The Geminids: A Fiery Death

Leonid_Meteor_Storm_1833.jpg

(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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    1. Even during a major meteor storm, the density of the dust is pretty low, so major impacts with satellites are uncommon. It is a legitimate concern, though.

  1. Ops. Please forgive the typo. Rewind: Dear Mike, do you think the video http://bit.ly/7m9U6 you linked in this article is *real*? Is there any reference about the episode? Thanks, Andrea from Italy

      1. Thanks mr. skeleton and Mike for confirming the second video is not true. Quite hilarious indeed, but for who can appreciate it is a fake, so I’m happy the trick has been unveiled in these comments. Forgive me for being so dull and vulcan-logical, thanks again to Mike for his posts and all his work as the leading web 2.0-astronomer!

  2. Quick calculation: A 50mg rock fragment (about the size of a grain of rice) traveling 70,000 mph would impact with about 25,000 joules of kinetic energy (1/2 mv^2).

    How much damage would that do to a spacecraft or a spacesuit?

    1. Well, per http://en.wikipedia.org/wiki/Muzzle_energy, a .50 caliber heavy machine gun would have a muzzle energy around 15 kJ – so a collision at that speed would have close to twice the force of a point-blank shot with a heavy machine gun; equivalently that’s about 6 – 8 times the power of a point blank shot with a standard 30-06 hunting rifle.

      So, at a guess, a spacecraft or spacesuit would not hold up very well.

  3. Just found out the other day that “Geminids stand apart from the other meteor showers in that they seem to have been spawned not by a comet, but by 3200 Phaeton, an Earth-crossing asteroid.”

    http://www.space.com/spacewatch/geminid-meteor-shower-skywatching-tips-101210.html

    Now and then (but rarely) showers include -really large- objects. But in my experience, you just never know when you might see one, and making a habit of watching the sky is the only way to up your ‘luck’. I’ve seen two (amazing) bolides and one green fireball that way. And (long ago) something literally aflame drifting slowly, straight down from the sky for over a minute.

    For added reader enjoyment, here’s a video of the August 10, 1972 Grand Teton meteor

    and an APOD picture with many more links

    http://antwrp.gsfc.nasa.gov/apod/ap090302.html

  4. I imagine at velocities like that our meteorite and a bit of suit would be vaporized. I am betting that unless it is a hose or maybe the faceplate strike it will be little more than a slight bump maybe unnoticed until the suit is inspected since most of the energy is dissipated in gas form, a tiny meteorite could not be expected to be as efficient at penetration as a well engineered 12.7mm bullet. Remember that the person holding a gun absorbs more energy than the person being shot. Bullets are so destructive because of design not simple mathematical energy transfer.

    I like meteorites because you can use the ionized trails to reflect long range transmissions at VHF frequencies which are mostly line of sight range.

    1. I too was thinking that the 50mg meteor would have to maintain its integrity to do real damage, and that the energy would be dissipated as it vaporized.

      But, imagine a 1 gram meteor (500 kJ), with a high metal content.

  5. “That “shooting star” was what happens when one of these tiny dust-sized pieces of debris gets in the way of the earth. ”

    Dust-sized?

  6. 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?

    Beautiful writing, Mike. Thanks for the reminder to check out the show.

  7. We spent about an hour watching last night (Monday morning) and saw about 30 meteors in a little over an hour. There were some pretty good ones too!

    Tonight should be even better, hoping for clear skies.

  8. Question: Dan – who posted the uTube video of the daylight fireball of 1972- was somehow able to find online information about this. Is there a formal registry of such events?

    I witnessed one in central ohio on an afternoon probably in the spring/summer of 1974. I would like to know if anyone caught that one on film.

    One interesting aspect is that I was driving south, and it was so bright that even in full daylight, and even thought it was to the east, almost at right angles to my path, I noticed a sudden increase in light, which attracted my attention to it.

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