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Why can't we prevent asteroid strikes?

Asteroids: Yet more evidence that (as a society) we aren't very good at prioritizing preventative measures against long-term risks. Maggie

What are the chances of a large meteor destroying a city?

Good news: This is probably not something you have to worry too much about during your lifetime. Maggie

What exploded over Russia? Space researchers explore, with infrasound sensors

The bizarre explosion in the skies over in Russia on Feb. 15, 2013 left scientists dumfounded. The asteroid 2012 DA14 was expected to pass some 17K miles over Indonesia, but the Russian impactor wasn't foreseen: it flew from the direction of the sun where telescopes couldn't see it, and surprised everyone hours before the more-publicized asteroid's flyby.

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).

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Another way to enjoy meteor showers: HAM radio

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.

Geminids Meteor shower: How to watch the big fireworks in the sky tonight

The Geminids Meteor shower is coming! Space reporter Miles O’Brien speaks with AtronomyNow.com’s night sky consultant, Mark Armstrong.

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Weird meteor shower to peak tomorrow night

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

Moon to screw up chances of Americans watching Perseid meteors

Bad news for U.S.-based astronomy buffs. You probably won't get a good look at the Perseid meteor shower happening Friday night. The Moon (you know, the Moon) will be getting all up in your business. Some particularly bright meteors might still be visible, however.

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?

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