Astronomie - Perseid Meteor Shower 2018: When, Where & How to See It This Month



According to NASA meteor expert Bill Cooke, the Perseids are perhaps the most popular meteor shower of the year; and in 2018, they'll be the best shower of the year. During the Perseids' peak this month, spectators should see about 60-70 meteors per hour, but in outburst years (such as in 2016) the rate can be between 150-200 meteors an hour. The meteor shower's peak will be visible both the nights of Aug. 11-12 and Aug. 12-13, Cooke said, but he's inclined this year to lean toward the night of Aug. 12-13 for the better show. (Both, however, should be spectacular.)


"This year the moon will be near new moon, it will be a crescent, which means it will set before the Perseid show gets underway after midnight," Cooke told "The moon is very favorable for the Perseids this year, and that'll make the Perseids probably the best shower of 2018 for people who want to go out and view it." The Perseids are rich in fireballs, so the show should be even better.

Skywatchers looking out for the Perseids should also be able to see Mars (visible until about 4 a.m. local time) and Saturn (visible until about 2 a.m. local time); Venus and Jupiter both set before the Perseids are best viewed (9:30 p.m. and 11 p.m., respectively).

Earth will pass through the path of Comet Swift-Tuttle from July 17 to Aug. 24, with the shower's peak — when Earth passes through the densest, dustiest area — occurring on Aug. 12. That means you'll see the most meteors in the shortest amount of time near that peak, but you can still catch some action from the famed meteor shower before or after that point.


The 2017 Perseid meteor shower peaked around 1 p.m. EDT (1700 GMT) on Aug. 12, so the nights of Aug. 11-12 and Aug. 12-13 saw the highest rates. The meteors appear to radiate out of the constellation Perseus, from which they take their name.

You can see the Perseid meteor shower best in the Northern Hemisphere and down to the mid-southern latitudes, and all you need to catch the show is darkness, somewhere comfortable to sit and a bit of patience.

Comet Swift-Tuttle is the largest object known to repeatedly pass by Earth; its nucleus is about 16 miles (26 kilometers) wide. It last passed nearby Earth during its orbit around the sun in 1992, and the next time will be in 2126. But it won't be forgotten in the meantime, because Earth passes through the dust and debris it leaves behind every year, creating the annual Perseid meteor shower.

When you sit back to watch a meteor shower, you're actually seeing the pieces of comet debris heat up as they enter the atmosphere and burn up in a bright burst of light, streaking a vivid path across the sky as they travel at 37 miles (59 km) per second. When they're in space, the pieces of debris are called "meteoroids," but when they reach Earth's atmosphere, they're designated as "meteors." If a piece makes it all the way down to Earth without burning up, it graduates to "meteorite." Most of the meteors in the Perseids are much too small for that; they're about the size of a grain of sand.

The key to seeing a meteor shower is "to take in as much sky as possible," Cooke said. Go to a dark area, in the suburbs or countryside, and prepare to sit outside for a few hours. It takes about 30 minutes for your eyes to adjust to the dark, and the longer you wait outside, the more you'll see. A rate of 60-70 meteors per hour, for instance, means around one meteor per minute, including faint streaks along with bright, fireball-generating ones.

Some skywatchers plan to camp out to see the Perseid meteor shower, but at the very least, viewers should bring something comfortable to sit on, some snacks and some bug spray. Then, just relax and look upward for the celestial show.




Update: 9.08.2018


Catch the Perseid Meteor Shower at Its Peak


“Stars fell like weaving in the south, unceasingly through the night.” So a city gazetteer printed in Shanxi, China, described the sky above Fenyang on August 10, 1862. Calculating backward, scholars have determined that the “weaving stars” witnessed by the townspeople were in fact Perseid meteors, falling at a time when the shower’s radiant, the point from which the meteors appear to emanate, lay low in the sky.

The Perseids are associated with the short-period Halley-type comet 109P/Swift-Tuttle, which was independently discovered by American astronomers Lewis Swift and Horace Tuttle as it approached perihelion in July 1862. When Earth crosses Swift-Tuttle’s orbit, bits of dust and rocks left behind by the comet hit the planet’s atmosphere, creating the light show we know as the Perseid meteor shower. In years when Swift-Tuttle reaches perihelion, the number of visible meteors significantly increases, which explains the dramatic display of August 1862. Since the comet has a 133-year orbital period and last visited the inner solar system in 1992, we’ve got another 107 years to go before that possibility arises again. Occasional bump-ups in the number of detected meteors do occur when Earth passes close to dust trails left behind during even earlier visits. However, the next such major outburst isn’t predicted until 2028. Even so, the “ordinary” Perseids make for a strong shower and an impressive spectacle. Under ideal, dark skies, viewers may see more than 50 meteors in an hour.

The extant Chinese records for the 1862 event all come from northern China, suggesting unfavorable weather in the south that year. Here and now in 2018, we hope for good weather for the summer’s greatest shower, because viewing conditions should otherwise be perfect. The shower’s predicted peak falls on the evening of August 12th, soon after new Moon (9:58 UT August 11th). Weather and light pollution (and possibly mosquitoes) should be the only impediments to a good show. The best viewing will certainly be early on the mornings of August 12th and 13th, but don’t wait for the predicted peak to go outside. Perseids begin streaking across the sky in mid-July, when the radiant is still in Cassiopeia, and the odd shower meteor will continue to be visible until around August 24th.

The easiest way to view a meteor shower is to kick back with a lawn chair and a sleeping bag. All you really need to do to see the show is look up, stay warm, and stay awake. Find the darkest sky you can, away from street lights. For most viewers in the Northern Hemisphere, shower meteors can appear any time after evening twilight ends, since the radiant in Perseus is circumpolar (i.e., up all night). So start looking as soon as evening twilight ends. These early evening space streaks will be long, showy “Earthgrazers” that skim Earth’s upper atmosphere. As the radiant moves higher in the northeast throughout the evening, the meteors will become more frequent and appear all over the sky. The later you observe, the more meteors you’ll see, and the best hours fall between midnight and dawn.

The most suitable equipment for watching a meteor shower are desire and dark skies, but if you’d like to document your observations more formally, the International Meteor Organization (IMO) recommends that visual observers track sky activity for at least 1 hour, with reports broken into short intervals of no longer than 15 minutes. For more detailed instructions regarding recording and reporting, visit the IMO Visual Observations page. Earth may encounter a Perseid filament — a relatively young accumulation of meteoroids — on August 12th around 20h UT. There’s also a possibility of our planet meeting an old Swift-Tuttle dust trail on August 13th around 1h 27m UT. Accurate observation records may help detect activity connected to filament and meteoroid clump.

Quelle: Sky&Telescope

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