteroids can only see so faint. The detectors are pretty good already, with very high quantum efficiency so there aren't a lot of photons going to waste. To go fainter, you need bigger telescopes. But bigger scopes tend to have longer focal lengths, which means the field of view gets smaller so you cover less sky in any one image. That means you need more of them to get adequate coverage. In the grand scheme of things, the rock that hit Russia was very unusual. It was very large (compared to most that hit the earth), it hit land when 3/4 of the planet is water, and it hit a fairly densely populated area when most of the land is wilderness. Even then, the damage was relatively minor, and I think given the odds of it happening that you'll have a hard time convincing any government to cut loose too much more money for asteroid searches. The silver lining of this cloud is that this might stop governments from cutting funding for asteroid searches as there have been many calls to do.
Even if we go to larger scopes, such small asteroids will still only be visible when they're relatively close to earth. It isn't practical to get orders of magnitude gains in sensitivity. There are new telescopes being put into service that will increase the number of objects we can find: http://pan-starrs.ifa.hawaii.edu/public/ but trying to get every rock down to a few meters probably won't happen.
http://www.thisissomerset.co.uk/Green-space-slime-near-Glastonbury-baffles-nature/story-18183258-detail/story.html#axzz2LI4VykPT
I've seen this somewhere before......
I saw that movie as a child on TV on a Saturday afternoon in 1970. I don't think I slept well that night.
Sounds inflated...
The reports say " scientists have been concentrating their search for fragments of the rock around Chebarkul Lake, where a 6m (20ft) wide crater had been found following the strike....
A search of the lake bottom by a group of six divers on Saturday had found nothing; and it was thought the search would be delayed until the snow melts in the spring. "
- 6m hole in the ice, is quite small, and the fragment that hit the lake has to be much smaller than 6m, as the ice around it is little disturbed.
(which may explain why they found nothing)
http://news.yahoo.com/meteorites-risky-investment-201631149--abc-news-money.html
http://www.ebay.co.uk/itm/BOXED-LUNAR-METEORITE-SET-A-REAL-PIECE-OF-THE-MOON-/350672545368?pt=UK_Collectables_RocksFossils_Minerals_EH&hash=item51a5b66658
http://en.wikipedia.org/wiki/Dyatlov_Pass_incident
Very strange...
C.W.