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  • It's a hot night for cool meteors

    Jimmy Westlake / Colorado Mountain College

    A Geminid meteor streaks across the night sky, with circular star trails whirling the background, in a time-exposure photo made by astronomer Jimmy Westlake in December 1985.

    By Alan Boyle, Science Editor, NBC News

    December isn't exactly prime time for sitting out in the cold and dark, but tonight could be the exception: The most productive meteor shower of the year is due to reach its peak tonight. Don't just take it from me -- you can ask the experts yourself during a series of online chats building up to the Geminid meteor shower.

    There's lots that's appealing about this year's Geminids: Astronomers say the shooting stars could be spotted at a rate of more than one per minute under peak conditions (the equivalent of 60 to 120 per hour). The moon is in its first-quarter phase, meaning that it'll be setting around midnight and won't be glaring in the sky during the peak viewing hours (midnight to morning twilight). Earth is projected to pass through the thickest part of the meteor debris stream during the wee hours of the morning for North Americans, who are in just about the best position to see the maximum flash.

    So what's the problem? Why aren't the Geminids as highly anticipated and well-known as the Perseids of August or the Leonids of November. Well, the biggest drawback is that it's c-c-c-cold out there this time of year. That means it's more important than ever to bundle up, have a comfortable lounge chair and sleeping bag at the ready, and bring along hot beverages to keep warm.

    This chart indicates the radiant for the Geminids -- the point in the sky from which the meteors appear to emanate.

    The best viewing is available far from the glare of city lights, where you have an unobstructed view of as much of the sky as possible. Geminid meteors are so named because they appear to emanate from a point in the constellation Gemini. But the shooting stars can appear anywhere in the sky, so don't just stare at Gemini. There's no need to gaze through binoculars, though you may want to take them along to see other celestial points of interest.

    The early reviews are already streaming in, and it's a strong thumbs-up: Peak rates rose to as high as 40 meteors per hour last night, according to statistics gathered by the International Meteor Organization.

    Exactly when and where should you go skywatching tonight? And what will you see? Three online tools can help you sort out those key questions:

    • When? NASA's Fluxtimator is a Java-based online application that lets you specify your location, date, viewing conditions and the meteor shower you're interested in -- and then shows you how many meteors you could expect to see. Today, it's telling me that I might spot 80 meteors per hour at 1 a.m. PT if I'm in the countryside around the Seattle area. That's assuming that the skies are clear.
    • Where? The Clear Sky Chart is a fantastic database that gathers up weather data for skywatching hot spots in the United States, Canada and parts of Mexico, and translates all those readings into graphical charts showing you what to expect at a particular location, hour by hour. You can get a quick read on whether it's likely to be cloudy or clear, what the atmospheric "seeing" conditions will be, and when dawn is due to start breaking. I can see already that the forecast is not that great for my favorite viewing spot, Rattlesnake Lake in the Cascade foothills.
    • What's it all about? NASA's Marshall Space Flight Center has set up an online chat about the Geminids with meteor experts Danielle Moser and Rhiannon Blaauw. They can provide a preview of the event, advice for skywatching, and the science behind the meteor phenomenon. The main event starts at 11 p.m. ET, when NASA astronomer Bill Cooke presides over a late-night meteor chat. That's due to last until 5 a.m. ET.

    One of the big mysteries surrounding the Geminids has to do with their origin. Annual meteor showers like the Perseids and Leonids are generally fueled by the gritty debris left behind by a comet that just happened to cross Earth's orbit. When those bits of rock hit the upper atmosphere at a speed of 22 miles per second, air friction causes them to vaporize -- leaving behind the glowing streaks we associate with shooting stars.

    The weird thing about the Geminids is that it's thought to be caused by debris from an orbit-crossing asteroid rather than a comet. The asteroid Phaeton, to be precise. Astronomers have come around to the view that Phaeton may have started out as a classic comet but eventually lost its ice, leaving the rocky core we see today. The leading hypothesis is that Phaeton's rock becomes fractured due to thermal stresses when it passes close to the sun, and leaves behind fresh trails of debris during each orbit. But there are some things about that hypothesis that don't quite add up.

    "The Geminids are my favorite, because they defy explanation," Cooke observed in a NASA preview that explains the mystery more fully.

    For general advice about maximizing your viewing experience, review my top 10 meteor-watching tips from August. And if you miss tonight's show due to weather or holiday-season weariness, never fear: The Geminids are expected to provide encore performances through the next few nights. Then it'll be only a few more days until the next celestial extravaganza: the total lunar eclipse on Dec. 20-21.

    Update for 1:10 p.m. ET: The MeteorWatch.org website is keeping track of meteor sightings around the world. To share your shooting-star reports via Twitter, just include the term #meteorwatch and your location in your tweet. That way they'll show up on this Meteor Map.

    Update for 3 p.m. ET: NASA is using a Java-based client for the Geminids chat, so you'll have to have Java enabled in order to participate. The chatsters are getting lots of great questions, and I expect it will be the same tonight when Cooke is on the show. Starting this afternoon, you should be able to watch live video from Marshall Space Flight Center's "meteor-cam," via the same Web page used for the chat.

    Got a celestial sighting to report? Share your skywatching experiences as a comment below. You can also connect with the Cosmic Log community by "liking" the log's Facebook page or following @b0yle on Twitter. 

  • Another news flash from Jupiter

    A Japanese amateur astronomer witnessed a flash on Jupiter over the weekend - less than three months after similar blip, apparently caused by a meteor fall, created a sensation among astronomers. The event suggests that the giant planet may be experiencing shooting stars more frequently than scientists thought, and that it's just a case of looking in the right place at the right time.

    That's what Masayuki Tashikawa was doing early Saturday morning Japan time (around 18:22 GMT or 2:22 p.m. ET Friday), when he had his video-equipped telescope pointed in Jupiter's direction from Kumamoto city on the island of Kyushu. In the 4-second video clip above, the second-long flash can be seen toward the lower left, about halfway through the clip.

    "I took it for noise signals at first, but I was really surprised because the image of the light remained on the video," Tashikawa told Kyodo News.

    The phenomenon looks like a repeat of the flash spotted by longtime Jupiter-watchers Anthony Wesley and Christopher Go on June 3. Their observations, combined with follow-up looks by the Hubble Space Telescope, led astronomers to conclude that the flash was caused not by an exploding asteroid or comet, but instead by a fiery meteor that didn't leave a lasting mark on Jupiter's cloud tops.

    Junichi Watanabe of the National Astronomical Observatory of Japan notes the similarity in a blog post reporting the latest flash.

    In the days ahead, professional as well as amateur astronomers will be looking for any traces left behind by this weekend's event. The preliminary verdict is that there's no visible scar - which would distinguish both of this year's observed flashes from the "Great Black Spot" impact of July 2009.

    Amateur astronomers have already revolutionized the search for asteroids, and now it looks as if they're doing the same thing for the systematic monitoring of Jupiter's cloud tops. Sky & Telescope's Kelly Beatty quotes Glenn Orton, an astronomer at NASA's Jet Propulsion Laboratory, as saying it may be time "to establish a worldwide network of Jupiter-monitoring telescopes so that the planet can be watched 24/7."

    Beatty also points out that more observations would be useful to confirm that the flash truly came from Jupiter and not from the random glint of an Earth-orbiting satellite. Let's hope this latest news flash will spark confirmation of this weekend's event - and future flashy finds.

    Update for 1:10 a.m. ET Aug.. 23: SpaceWeather.com passes along a confirmatory series of pictures from another Japanese amateur astronomer, Aoki Kazuo of Tokyo. The 500-mile (800-kilometer) separation of the two observers "rules out an event near Earth and reinforces the association of the flash with Jupiter," SpaceWeather.com's Tony Phillips writes.

    For more on the flash:

    Join the Cosmic Log corps by signing up as my Facebook friend or hooking up on Twitter with @b0yle. And if you really want to be friendly, ask me about "The Case for Pluto."

  • See a meteor shower in a minute

    Meteor showers are marvelous sights, as myriads of stargazers found out a week ago. But seeing them can sometimes be inconvenient. To get the best view, you have to go far from city lights and stay up until the wee hours of the morning. The ideal situation would be to camp out in a beautiful location like California's Joshua Tree National Park and keep your eyes open all night.

    That's exactly what photographer Henry Jun Wah Lee did last week. He set up his camera in the park for two nights around the peak of the Perseid meteor shower (Aug. 12 and 15), took a series of exposures, and spliced them together artfully into a multi-day time-lapse sequence.

    The result makes it seem as if the meteors are popping like fireworks amid the multitudes of stars in the Milky Way ... two nights' worth in just a little more than minute. But not all of the flashes you see are shooting stars.

    "I did catch some airplanes," Lee told me today. The streaks that appear to move across the sky are more likely nighttime airplane transits rather than meteors. But there's a killer meteor flash that pops up around the 30-second mark, leaving a little wisp of vapor in its wake.

    "When that happened, it lit up the whole sky like a flash of lightning," Lee said.

    For still more August awesomeness, check out the Perseid meteor gallery at SpaceWeather.com.

    The Perseid show is pretty much over, as this activity graph from the International Meteor Organization illustrates. But there's more to come: The highlights ahead include the Leonids of Nov. 17 and the Geminids of Dec. 13-14. That timetable should give you enough advance warning to scope out a picturesque viewpoint ... at Joshua Tree or closer to home.

    The video above is by Henry Jun Wah Lee via Vimeo. Tip o' the Log to Bad Astronomy.

  • See (and hear) the meteor show

    Dennis di Cicco / Sky & Telescope

    A bright Perseid meteor streaks over buildings at the Stellafane amateur astronomy convention in Springfield, Vt., on Aug. 7.

    When the late show is over, turn off the TV, step outside and catch a late, late show in the night sky. It's prime time for the Perseids, arguably the most accessible meteor shower of the year.

    "If you want comfort, this is the shower to see," said Bill Cooke, the head of NASA's Meteoroid Environment Office at Marshall Space Flight Center in Alabama.

    Every night, Cooke has been turning on a couple of all-sky cameras in Alabama and Georgia to catch meteor trails as they streak through the sky. This year's been a great one for the Perseids, in large part because the moon doesn't glare in the sky when the show is getting good.

    The absolute best viewing is expected Thursday night - actually, between midnight Thursday and dawn on Friday. Perseid meteors should be visible every night from now until next week. At its peak, observers could see at least one meteor every minute, Cooke told me. You just have to know where and when to look - and the experience goes much more smoothly if you make a few preparations.

    First, some basic facts about meteors: As explained in our interactive graphic, meteor showers occur when our planet plows through a trail of space grit left behind by a comet. Those bits of grit zip through the upper atmosphere at speeds of more than 125,000 miles per hour, lighting up a trail of ionized air.

    Don't worry: There's virtually no risk of being hit by one of these falling stars. Most of this grit burns up dozens of miles above us. A week ago, Cooke's camera in Alabama snapped a picture of a fireball lighting up the sky much more brightly than any planet - and even that sparkler self-destructed at an altitude of about 56 miles.

    Perseid

    NASA

    An all-sky camera captures a fireball streaking over Alabama on Aug. 3 during the Perseid meteor shower.

    The Perseids are produced by trails of grit left behind by Comet Swift-Tuttle during its 133-year orbit. Earth starts plowing through the Swift-Tuttle debris in late July, and the height of the shower comes annually around Aug. 12-13. The Perseids are so named because they appear to emanate from a point in the constellation Perseus, also known as a "radiant." Because the radiant is in northern skies, Northern Hemisphere observers are in a more favorable position to see the shower.

    The strength of the shower varies from year to year, depending on what part of Swift-Tuttle's debris trail our planet moves through. Based on what he's seen so far, Cooke expects a "very good Perseid shower this year."

    The good news is that Cooke is making himself available on Thursday to discuss the shower via this NASA chat page. He'll be taking questions during the afternoon, starting at 3 p.m. ET, and then he'll be back online from 11 p.m. ET to 5 a.m. ET Friday. The bad news is that all this Internet chatting will seriously cut into his own meteor-watching time.

    "I'll be in the press room with no view of the sky," he said.

    Perseid radiant

    NASA

    Perseid meteors appear to emanate from a point in the constellation Perseus, as shown in this graphic depicting the northeastern sky at around midnight. Although the meteors can appear in any part of the sky, their tails can be traced back to that point..

    A couple of years ago, I put together a top-ten list of tips for maximizing your meteor-watching experience. Here's an updated game plan for making the most of the meteors, assembled with Cooke's help:

    1. Pick a viewing spot far away from city lights, where the skies are likely to be clear and wide-open. Higher elevations are usually better than lower elevations, and you don't want to be surrounded by trees, buildings or other obstacles to viewing.
    2. For help in site selection, you can check out the Clear Sky Chart website, which provides weather conditions for skywatching ... and links to popular viewing locations on a state-by-state basis. Your local astronomy club can also point you in the right direction. This year, some events for amateur astronomers are timed to take advantage of the Perseids - for example, star parties in California's Mojave Desert, in Michigan, in Oregon and Washington state.
    3. Bring a blanket or a chaise lounge to lie back on. Have layers of clothing available in case the air turns chilly at night. Bring snacks or drinks. Bring a flashlight so you can find your way through the dark. Bring a music player or radio if you need a diversion. And bring your friends. Meteor-watching sets a great mood for chatting about cosmic issues, or meditating on the wonders of the heavens.
    4. Don't give up too quickly. Give your eyes plenty of time to get accustomed to the dark. Although the meteors appear to emanate from the radiant in Perseus, don't focus exclusively on that point. "The closer the meteor is to the radiant, the shorter the trail is," Cooke explained. "I always tell people to look straight up, because that way, they'll catch plenty of meteors far enough from the radiant to see a trail."
    5. The later you can stay up, the better. "It's a late-night shower," Cooke said. You could start seeing Perseids at around 9:30 p.m., and those "Earth-grazers" tend to leave the longest, most impressive trails. But the show doesn't get good until after midnight, and the peak usually comes just before morning twilight begins.
    6. To get a better sense of what to expect at which time, use NASA's Fluxtimator. When you click in the right coordinates for meteor shower, date, location and viewing conditions, the Java-based calculator charts what the estimated meteor flux will be at different times.
    7. If you're totally clouded out, you can try listening to the meteors. NASA's Perseid Web page includes a video feed that shows what Cooke's cameras are seeing, accompanied by a soundtrack of radio blips created by the meteor streaks. Cooke said it's also possible to hear the radio blips by tuning your FM radio to a station so distant that all you can hear is the hiss of a carrier wave. "When a meteor passes, you'll hear a blip kind of like a sonar blip," Cooke said. Here's a spooky audio file that gives you an idea what the radio echoes sound like. SpaceWeather Radio also lets you hear the meteors, and you can always check out the Perseid Fireball Cam.
    8. The meteors aren't the only game in town: Saturn, Mars and Venus form a striking planetary triangle in western skies just after sunset, and the International Space Station is visible from many North American locations just before sunrise. Impress your friends by telling them that the bright star near the zenith at around 11 p.m. is Vega (made famous by the "Contact" movie). and that the bright "star" in the southeast is the planet Jupiter. If you're far enough north (or south), you might even see an aurora.
    9. If you want to share your meteor sightings with the world via Twitter - and find out where the sightings are sizzling - the MeteorWatch website is the place for you.
    10. Even if you miss the meteor shower completely, you can click through SpaceWeather.com's meteor gallery and catch up on the highlights. And you can start making plans for the Leonid meteor shower (peaking Nov. 17-18, unfortunately during a nearly full moon) as well as the Geminid meteor shower (peaking Dec. 13-14).

    Cooke noted that December's Geminids are the equal of August's Perseids, based on the number of meteors you should be able to see. "But nobody likes to freeze their backside," he added. Which gets back to the comfort angle.

    Whatever you do, don't obsess over how many meteors you're seeing (or not seeing) per hour. The Perseids are a good excuse to get outside in the summer, experience nature's wonders and then share those experiences. Last night, for example, I saw exactly one meteor from my viewing spot, a half-hour's drive outside Seattle. One meteor! But I also saw mountain vistas, a deer with magnificent antlers lurking by the side of a forest road, and the Milky Way in all its glory. Even setting aside the meteor, it was well worth the trip.

    That's my experience. What's yours? Feel free to share your stories of skywatching adventures past and present in the comment space below.

    More Perseid guides on the Web:

    For more about the Perseids, check out this posting from last week. If you have some Perseid pictures that you're proud of, share them using our FirstPerson photo in-box. Join the Cosmic Log corps by signing up as my Facebook friend or hooking up on Twitter with @b0yle. And if you really want to be friendly, ask me about "The Case for Pluto."

  • Get the most out of the meteor show

    Doug Murray / Reuters file

    A Perseid meteor streaks toward the horizon in Palm Beach Gardens, Fla., on Aug. 12, 2008. August's annual meteor shower is shaping up as a particularly good show this year.

    This year's Perseid meteor shower is shaping up as a beaut. Thursday is the big night - not only to see shooting stars, but to see the planets as well.

    The Perseids are among the year's best-known meteor showers, especially for mid-northern latitudes. Here's why: The show begins ramping up in late July and hits its peak around Aug. 12-13, when it's usually pleasant to hang around outdoors in the northern hemisphere. Perseid meteors appear to radiate from the constellation Perseus, which is high up in the sky at about 3:30 a.m. in northern latitudes - prime time for meteor watching.

    But the big attraction comes down to how many shooting stars you can see: During this time of year, Earth plows through the trails of space grit that have been laid down by Comet Swift-Tuttle as it makes its 130-year orbit around the sun. When those particles of grit zip through the upper atmosphere, they heat up to incandescence and create those bright streaks we all know and love.

    Fortunately for meteor-watchers, there's a lot of grit out there.

    "The whole shower, we think, is about 160,000 years old," Peter Jenniskens, a meteor astronomer at the California-based SETI Institute, told me. "The bulk of the shower you see is 5,000 years old."

    Skywatchers have tracked the Perseids for centuries. In some circles, the meteors are known as "the Tears of St. Lawrence," because the show reaches its peak around Aug. 10 - the feast day of St. Lawrence, a third-century Christian martyr. It wasn't until 1867 that scientists figured out that a comet was behind the meteoric display.

    The sky conditions are nearly ideal for this year's show, because the moon is just a few days past its new phase. When the moon is full, its glare overwhelms the meteor flashes in the night sky, making viewing problematic. But this year's crescent moon will be far below the horizon by midnight, when the meteor show enters prime time.

    You'll be good to go as long as you can get away from cloudy skies and the glare of city lights. Find an open area that gives you as wide a view of the sky as possible. Lie back on a blanket or chaise lounge, and give your eyes time to get accustomed to the darkness. You might want to bring along something warm to drink, to help you stay awake. It's a lot more fun if you go out with a group. If you're on your own, you can plug in to some tunes or an audiobook as you gaze into the night. But you may want to take in the silence instead: Some people swear they can hear the sounds of meteors zooming past.

    Perseid radiant

    NASA

    Perseid meteors appear to emanate from a point in the constellation Perseus, as shown in this graphic depicting the northeastern sky at around midnight. Although the meteors can appear in any part of the sky, their tails can be traced back to that point..

    If viewing conditions are absolutely perfect, you could see a meteor every minute at the height of the shower, which generally comes around 3:30 to 5:30 a.m., depending on your latitude. Is that past your bedtime? Don't sweat it; there's actually a lot to be said for watching the skies in the evening. During that time frame, the Perseid meteors streak at a narrow angle through the atmosphere. "You don't get as many meteors, but you get these long streaks - very nice!" Jenniskens said.

    Planetary triangle

    Starry Night Software via Space.com

    A planetary triangle in western skies after sunset..

    This year, early evening is also prime time for seeing a pretty grouping of planets: Venus, Mars and Saturn can be identified as the sparkling points of a triangle in western skies between sunset and about 10 p.m. local time. Around midnight, bright Jupiter rises in the east and starts making its way toward the zenith. And in the wee hours of the morning, North Americans can spot the International Space Station's stately procession across the sky. (Check out Heavens-Above for planetary positions and NASA's satellite sighting website for the space station's schedule.)

    Jenniskens said Earth is due to pass directly through a grit trail that was laid down by Swift-Tuttle in the year 1479, at 16:49 GMT on Thursday. That timing doesn't do North American observers any good, because it's daylight at that time. But it does mean observers in, say, Hawaii or Japan could see twice as many meteors as they would under normal conditions. And the meteor rate should still be pretty good hours later when it's North America's turn to see the show.

    If Thursday night doesn't work for you, that's OK. The Perseids are known for having a gradual ramp-up and fade-out, so there's the potential for seeing a good show anytime through, say, Aug. 20. Way back on Aug. 10, NASA's Marshall Space Flight Center reported that a dramatic Perseid fireball, six times as bright as Venus, was sighted over Arkansas.

    "It's a very good start to this year's Perseid meteor shower," NASA's Janet Anderson writes. Amen to that!

    Here are additional online resources that help you make the most of this prime skywatching season:

    Update for 8:46 p.m. ET Aug. 11: Now that we're into the Perseids' peak viewing time, here's a fresher guide to the meteor shower.

    Feel free to add your meteor sighting reports as comments below. Join the Cosmic Log corps by signing up as my Facebook friend or hooking up on Twitter. And if you really want to be friendly, ask me about "The Case for Pluto."

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