A NASA news item today explains how scientists are piecing together what happened, using infrasound sensors operated by the Comprehensive Test Ban Treaty Organization (CTBTO).

Their purpose is to monitor nuclear explosions. Infrasound is a type of very low-frequency sound wave that only elephants and a few other animals can hear. It turns out that meteors entering Earth's atmosphere cause ripples of infrasound to spread through the air of our planet. By analyzing infrasound records, it is possible to learn how long a meteor was in the air, which direction it traveled, and how much energy it unleashed. The Russian meteor's infrasound signal was was the strongest ever detected by the CTBTO network. The furthest station to record the sub-audible sound was 15,000km away in Antarctica.

Video above: Listen to the infrasound recording, sped up 135x into the range of human hearing. The video comes from the Comprehensive Test Ban Treaty Organization's YouTube channel.

Peter Brown, University of Western Ontario Professor of Physics, analyzed the data and determined that the asteroid was about 17 meters in diameter and weighed approximately 10,000 metric tons.

"It struck Earth's atmosphere at 40,000 mph and broke apart about 12 to 15 miles above Earth's surface. The energy of the resulting explosion exceeded 470 kilotons of TNT." For comparison, the first atomic bombs produced only 15 to 20 kilotons.

Based on the trajectory of the fireball, analysts have also plotted its orbit. "It came from the asteroid belt, about 2.5 times farther from the sun than Earth."

More: What Exploded over Russia? [NASA Science].

Tonight we should see the peak of this year's Geminid meteor shower. I wrote about the weird scientific mystery surrounding this particular meteor shower yesterday, and Miles O'Brien wrote a great feature on it for us today.

In the comments on my post yesterday, reader Clayton Yarbrough mentioned that meteors have an effect on radio signals, and I wanted to follow up on that, because it's a pretty cool phenomenon. Basically, meteors can allow you to send radio signals farther than is normally possible. In the video above, you can watch 7th grader Jeffrey Kelly interview a ham radio operator who explains how this works. But first a little background.

Radio waves travel through the air. You are, of course, aware of this. But there's also a limit to how far they can travel. Partly, this is because the radio waves move in what could be characterized as a straight line, but the planet Earth curves. To get around that bend in the horizon, ham operators frequently bounce their signals off a part of Earth's upper atmosphere, called the ionosphere. What makes the ionosphere special? It's ionized, meaning the particles it's made of are electrically charged. That should give you all the background you need to follow along with the video.

Read more on skywave communications (bouncing signals off the ionosphere), and meteor scatter communications.

I am talking about the Geminids Meteor shower which emanates from the Gemini constellation. Finding it should not be hard - even for a night sky newbie. Find Sirius. Up and to the right will be Orion's Belt. Up a little higher to the left will be Gemini. The meteors will emanate from there (astronomers call this the radiant).

NASA is running a chat during the shower and will also be sending out a live image from the Marshall Spaceflight Center on their Ustream channel tonight. This is nice if you would prefer to stay warm and in your jammies! More on all of this here.

My friends at Universe Today also have a good Gemind viewing guide.

There are, of course some apps for this if you have trouble navigating in the dark. Star Walk is a good one for the Apple Nation. I cannot personally vouch for anything Android, but I would guess the Google Sky Map would be a good place to start.

They show goes on from about 9:00pm until 4:30am wherever you happen to be. Peak viewing should be around midnight to 1:00am

To get some deeper gouge, I Skyped the folks at AtronomyNow.com. I spoke with their night sky consultant, Mark Armstrong. You can watch, or read the transcript, or both!

Miles O’Brien: So, let’s talk about the Geminids. First of all, what are they?

Mark Armstrong: Geminids are streams of small particles, maybe dust or leftovers from a comet. It’s usually--what happens with a comet is it orbit around the sun and it leaves a stream behind it of dust so small meteoroids. And meteor showers are commonly encountered every year. Time and time each year, the earth is intersects with the stream. And small particles hit the upper atmosphere burn up say 50 to 80 miles up in the atmosphere and that produce trails of lights in the sky which is what we call meteors.

Miles O’Brien: And we’ve heard about the Leonids and Perseids and the Geminids. Compared to the others, how does this particular night time show rate?

Mark Armstrong: At the moment, Geminids is the best show of the year. It’s the richest of the year so from a casual observer or a series of them, they got to see more meteors in the sky with this shower. Maybe 10 years ago, the Leonids was the richest shower. Some of the streams and clumpy so every now an then, when the earth hits the stream, there’s enhanced activity but the Leonids have died off a bit. And now the Geminids, we have perhaps 50 to 80 meteors an hour from a reasonable site. The Geminids is the best one of the year.

Miles O’Brien: Fifty to 80 per hour. That sounds pretty good. That’s like shooting fish in a barrel. We should all be able to see something if we’re looking in the right place, right?

Mark Armstrong: Absolutely yeah. You’re guaranteed to see one a minutes at least (assuming the sky is clear, obviously). There’s no moon this year -- the moon is new so there’ll be no moonlight to wash out the fainter meteors. This year has been pretty bad for meteor observers with the moon interfering in a lot of cases, but the Geminids are moon-free so there’s every reason to get out there. And the only difficulty -- not difficult but it’s going to be very cold. December at night is obviously very cold in the northern hemisphere so you have to wrap up warm and make sure you stay warm.

Miles O’Brien: Stay warm and stay focused. Which part of the sky shall we be looking at and when?

Mark Armstrong: It’s the constellation of Gemini, the twins so these two bright stars, Castor and Pollux which is to the northeast of Orion - that’s where they all appear to emanate from. So, the Gemini radiant is high enough in the east when the sky gets dark. It culminates at its best from the U.K. at least about 1 A.M. (GMT). So as long as you look towards the constellation of Gemini, the best thing is to look about 50 degrees high and perhaps 30 degrees either side of the radiant. Don’t actually stare directly at radiant. The radiant is a few degrees north of Costa which is the fainter of the two stars a more novelly in two stars which the main stars, the twins, in Gemini. So look slightly north of Costa. But if you look to about 30 degrees either side, if you could hold your fist out at arms length, the width for the fist is about ten degrees.

Miles O’Brien: So, you mentioned the peak times in the U.K. In the continental U.S., it sounds like the peak will occur before night fall, is that right?

Mark Armstrong: No. The peak is right about midnight in the United States. So, about that time the Geminids will be -- went up so it’s quite a favorable peak for the U.K. and not too bad for the U.S. either.

Miles O’Brien: So it should be a good night pretty much from all the way from Europe, all the way into the U.S. and you don’t need a lot of fancy optics, do you?

Mark Armstrong: No, no. You just use the naked eye. Often, it’s good if you observe in groups. That’d be a bit more fun. And if you want, you can just look for fun maybe an hour or two hours. Always take a break so have a hot drink with you. Don’t just stare for hours and hours because you’re never -- you’ll lose concentration. So as soon as you observe them like two hours, then take a break, relax and then go back to it. You can if you want to try and take notes of -- if you see a bright meteor. The Geminids are quite good because they are quite -- as meteoroids go, they’re quite substantial because they’re definitely from an asteroid rather than a comet so they tend to be slower, a bit more resilient and so they can be very bright. So, there’s a good chance of seeing some bright events. And if you see, those you can -- as you track them, perhaps try and take a note of their magnitude. So, there are -- serious observers can make good difference to science or you can just observe for fun.

Miles O’Brien: So binoculars really aren’t going to help you, probably make it harder to see? Is it possible with consumer level gear to get any sort of images, movies, stills or otherwise?

Mark Armstrong: Yeah. With a movie camera, just point a camera. Even stills, you can just open a shot up for five seconds or maybe a minute. You have to be careful that the lens doesn’t fog up in a cold weather. But sure, there are people have obtained good images of the meteor - Geminids or whatever meteor before. And you could also get movies as well which are very -- especially at these bright events, they are very spectacular.

Miles O'Brien: There’s something magical about being out in the night sky and seeing a meteor streaking across the sky. What is it about it, you think, that captivates us?

Mark Armstrong: I think it just reminds you of the wonder of the night sky. Most of the time, the stars aren’t changing, galaxies aren’t changing, obviously the planets come and go, get brighter, get things but a meteor is something -- it shows that the solar system is an active place and it’s just a wondrous thing to see a fireball. It’s possible that there might be little fireballs which could be as bright or brighter than the Venus. Some years ago, I think it was the Geminids. There was enhanced activity and there was lots of fireballs and that was a wonderful night. It’s not like you would see anything that should but the Geminids are well-known for a high proportion of bright events. It just shows that the solar system in action really.

Miles O’Brien: And for me, it’s a reminder that earth, our home, lives in kind of a dangerous neighborhood. There are a lot of rocks out there that could clonk us.

Mark Armstrong: Yeah indeed. If a meteoroid makes it through the atmosphere and hits the earth, that’s a meteorite and there are plenty of examples of those that have been found. It’s unlikely you’re -- this will happen this time but -- and then the bigger picture with the deal around asteroids and the comets that there’s very faint possibility but it happened before to earth where we’ve been hit, the Tanguska event in the early 20th century. So there’s always that possibility that one might have our name on it but let’s hope we’ve got many years ahead of us.

Miles O’Brien: Well, if you’re skeptical about all that, just go ask a dinosaur about it, right?

Mark Armstrong: Absolutely.

# # #

Previously on Boing Boing: "Weird meteor shower to peak tomorrow night"

Photo: Shutterstock]]> http://boingboing.net/2012/12/13/geminids-meteor-shower-how-to.html/feed 14 http://boingboing.net/2012/12/12/weird-meteor-shower-to-peak-to.html http://boingboing.net/2012/12/12/weird-meteor-shower-to-peak-to.html#comments Wed, 12 Dec 2012 19:39:33 +0000 Maggie Koerth-Baker http://boingboing.net/?p=200032

The Geminids are one of the big deal meteor showers that happen every year. In fact, they're regarded as one of the most reliable and impressive. They're also a little strange.

Most meteor showers happen when Earth and a comet cross paths, slingling rocks, dust, and debris from the comet's tail into our atmosphere.

The Geminids are one of the big deal meteor showers that happen every year. In fact, they're regarded as one of the most reliable and impressive. They're also a little strange.

Most meteor showers happen when Earth and a comet cross paths, slingling rocks, dust, and debris from the comet's tail into our atmosphere. The sudden influx of shooting starts that results is a highly noticeable event and humans have been recording them for millennia.

The Geminids are different. They sort of just appeared, seemingly out of nowhere, back in 1862. And it wasn't until the 1980s that scientists were finally able to identify the thing that was producing them. At which point, ish got weirder.

That's because the object, known as 3200 Phaethon, is really confusing. It doesn't seem to be a comet. At least, not a normal, healthy, functioning comet. It doesn't even have a tail. In fact, at this point most scientists think it's probably an asteroid, which then leads to still-yet-unexplained question of where all the meteors come from. Asteroids, after all, do not typically accumulate tails of small rocks. So far, the best guess has to do with 3200 Phaethon's orbit, which over the course of about a year and a half takes it closer to the Sun than Mercury and then back out further from the Sun than Mars. Those wild temperature swings might lead to the asteroid cracking and throwing off dust and debris, which then becomes meteors. But, as a NASA info page pointed out in 2010, that explanation doesn't totally cut it.

The amount of dust 3200 Phaethon ejected during its 2009 sun-encounter added a mere 0.01% to the mass of the Geminid debris stream—not nearly enough to keep the stream replenished over time.

According to the International Meteor Organization, you can expect the Geminids to peak tomorrow night, around 5:30 pm, Central Time. But this is a big shower, so you're likely to see something even if you can't hit the exact peak.

Also: While you're watching for meteors, also keep an eye out for an upcoming feature here by Miles O'Brien, which will delve into the latest in Geminid science!

Read the 2010 NASA info page on the Geminids and an earlier NASA piece that describes a different theory for their origins.

Make use of The Bad Astronomy guide to meteor watching

Image: Geminid Meteor. Just one., a Creative Commons Attribution (2.0) image from tydence's photostream

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(Photo, via Wikipedia: "Leonid Meteor Storm, as seen over North America in the night of November 12./13., 1833. Source, E. Weiß: "Bilderatlas der Sternenwelt"; Published 1888)

The Earth is hurtling through mostly empty space at nearly 70,000 mph. But space is only mostly empty. Throughout the solar system is debris left behind by comets, colliding asteroids, and even dust from interstellar space. When the Earth hits these things - at 70,000 mph - it puts on a nice show.

You can see the show any time of the year. Just find a dark moonless sky and stare up for a while. You'll eventually see the quick streak of a shooting star. That "shooting star" was what happens when one of these tiny dust-sized pieces of debris gets in the way of the earth. It burns high in the atmosphere. Very very occasionally the earth will run into an even larger piece of debris.

The best I ever saw in my life was when I was sitting on a beach in Hawaii and noticed a bright light behind me, turned around, and saw a huge bolide split multiple times in the air before disappearing behind a volcano behind me.

These days they are often caught by security cameras or by whoever happens to have a video camera in their hand at the time.

Some parts of the solar system are dirtier than others, and right now the Earth is plowing through one of the dirtier ones. We are plowing right through the orbit of a former comet, and that orbit is full of dust and small rocks sputtered out by the comet over centuries. The comet has lost so much debris, in fact, that by now it appears as a barely distinguishable rocky asteroid quietly orbiting the sun.

If you want to see shooting stars and see a lot of them, now is a good time to get outside and do it.

When? Where?

There's a little bit of bad news here, that you can understand just by thinking about how the direction Earth is moving through space. View from the north pole, the Earth goes counter-clockwise around the sun. So imagine, as we did a few days ago, that you are looking down on the Earth and that the Sun is off at the 6 o'clock position. If you were standing on the Earth at the 6 o'clock position the sun would be straight overhead; it would be noon. If you were standing on the Earth at the 12 o'clock position it would be the middle of the night: midnight. Since the Earth also rotates counter clockwise, if you are standing at the 3 o'clock position you see the Sun on the horizon, but soon you will rotate into darkness: sunset. And at the 9 o'clock position you will be experiencing sunrise. The 9 o'clock position is also special because it points in the direction that the Earth is travelling around the sun. In other words, if you are standing on the Earth and the sun is rising and you point straight up (and you don't live too close to the north or south pole!) you will be pointing in the direction that the Earth is travelling.

The Earth is slamming into the cometary debris as it travels, so the place to look is in the direction of travel. Straight up. Sunrise. Sunrise is, of course, too bright, so you're actually better in the hours before sunrise when it is still dark. The Moon and Jupiter will have set (don't miss Venus and Saturn, too, but we'll talk about those next week), and the skies will be dark. (The debris itself is moving too, actually, so this rotates the impact point around enough that the actual best time is more like 2am, but any time after the Moon sets and before the Sun rises should be fabulous).

What will you see? No one ever knows precisely what a meteor shower will show, or even precisely when it will peak. The current one is expected to be good tonight, better tomorrow night, and fade quickly. At its peak you could see a shooting star every minute from a nice dark clear site. If you're lucky, you'll see one split into pieces and color the skies.

It's the end of life for the little piece of cometary debris that first coagulated out of the interstellar cloud of gas and dust more than four billion years ago. It's been a long ride: billions of years out in the asteroid belt, finally heated and ejected from a comet, a lonely flight through empty space, and then a firey death as the Earth slams into it. Don't you want to be there to see its last ride?

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