Tonight is one of the odder meteor showers of the years. Why is it odd? Well for one, it’s called the Quadrantids — named after a constellation that got redefined years ago and no longer exists. For another, the parent object of the shower isn’t a comet, it’s an asteroid that used to be a comet. And third, the shower peaks very sharply, coming and going in only an hour or two!

Here’s the deal.

First, meteor showers occur when the Earth plows through a trail of debris in space, usually left by a comet orbiting the Sun. The meteoroids — the solid bits of material — are usually very small, no bigger than a grain of sand. As they plow through our atmosphere at speeds of dozens of kilometers per second, they burn up, turning into meteors (if they hit the ground they’re called meteorites, which is very rare). Normally, you can see several random meteors every hour on a dark night, but during showers there may be dozens.

The length of time a shower lasts depends on how wide the debris field is. For most meteor showers it’s millions of kilometers wide, and so the showers can take days to play out. But the stream for the Quadrantids is very narrow, and the shower lasts for only an hour or so! It peaks tonight around 2 – 3 a.m. Eastern US time (07:00 – 07:00 GMT). That’s not an exact period, so if you want to see them you should go out an hour or so before then. There may be as many as 100 meteors per hour during that time!

Unfortunately, the waxing gibbous Moon is up tonight, so it’ll wash out a lot of the shooting stars. People on the east coast of the US have the best shot, since the Moon will hopefully have set by the time the shower peaks. However, Central time zone folks have a good view too since the Moon will be low to the horizon. I’ll give it a try tonight, since it peaks at midnight my time (in Boulder) and that’s early enough even for me to stay up.

How do you watch? All you need is an open sky and a place to lie down and relax. Someplace dark, away from trees and buildings is best. Meteors zip across the sky, so the more sky you see the better. I have a page with general advice on how to watch meteor showers that’ll help. It was written for a different shower, but the advice still applies.

As I said, meteor showers come from debris shed by comets as they orbit the Sun. These bits of stuff more or less follow the same orbit as their parent comet, and we get showers when the Earth rams through this material. However, the Quadrantids come from an object called 2003 EH1, which looks more like an asteroid — comets usually have lots of ice, but this object doesn’t. However, it’s on a comet-like orbit, so it most likely used to be a comet long ago which lost all its ice, leaving just rocky material behind.

And finally, the name: meteor showers appear to radiate from one point in the sky, in much the same way all the lights in a tunnel seem to be coming from ahead of you as you drive through that tunnel. Showers are named after the constellation where the meteors appear to come from: the Perseids for Perseus, the Orionids for Orion, and so on. Constellations are arbitrary boundaries in the sky, like state or county lines. Quadrans Muralis was a constellation defined back in the 19th century, and still existed when the Quadrantids were named, but was divided up when the modern official lines were drawn in 1930. That part of the sky is near the tail of the Big Dipper; so the meteors will appear to radiate away from the north across the sky.

So again, what to do: find a dark, open site. Try to bring a chaise longue or something where you can lie back and see lots of sky. Looking straight up is best. You don’t need binoculars or a telescope or anything like that: just your eyes, and a sense of wonder. Meteor showers can be a lot of fun, so I hope you see some good ones tonight!

Image credit: Randy Halverson. That’s not a meteor from the Quadrantids, but it’s still pretty.

A few days ago, three astronomers from Mexico posted a paper online (PDF) claiming that an observation from 1883 indicates a small comet passed within a few thousand kilometers of the Earth’s surface, and perhaps as close as 500km! Had this hit us, we would’ve been hammered by thousands of explosions as powerful as the largest nuclear explosions ever detonated.

The thing is, I’m not buying it. While superficially the interpretation fits the observations, there are way too many problems with it.

Here’s the deal. During the days of August 12 – 13, 1883, a Mexican astronomer named Jose A. y Bonilla reported seeing hundreds of objects passing directly in front of the Sun. They were small, appeared fuzzy, and left behind a misty appearance. In total, Bonilla says he saw 447 such objects!

The authors of this new work claim that what Bonilla may have seen was the remnants of a small comet that had previously fragmented. We’ve seen comets do this, and in fact it’s somewhat common. In 2006, Hubble took the picture shown above of the comet 73P/Schwassmann-Wachmann 3, which had recently disintegrated. So that part isn’t too far-fetched. However, once you make that assumption, things get pretty dicey.

The authors use the observations by Bonilla to estimate the distance and size of the comet fragments. Bonilla observed these objects at an observatory in Zacatecas, Mexico, but they were not seen transiting the Sun by any other observatories anywhere else. This can be used to narrow down their location; it means they must have been close to Earth. Had they been far away then other observatories would have seen them moving across the Sun. It’s like a bird flying by just outside your window; someone looking out a different window wouldn’t have seen it, but a bird a few hundred meters away would be visible to both.

Doing some simple math, the authors calculate the comet fragments were no closer than about 500 km (300 miles) from the Earth’s surface, and no farther than about 65,000 km (40,000 miles).

This right there is enough for me to be extremely skeptical of this idea. When a comet breaks up, it spreads out. Even when intact, the material surrounding a comet can be tens or even hundreds of thousands of kilometers across! Claiming that a comet broke apart, yet managed to constrain its pieces to volume of space less than a few thousand kilometers across strains credulity.

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The annual Geminids meteor shower peaks tonight, so if you’re willing to brave the cold weather (assuming it’s cold where you are) then tonight is your best chance! I wrote a guide to watching meteors showers a while back (it’s for a different shower, but the general advice still holds true) that should help, too. I’ve heard rumors that things will be pretty good tonight for people on the east coast of the U.S. after midnight. If the clouds dissipate tonight I may go for them myself… now that it’s finally warmed up to the better side of the freezing point of water around here.

And if you do observe, you can join people across the planet and record your observations on Twitter using the hashtag #MeteorWatch. Universe Today has details.

The annual Leonid meteor shower peaks this year on or around Tuesday night. It’s a slow-peaking shower, so even if you go out tonight, or later than Tuesday, you’ll probably see a few meteors streaking across the sky.

I’ve written about them many times in the past; a review is on my Bad Astronomy site, and I wrote a guide to watching the Perseids which is still apropos of the Leonids. NASA’s science news page has lots of info, and the International Meteor Organization has technical aspects, too.

Leonids over Uluru image courtesy Vic and Jen Winter at ICSTARS.