Category: Meteor Showers

Would you like to see a piece of Halley’s Comet streak past a planet that looks like an exploding star? No problem. Just set your alarm.

It’s going to happen, in plain view–no telescope required, on Thursday morning, Oct. 21st.

Go outside before sunrise, around 5:30 a.m. is best, and look east. The brightest object in that direction is the planet Venus. It looks like a star going supernova. Above Venus lies Saturn, and below, near the horizon, is Jupiter. Every 10 minutes or so you’ll see a meteor streak among these planets. The meteors are pieces of Comet Halley.

“Every year around this time Earth glides through a cloud of dusty debris from Halley’s Comet,” explains Bill Cooke of the NASA Marshall Space Flight Center. “Bits of dust, most no larger than grains of sand, disintegrate in Earth’s atmosphere and become shooting stars.”

“It’s not an intense shower,” he says, “but it is a pretty one.”

Astronomers call it the “Orionid meteor shower,” because the meteors appear to stream out of a point (called “the radiant”) in the constellation Orion. The radiant is near Orion’s left shoulder. But don’t stare at that spot, advises Cooke. Meteors near the radiant seem short and stubby, a result of foreshortening. Instead, look toward any dark region of the sky about 90 degrees away. The vicinity of Venus or Jupiter is good. You’ll see just as many Orionids there, but they will seem longer and more dramatic.

Framing the scene are several bright stars: Sirius, Regulus, Procyon and others. Pay special attention to Castor and Pollux in Gemini. They’re arranged in an eye-catching line with Saturn.

To sum it up in one word: “sparkling.” Two more words: “early” and “cold.” Or how about “worth waking up for?” You decide.

More about the Orionids
The Orionids are related to the eta Aquarids, a southern hemisphere meteor shower in May. Both spring from Halley’s Comet.

Earth comes close to the orbit of Halley’s Comet twice a year, once in May and again in October,” explains Don Yeomans, manager of NASA’s Near-Earth Object Program at the Jet Propulsion Laboratory. Although the comet itself is rarely nearby–it’s near the orbit of Neptune now–Halley’s dusty debris constantly moves through the inner solar system and causes the two regular meteor showers.

In 1986, the last time Comet Halley swung past the Sun, solar heating evaporated about 6 meters of dust-laden ice from the comet’s nucleus. That’s typical, say researchers. The comet has been visiting the inner solar system every 76 years for millennia, shedding layers of dust each time.

At first, the bits of dust simply follow the comet, which means they can’t strike our planet. Earth’s orbit and Halley’s orbit, at their closest points, are separated by 22 million km (0.15 AU). Eventually, though, the dust spreads out and some of it migrates until it is on a collision course with Earth.

“Particles that leave the nucleus evolve away from the orbit of the comet for two main reasons,” explains Yeomans. “First, gravitational perturbations caused by encounters with planets are different [for the dust and for the comet]. Second, dust particles are affected by solar radiation pressure to a far greater extent than the comet itself.”

“The orbital evolution of Halley’s dust is a very complicated problem,” notes Cooke. No one knows exactly how long it takes for a dust-sized piece of Halley to move to an Earth-crossing orbit — perhaps centuries or even thousands of years. One thing is certain: “Orionid meteoroids are old.”

They’re also fast. “Orionid meteoroids strike Earth’s atmosphere traveling 66 km/s or 148,000 mph,” he continued. Only the November Leonids (72 km/s) are faster. Sometimes fast meteors explode, and they leave glowing “trains” (incandescent bits of debris in their wake) that last for several seconds to minutes. These trains, blown by upper atmospheric winds into twisted and convoluted shapes, can be even prettier than the meteors themselves.

You never know what you might see, before sunrise, on a magical Thursday morning.

Original Source: Science@NASA Story

The annual Perseid meteor shower will peak the night of August 11. Members of the news media are presented with an excellent opportunity to witness and photograph the event.

The best views of the meteor shower will be from dark, rural locations. The darker the observing site, the easier it will be to observe or photograph the meteors. Most of the best sites in Southern California are in the desert and mountain areas located east of the major cities.

Meteor photography should not begin until it is completely dark, after 9 p.m. Early in the evening meteors will appear in the northeastern part of the sky. As the night progresses, the meteors will be more numerous and can appear anywhere in the sky. Most of the meteor shower activity will take place after midnight, when observers may see them at the rate of about one per minute.

Meteors occur at random times and locations in the sky. The best technique for capturing them photographically involves using a standard 35-mm camera that has a “B” or bulb setting. The camera needs to be securely fastened to a tripod. A cable release will allow for control the exposures with a minimum of vibration. Film with a speed of ISO 400, 800, or 1000 is recommended. Avoid using a telescope or a telephoto lens,because they reveal only a tiny fraction of the sky, thus greatly reducing your chances of catching a meteor. On the other hand, wide-angle lenses are more likely to catch a meteor, although the meteor will appear small on the photographic image. A 50mm lens is probably a good compromise.

To photograph the meteors, pick an area of the sky, focus on infinity and start the exposure. Those shooting with film may wish to hold the exposure until a meteor is captured, end the exposure, and then start another. Any interesting foreground objects in the shot can be nicely “painted in” to the picture with a flashlight beam shining on them. Don’t be afraid to experiment.

Photographers shooting digitally have some advantages and disadvantages over those shooting with film. Digital photography provides the photographer with rapid feedback as to how the exposures are going. However, it should be noted that for most digital cameras, longer exposures mean more noise in the image. This can be defeated by either taking short exposures (less than a minute) or taking a dark frame of the same length as your exposures of the sky. This dark frame can later be subtracted with a program such as Photoshop.

For anyone attempting to capture the meteor shower on video, the International Meteor Organization recommends using a fast lens and a powerful image intensifier. Specific details are online at http://www.imo.net/video/

Cloud-free skies are essential to having the best view of the meteor shower. The National Weather Service often does not provide the kind of forecast necessary for astronomical observations. A good choice is to check out the Clear Sky Clock. A list of all of the Clear Sky Clock sites in California can be found online at

http://cleardarksky.com/csk/prov/California_clocks.html

An explanation of how to read the data is provided on the web page. Simply choose a site close to where you will observe the meteor shower. Should clouds intervene, it is important to remember that the shower lasts for several nights, giving you another opportunity.

Original Source: Caltech News Release

The Perseid meteor shower, an annual celestial event beloved by millions of skywatchers around the world, returns to the night sky this coming week.

Sky & Telescope magazine predicts that the Perseid shower will reach its peak late Wednesday night and early Thursday morning, August 11?12. The rate of activity should pick up steam after midnight until the first light of dawn. North America, especially the West and Hawaii, is optimally positioned to catch the best of the shower.

An observer under a dark sky might typically see more than 60 Perseids per hour between midnight and dawn. Since the waning crescent Moon will be only three days from new at the time of shower maximum, posing minimal interference with the view, this is an opportune year for watching them.

You’ll need no equipment but your eyes. The darker your sky, the better ? any artificial light pollution in your sky will reduce the number of meteors that are visible. But even if you live in an urban or suburban area, you have a good chance of seeing at least some meteors. Find a dark spot with a wide-open view of the sky. Bring a reclining lawn chair, insect repellent, and blankets or a sleeping bag; clear August nights can get surprisingly chilly.

“Go out after about 11 p.m. or so, lie back, and watch the stars,” says Sky & Telescope senior editor Alan MacRobert. “Relax, be patient, and let your eyes adapt to the dark. With a little luck you’ll see a ‘shooting star’ every couple of minutes on average.”

Perseids can appear anywhere and everywhere in the sky. So the best direction to watch is wherever your sky is darkest, probably straight up. Faint Perseids appear as tiny, quick streaks. Occasional brighter ones may sail across the heavens for several seconds and leave a brief train of glowing smoke.

If you trace each meteor’s direction of flight backward far enough across the sky, you’ll find that your imaginary line crosses a spot in the constellation Perseus, near Cassiopeia. This is the shower’s radiant, the perspective point from which all the Perseids would appear to come if you could see them approaching from interplanetary space. The radiant is low in the north-northeast before midnight and rises higher in the northeast during the early-morning hours.

Don’t give up if it’s cloudy Wednesday night. The Perseid shower lasts for about two weeks, with good rates in the predawn hours of August 10th through 15th. This year the ever-thinning Moon becomes less of a problem with each passing night. Far fewer meteors will appear before midnight, even on the night of the shower’s maximum, because the radiant is then quite low in the sky. The radiant is always low or below the horizon for Southern Hemisphere countries like Australia, New Zealand, and South Africa, where few, if any, Perseids can be seen.

The Perseid meteoroids are tiny, sand- to pea-size bits of rocky debris that were shed long ago by Comet Swift-Tuttle. This comet, like others, is slowly disintegrating as it orbits the Sun. Over the centuries, its crumbly remains have spread all along its 130-year orbit to form a sparse “river of rubble” hundreds of millions of miles long.

Earth’s own path around the Sun carries us through this stream of particles every mid-August. The particles, or meteoroids, are traveling 37 miles per second with respect to Earth at the place where we encounter them. So when one of them strikes the upper atmosphere (about 50 to 80 miles up), it creates a quick, white-hot streak of superheated air.

For several years in the early 1990s the Perseids performed spectacularly, flaring with outbursts of up to hundreds of meteors per hour. The particles responsible for these outbursts were probably shed during Comet Swift-Tuttle’s swing by the Sun in 1862.

Astronomers Esko Lyytinen of Finland and Tom Van Flandern of Washington, DC, have alerted skygazers to the possibility that this “extra” Perseid peak could make a comeback in 2004. They predict that this year, the rubble trail released in 1862 will pass just 200,000 kilometers (125,000 miles)) inside Earth’s orbit on August 11th, just as observing conditions become optimal for meteor watchers in Eastern Europe and eastern North Africa eastward to central Russia, India, and western China.

Will the Perseids “storm” in 2004? There’s only one way to find out: Get outside and watch the show!

More about the Perseid meteors ? and how to watch and photograph them ? appears in the August 2004 issue of Sky & Telescope magazine and online in the articles listed at the end of this press release.

Original Source: Sky and Telescope News Release

Image credit: ESA
The annual Perseid meteor shower is coming, and astronomers say it could be unusually good this year.

The shower begins gently in mid-July when Earth enters the edge of a cloud of debris from Comet Swift-Tuttle.

Dust-sized particles will hit our atmosphere and appear to streak across the night sky. At first there will be just a few meteors each night, but then the rate will build. The Perseids are visible between 23 July and 22 August but, by 12 August, at the peak of the shower, skywatchers can expect to see possibly 80-100 meteors per hour if skies are clear.

This is a good year for Perseids for two reasons. First, the Moon is new in mid-August, so moonlight will not spoil the show as much as it would have done last year, had the sky been clear! Second, in addition to the usual shower on 12 August, there might be an extra show of meteors late in the evening of 11 August caused by a ?filament? of dust drifting across Earth’s orbit for the first time.

This filament, like all the dust in the Perseid cloud, again comes from Comet Swift-Tuttle. The difference is, the filament is relatively young. It ?boiled? off the comet in 1862. Other dust in the cloud is older (perhaps thousands of years old), more dispersed, and responsible for the month-long shower that peaks on 12 August. The filament will eventually disperse, too, but for now it retains some of its original ribbon shape.

According to current predictions, Earth will move through the filament on Wednesday, 11 August at 23:00 CEST. This will produce a surge of mostly faint meteors over Europe and Asia. Because of the way Comet Swift-Tuttle?s orbit is tilted, its dust falls on Earth’s northern hemisphere. Meteors appear to stream out of the constellation Perseus, which is barely visible south of the equator.

Later that night and into the early morning hours of Thursday, 12 August, observers will see the ?traditional? Perseid peak caused by the older dust from Swift-Tuttle. The best time to look for these traditional Perseids is during the hours before dawn on Thursday.

How to observe the Perseids
The best way to observe them is to look towards the northeast after dark. They appear to originate from the constellation of Perseus which at midnight lies just below the easily recognisable ‘W’ of Cassiopeia.

Try looking around 22:00-23:00 CEST on Wednesday, when Perseus is hanging low in the eastern sky. You won’t see many meteors then, but the ones you do see could be memorable. On Thursday morning, the highest frequency of meteors is likely just before dawn.

Original Source: ESA News Release