Tag: near-Earth asteroid

Another tiny rock will pass Earth tomorrow

By Phil Plait | May 28, 2012 12:15 pm

[tl;dr: A small 5-10 meter asteroid will pass us tomorrow; it poses no danger to us.]

[UPDATE (May 29, 16:30 UTC): The JPL website for this asteroid has been updated – the rock passed us at the predicted distance of about 14,500 km from the Earth’s surface. The new numbers use 50 observations of the asteroid (the earlier orbit calculations used far fewer), so this looks pretty solid to me. As we knew all along, it was a close pass, but nothing to worry about.]

I recently wrote about near-Earth asteroid 2012 KP24, a house-sized (25 meter) rock. As I write this it passed us safely just a few hours ago, as predicted.

But thanks to scibuff and AsteroidWatch on Twitter, I just learned of another tiny visitor that will buzz past us tonight/tomorrow, May 29, at around 07:00 UTC (03:00 Eastern US time). Called 2012 KT42, this one is even smaller than KP24: it’s probably less than 10 meters across — about the size of a school bus or more likely a minivan. And it’ll be a close shave: though the orbit is still not nailed down, the nominal miss distance is about 14,500 kilometers (8900 miles). That’s a bit bigger than the diameter of the Earth itself.


[UPDATE (19:15 UTC): There’s more info on KT42 in on the Italian Remanzacco Observatory blog (h/t TredySas). There’s also a cool animation made from five exposures of it:

I’ll add more here if I hear anything.]


[UPDATE (19:55 UTC): No new info as such, but Alex Gibbs from the Catalina Sky Survey sent me this nice 4-tile mosaic of the discovery images of KT42, taken with the Mt. Lemmon 60" telescope:

Very cool!]


Bear in mind, it was only discovered last night, so the current orbit is preliminary. Many small rocks that pass close to Earth are discovered shortly before they breeze past us (and some not until after), so this is nothing out-of-the ordinary.

And since some people tend to get upset about these things, I’ll point out that as of right now, it looks like it will miss us. And even if newer observations show it hitting us, this rock is way too small to do any damage. At that size, it’ll break up in the atmosphere and make a spectacular light show, but not much else. This has happened countless times with asteroids this size, like the Peekskill meteor in 1992, or the more recent fireball over California last April. These can produce meteorites which fall to Earth, but the odds of getting by one are so small they’re basically zero.

Put it this way: the Earth has a surface area of more than 500 trillion square meters. Your surface area is less than 1 square meter (as seen from above). Those are pretty good odds you’ll be OK.

Another way to think about this is that rocks this size pass us all the time, but you never hear about them hurting us; that’s because they don’t! The smaller the asteroid the more common they are, but the less they can do to us. At this size, there’s no danger.

And as usual, I’ll point out that this discovery is a good thing! It shows we can find them, and that’s important. If we ever do discover an asteroid on a collision course that’s big enough to hurt us, the first step is to find it. And we’re getting better at that all the time.


Related Posts:

Small asteroid to buss Earth on May 28
A brief bit about asteroid 2012 DA14
No, asteroid 2012 DA14 will not hit us next year
Asteroid 2011 AG5: a football-stadium-sized rock to watch carefully
Updated movie of asteroid YU55, plus bonus SCIENCE
Asteroid 2007 TU24: No Danger to Earth

No, asteroid 2012 DA14 will not hit us next year

By Phil Plait | March 4, 2012 11:30 am

For the tl;dr crowd, let’s get this out of the way right away: asteroid 2012 DA14 is almost certainly not going to hit the Earth next February. And by "almost certainly", I mean it: the odds of an impact are so low they are essentially zero. This does not rule out an impact at some future date, but for now we’re safe.


So what’s the story?

A small near-Earth asteroid was discovered in late February by astronomers at the Observatorio Astronómico de La Sagra in Spain, less than two weeks ago. Designated 2012 DA14, it’s estimated to be about 45 meters (150 feet) in diameter, and has an orbit that is similar to Earth’s.



Its orbit is an inclined ellipse, tilted a bit compared to Earth’s orbit around the Sun (the positions of Earth and DA14 are shown for August of 2012 — I picked that randomly to make the orbits clear), and it spends most of its time well away from our planet. However, the path of the rock does bring it somewhat close to the Earth twice per orbit, or about every six months. The last time it passed us was on February 16 – two weeks ago — when it was about 2.5 million km (1.5 million miles) away, equal to about 6 times the distance to the Moon. That’s usually about the scale of these encounters — it misses us by quite a margin.


February 2013: a close shave

Next year, on February 15, 2013, DA14 will actually get pretty close to Earth. It will pass us at a distance of about 27,000 km (17,000 miles) — well beneath many of our own orbiting satellites! To the best of my knowledge, this is the closest pass of a decent-sized asteroid ever seen before the actual pass itself.

However, let’s again be very clear: it will miss. In astronomical terms, 27,000 km is pretty close, but in real human terms it’s a clean miss.

[UPDATE: The rt.com article I linked below has changed substantively since I posted my own article here. They have attributed their quotations more clearly, and have taken out most of the more breathless rhetoric. I applaud them for doing so, though I wish they had been more clear in the first place.]

Unsurprisingly, though very irritatingly, I’ve seen a lot of websites writing about this as if the asteroid will hit. For example, rt.com has a very confused article about DA14 claiming it will somehow both miss us and hit us:

The rock’s closest approach to the planet is scheduled for February 15, 2013, when the distance between the planet and space wanderer will be under 27,000 km (16,700 miles). […] With the asteroid zooming that low, it will be too late to do anything with it besides trying to predict its final destination and the consequences of impact.

Blechh. They write that in a way to make an impact seem likely, but that’s not the case at all! I’ve seen several other websites making similarly contradictory or confused claims (Note:I originally included this SFBay article as an example. It’s not confused, but by using the phrase "potentially fateful day" it struck me as exaggerating the fear). The rt.com article even comes right out and says "NASA confirms… [DA14] has a good chance of colliding with Earth". This is simply not true. I’ll note they don’t actually give a reference to that, so it’s not clear who, if anyone, actually said that, or where they got that information. Either way, it’s wrong.


The fuzzy future

So we’re safe for now. But what about future passes?

That’s harder to say. Predicting where an asteroid will be at some future time depends on a lot of things, including how good the observations are now and how long we’ve been watching it. When we observe an asteroid with a telescope, we can measure its position, but not with perfect accuracy. The Earth’s atmosphere blurs the image a bit, and other factors make it impossible to get an exact measurement. So we observe it many times, over as long a period as possible, to hammer down those uncertainties.

There will always be some small amount of fuzziness to the orbit of an asteroid, though, and the farther ahead in the future you look the bigger that fuzziness gets. For next year, we know the orbit of DA14 well enough to know it’ll miss, but for future orbits it’s harder to say.

As things stand, right now the JPL website lists the next close pass as February 2020, but we don’t know the orbit well enough at this moment to know how close that pass will be*. As things stand, the odds of an impact even then are very, very low (like, 1 in 100,000 — less than your odds of getting hit by lightning in your lifetime). We can’t technically rule it out just yet because, again, the orbit isn’t known well enough to look that far into the future. Of course, astronomers are observing the asteroid right now, and will continue to do so. No doubt we’ll have better orbital information pretty soon.


Keep watching the skies!

So again, because I can’t say this strongly enough: asteroid 2012 DA14 is not an impact threat for February 2013. However, we definitely need to keep our eyes on this guy to see if it poses a threat at some future date. If it does, then you can be sure you’ll be hearing about it from me, and from other websites too. But make sure you find reliable websites. Too many are too ready to breathlessly report this as doomsday when it’s anything but.

So, at least for February 2013, we can safely say:


* I’ll note the European NEO-DyS group uses different mathematical techniques, and they don’t even list that date as a near pass. Instead, they say it’ll be six months later, in September. Again, this shows that given our current observations of DA14, predicting its position that far in the future is very uncertain.


Related Posts:

My asteroid impact talk is now on TED!
Just to be clear: asteroid YU55 is no danger to Earth
Media FAIL *again* (HuffPo and Apophis edition)
Debunking doomsday

Another tiny rock will whiz past us tomorrow

By Phil Plait | February 8, 2011 10:04 am

On February 9 at around 19:30 UT, a small asteroid the size of a car will cruise past the Earth, missing us by a distance of about 100,000 km (60,000 miles). By astronomical standards that’s pretty close (about a quarter of the way to the Moon) but it’ll miss us for sure.

Called 2011 CA7, it was discovered earlier this month. The short notice is not too surprising, given that it’s at a very faint magnitude of 20 — you’d need a big telescope to be able to see it at all! Even at closest approach it’ll be magnitude 17, less than a ten-thousandth as bright as the faintest star you can see with your unaided eye.

There is some small uncertainty by exactly how much it’ll miss us; the orbit isn’t precisely determined yet. According to the JPL small-body data browser, the minimum distance 2011 CA7 will pass us is 93,000 km (58,000 miles), and the maximum is 114,000 km (71,000 miles), but the most likely distance is 103,000 km (64,000 miles). These numbers may change as time goes on, but the important thing to note is that it will miss us.

Given the brightness of the object, it’s obviously pretty small, probably around 3 meters in diameter, or about 10 feet. That’s a little bit bigger than 2011 CQ11 which blew past us last week, but not significantly so. Even if it were to hit us it would certainly disintegrate high up in the Earth’s atmosphere and at worst rain down a few rocks; that sort of event happens several times a year somewhere on Earth, if that makes you feel any better. In other words, it’s relatively common and presents very little danger. Interestingly, this little guy has probably passed us many times in the past, but this is the closest encounter yet (which makes sense; it’s so small and faint it’s only when it gets close that it can be seen at all).

This is an interesting rock. Its orbit goes from roughly the orbit of Venus out to that of Mars, and that means it spends most of its time in near-Earth space. I imagine over a long period of time, maybe millions of years, an impact is inevitable — but again, something this small will make a pretty light show but present very little real danger. In that picture above you can see the orbit in teal; the Earth and the asteroid are to the lower left. On this scale — hundreds of millions of kilometers across! — the rock looks like it’s right on top of us, but 100,000 kilometers is a long way off in real terms. A miss is a miss.

I haven’t seen any imaging of it yet but I’m keeping my eyes open, and hopefully we’ll get some nice pictures of this. Stay tuned!

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