Last week, the asteroid 2005 YU55 passed by the Earth. Lots of observations were made, including using the Goldstone radio telescope in California. I wrote about how this works last week. NASA just released a new video showing an updated animation containing 28 frames, showing YU55 rotating as it swung past us:
That’s pretty nifty. Mind you, this isn’t an image like an optical telescope would make, but instead is a constructed 2D representation using what’s called the Doppler Delay technique; that’s why it looks like it’s illuminated from the top. That’s not real; read Emily Lakdawalla’s excellent writeup to get more info on how that works.
However, from looking at the animation you can see several features, including some broad depressions (YU55 is about 400 meters across, so some of those dips are the size of football fields). There are also several bright spots which I find interesting. Read More
The eyes of many astronomers — and the eyes of their telescopes — were aimed at the asteroid 2005 YU55 a few days ago, when it passed the Earth at the relatively close distance of about 320,000 km. One of those eyes was actually in space as well: NASA’s Swift satellite. This spacecraft was designed to look at the sky in the ultraviolet, X-ray, and gamma rays, all high-energy forms of light emitted by the most violent events in the universe: exploding stars and gamma-ray bursts.
But the Sun emits UV, and rock can reflect this light, too. So Swift observed YU55 as it passed us, and got this very interesting footage of it, what I think is the coolest I’ve seen so far:
[You can also watch it on YouTube if you prefer.]
Pretty neat, and by looking at the rock at different wavelengths, we can learn about its structure and composition, too.
But I know what you’re thinking: in the video, why did YU55 curve around as it moved? As it turns out, I was expecting this when I watched the video! What’s going on*?
The asteroid is in elliptical orbit around the Sun, but over the short period of time covered by this video — about 20 minutes — it’s essentially moving in a straight line. The reason the path is all bendy is because Swift itself is in motion! Swift orbits the Earth, circling us once every 90 minutes or so. As it moves around us, its viewpoint is changing, and that motion is reflected in the asteroid.
I wasn’t going to post anything else about asteroid YU55 until the images became available, but NASA just put up a video explaining a little bit about how they plan on getting observations of the sucker as it flies past us over the next couple of days:
Just to clarify a bit: those radio telescopes can be used like radar guns, sending out short pulses of focused radio waves. These pulses are aimed at the asteroid and move at the speed of light, hitting the rock and bouncing back. Since we know the speed of light very accurately, we can measure the time it takes a pulse to get to the asteroid and back, multiply it by the speed of light, and get the distance (for example, if it takes 5 seconds, and the speed of light is 300,000 km/sec, that means the pulses traveled 1.5 million km round trip… so don’t forget to divide by 2 to get the distance to the rock).
But there’s more! The individual pulses can be timed very accurately as well, so that the shape of the asteroid can be determined, too. If there is a bump on the asteroid, like a hill, then a pulse hitting that won’t travel quite as far as a pulse that hits a crater. It gets back sooner, and this can be measured. The spatial resolution of this method at the distance of YU 55 will be about 4 meters, so they’ll be able to make an image that’s about 100 pixels across of it.
[UPDATE: In fact, this image here of YU55 was released like two minutes after I originally posted this article. It was taken using the Goldstone radio telescope in California on November 7, when YU 55 was still 1.4 million km (860,000 miles) from Earth!]
[Update 2: Emily Lakdawalla wrote a great discussion of all this on her blog last year; I highly recommend reading it!]
Not only that, but the wavelength of the pulses are very accurately known, too. If the asteroid is spinning, then the wavelengths of the returning pulses will be altered, like in the Doppler Effect. So all in all, we can determine the rock’s size, distance, shape, and rotation, just by painting it with radar.
That’s pretty good for a species that doesn’t even have to leave the ground. Still, we’d learn a whole lot more by actually going to these things. And we’ve done that, too. See Related posts, below.
We’re clever, we humans, when we want to be.
Image credit: NASA/JPL-Caltech
Tomorrow, November 8, the 400-meter-wide asteroid 2005 YU55 will glide past the Earth, missing us by a very comfortable margin of 320,000 kilometers (200,000 miles). This distance is three-quarters of the way to the Moon, and is in fact so far that you’ll need a decent telescope to see it at all.
However, I’m starting to see rumors that the asteroid will have an effect on us. I expected this — it happens every time there’s a decent-sized rock that whizzes past us. That’s why I wrote a post about it a few months back, but I want to follow up on it. Why? I’m getting wind of some folks worried about YU55, including a couple of notes on Twitter saying there are people blaming Saturday’s earthquake in Oklahoma on YU55!
Let me be clear: no asteroid, YU55 or otherwise, can cause earthquakes as they pass. Even Ceres, the largest asteroid in the solar system, would have to practically skim the top of our atmosphere to have any real effect on us. YU55 is dinky, and will miss us by 25 times the diameter of the Earth!
And c’mon: why would it shake up Oklahoma? Japan, Turkey, Chile, California — there are dozens of seismically active spots on Earth that are more prone to earthquakes. Someone claiming an asteroid causing one in Oklahoma should set off alarm bells in your head*.
I’m sure there will be other claims as well. People will squeeze whatever they can out of this event. I saw it happen in 2008 when a similarly-sized rock, 2007 TU24, passed by us at a distance of more than half a million kilometers. Things got so ridiculous with the doomsday scaremongering back then that I made a video to alleviate fears. I’ve embedded it here; all you need to do is replace "2007 TU24" with "2005 YU55", and the 530,000 km miss by 320,000 kilometers, and all the stuff I said back then still applies.
And for those of you still prone to worry, let me add this: I was right. And when was the last time an end-of-the-world doom crier was right?
Let me give you a hint: Never.
Not that this will stop them. There’re two things I know for sure: they’ll never admit they were wrong, and there will always be something else. The next asteroid, the next full Moon, the next star they think will explode, a pole shift, whatever.
As long as people aren’t familiar with the reality of the situation, there will be fearmongers to take advantage of the situation. That’s a big reason I do what I do, and why I have to do what I do.
Image credit: NASA/Cornell/Arecibo
* You’d think at least they’d claim it was last week’s solar flare that did it; after all, it’s Oklahoma, where the solar wind comes sweepin’ down the plain…
On November 8th of this year, the 400-meter-wide asteroid 2005 YU55 will pass the Earth, missing us by the comfortable margin of 325,000 kilometers (200,000 miles).
While this is the largest asteroid (that we know of) to swing past us for the next 17 years or so, YU55 is not an immediate threat to Earth. Its orbit does bring it close enough to our planet that it’s been deemed a potentially hazardous asteroid, but the orbit is well-enough known that we can rule out an impact for at least the next century. That’s long enough for me personally to not be concerned.
I’ve seen some small amount of buzz on the usual conspiracy sites about this asteroid, and I do see some folks trying to play this up a bit (search on "YU55 doomsday" for example), but fear-mongering chatter is surprisingly low for this event. I expect that by this fall you’ll be seeing breathless YouTube videos accusing NASA of covering up a imminent impact — and I don’t say this blithely; it’s happened before. Remember asteroid 2007 TU24? No? That’s because nothing happened, despite the claims of panic-promoters.
As you can see in this JPL animation below, in November YU55 will miss us by a cosmic mile as well (click to embiggen and get a clearer animation):