Ecogirl woke me up at 6 am this morning (February 15th 2013) to tell me about the fireball over Russia this morning and the casualties that resulted. My immediate reaction was “Oh no, I hope this isn’t related to 2012 DA14!” the asteroid that will do a record close fly-by of the Earth later today. After spending an hour weighing up the internet reports I’m fairly convinced they aren’t related – this is a truly cosmic coincidence! So because like me you were looking for information about what’s happening, here’s a top ten list I’ve put together along with some help from some other great blog posts (here, here, here).
10. What time did the Russian meteor hit this morning? 3:15 am UTC (essentially GMT in gold old fashioned terminology!) converts to 10:15 pm eastern. So this one happened while most of N. America was either in or getting ready for bed!
9. What caused all the damage? Was it the meteor exploding? As far as we can tell from the video footage, the meteor did break in two, but there wasn’t a cataclysmic single explosion event in the trail (although this is still an “air burst“). Most of the early evidence suggests the boom was from the “sonic boom” as the meteor reached down to roughly 40,000 feet in the atmosphere (reports suggest small pieces seem to have hit the ground as well) while travelling much faster than the speed of sound. Note for multiple pieces it’s reasonable to have a number of booms, so the reports of their being multiple parts to the boom are quite reasonable. Better analysis is still needed. Update: the air burst is now being quoted as occurring at around 100,000 ft, much higher than anyone initially thought. That means the meteor was much bigger than originally thought, and the shockwave probably did have something to do with the explosion. Models are still poorly constrained, but the explosion could have been equivalent to several Hiroshima bombs (50kT). That means the shockwave wasn`t just a sonic boom either. The models will definitely improve over the next few days as more data becomes available.
8. Just how fast was it travelling and how big was it? Video footage is difficult to interpret, but estimates are coming out that it was travelling around 50,000 kph when it hit the atmosphere. Based upon the size and brightness of the trail it’s been estimated that the meteor was probably around 10 tons – but remember it’s very early in terms of data analysis. It will take a few days to get a really good idea of what happened. Don’t trust everything you see right now, and the flaming impact crater videos on youtube are totally fake. Update: NASA estimates have placed the mass in a much larger range – perhaps as large as several thousand tons!
7. I’ve never heard anything during the meteor showers I’ve seen. How come this one made a sonic boom? Most meteor showers are from very small (cm size) objects hitting the very tops of the atmosphere. They burn up very quickly, very high up (80-130 km or 260,000+ feet). You all know that thunderclaps can’t be heard from large distances, and it is the same with the sonic booms from objects that are very high in the atmosphere. Today’s fireball, being caused by something in the range of 10 tons in mass, meant it reached much further into the atmosphere (pieces likely impacted). Update: As you can see from above, this object seems to have been far larger than anyone initially anticipated! I don`t think there is much doubt that it wasn`t just a sonic boom that was heard.
6. Did the russian military shoot it down? No. While it’s almost certain this event was at least seen by the military once it got lower in the atmosphere and produced an ion trail, it was travelling too fast for them to intercept. Anyone remember how difficult it is to design a missile defence shield? Same problem here.
5. How often do these things happen? Should I be worried? More often than you’d think. Objects 3-4m in diameter hit the atmosphere about once a year, and experts are estimating that the Russian event is a 1 in 5 year to once a decade event. Military satellites sent up decades ago to track missile launches surprised everyone when they discovered far more meteors hitting the atmosphere than anticipated. Should you be worried? Well impact events obviously happen and we need to look for potential impactors, so while I don’t think you should worry, yes it’s something you should know the risks of – I’ll say more about this at the end! Update: the revised mass estimates mean this is at least in the once a decade range, maybe longer!
4. What’s the link between asteroid 2012 DA14 and the meteor this morning? As far as we can tell right now, the impact trajectory of the russian meteor is completely different to that of the asteroid (moves South to North). If you run the clock back in time that means the meteor and asteroid just get further and further apart – so no, it really doesn’t seem like there is any link. Of course, without knowing that, when I was woken up this morning I was initially quite worried until I saw the news reports!
3. How close is the asteroid 2012 DA14 going to get to the Earth? Will it enter the atmosphere? At around 2:30 Eastern this afternoon it will pass with 28000 km of the surface of the Earth. That’s about 2.5 times the diameter of Earth, so while it’s very close by astronomical standards it’s still a long way from the atmosphere. Update: passed by… no worries!
2. What would happen if 2012 DA14 hit the Earth? And will I be able to see it? I’ll say it again – it isn’t going to impact – don’t worry! But at 130,000 tons, it would be far, far more devastating than the Russian meteor this morning. We’d be talking about something akin to a megaton nuclear weapon – hundreds of times more powerful than Hiroshima or Nagasaki. Thankfully that isn’t going to happen, but if you want a good comparison, take a look at the Tunguska event.
1. Is there anything that can be done to stop this an impact like this? What can we do? We need to know what’s out there first, and that means better monitoring. There are probably a few thousand asteroids out there that are potentially hazardous. Astronomers are working on a number of telescopes that will survey the sky on a regular basis. Although objects that come at us from the direction of the Sun are very hard to spot. Once we’ve got a really good idea of what’s out there then we can start to talk about how we can stop any collisions (and calling Bruce Willis isn’t the best course of action folks!). Of course, this is all within the limits of the budget cuts that everyone is facing because of the financial crisis!
Apologies that I couldn’t get this posted sooner! Sometimes work gets in the way of news! Update: It`s great to see how things unfold as better data comes in. Everyone should be really careful about reporting initial data, even I was taken in by the sonic boom argument. Will no doubt hear a lot more over the next few days.