16 November 2009

17 & 18 Nov: Leonids meteor showers

"Bright meteors - some with very bright red heads and greenish trails - could be seen streaking across the suddenly starry sky" is the description of a previous sighting. Among the best places for good sightings are on our shores where it is dark, away from light pollution and provides a clear view of the sky.
Photo from Tabwin.

Astronomers predict this year will be the most dramatic Leonids meteor shower as the earth passes close to the centre of the comet’s debris trail. And a special Leonids meteor shower gazing event has been organised at the Japanese Gardens this week. The best time to watch in Singapore is from 2 -3am until dawn.

Was it a Leonid let down? Here's some updates on the event.

More about the upcoming event
at the Japanese Gardens 17 and 18 Nov (Tue & Wed)

Astronomers have predicted that the annual Leonids might put up the most dramatic light show not seen in recent years as the earth passes close to the centre of the comet’s debris trail laid down in 1466. The ideal locations for viewing are in Asia and North America.

On stage, there will be performances by Kenji Williams, an audio visual art performer, while offstage, visitors will be entertained by the Science Buskers. For astronomy buffs, an accompanying meteorite exhibition, a talk by TASOS, on-site telescope viewing of the planet Jupiter and inflatable planetarium tours for children will also be held.

More details on astronomy.sg

Time: 8pm – 5am
(8pm–2am: activities/2am – 5am: free & easy)
Venue: Japanese Gardens
Website and contact: http://astronomy.sg/

What can we expect to see during a Leonids meteor shower?
Where else can we observe the showers? From the Singapore Science Centre website:
For more than a century, the Leonid meteor shower in November has been an annual observing ritual for skywatchers.

In Singapore, the Leonid meteor shower had received much publicity in 1998. From the late evening of 17 Nov (Tuesday) to the early morning of 18 Nov (Wednesday) 1998, a 35,000-strong crowd streamed into Sentosa to watch the Leonid meteor shower. Families, students and groups of teenagers pack Tanjong Beach, which is on the eastern tip of Sentosa Island. This was an ideal location because it was not much affected by sky-glow from the city lights.

There were also people watching at East Coast, Changi and some polytechnics. It did not rain fire, but in a short spell when clouds dispersed in the wee hours of the morning, meteors and fireballs raced across the heavens, to the applause and cheers of an expectant audience. At about 2.30 am of 18 November, the clouds lifted for an hour and about a dozen bright meteors - some with very bright red heads and greenish trails - could be seen streaking across the suddenly starry sky. But after that, the entire sky was once again shrouded in cloud.

In the year 1999, from the late evening of 17 Nov to the early morning of 18 Nov, the weather was miserable, with intermittent drizzle throughout the night. For the year 2000, the Leonid meteor shower in Singapore was not impressive. Some scientists predict that Earth is likely on a collision course with several more storm-producing dust trails both 2001 and 2002. However, predictions of meteor storms are notoriously unreliable. No one really knows how to do it properly. It is always risky to give any definite predictions. But be sure, as one of the veteran observers said, "If the peak arrives, it will be an experience for your lifetime."

The point from where the Leonid meteors appear to radiate is located within the constellation Leo and is referred to as the radiant. The radiant is located in the western portion of that constellation in what is commonly referred as the "sickle" or "backward question mark." It is at right ascension 10h 14m, declination +22 degrees. The radiant rises around 1:30 a.m. in Singapore from the eastern horizon during mid-November. Although a few Leonids may be observed prior to this, more will be seen after it rises. At about 3:30 a.m. the radiant is about 30 degrees above the horizon. Most meteor showers are active between midnight and dawn. The sightings of meteors increases toward the morning hours because it is after midnight that an observer's location is aimed in the direction of the Earth's path about the Sun. No matter how the shower performs, the best time to watch is from 2 or 3 a.m. in Singapore until the first light of dawn.

The radiant is not necessarily where to watch, however. The best direction to watch is simply the darkest part of the sky, perhaps 45 to 60 degrees from the radiant if you have a choice. The important thing about the radiant is its height above the horizon. The higher the radiant, the more meteors will appear all over the sky. Meteors would streak across a good portion of the night sky. Naked eyes are the best equipment we could use for meteor shower. The field of view of telescope is very small. It is not appropriate to use telescope for meteor shower observation.

Because the light of most meteors is faint, meteor observations should be made under conditions as dark as possible, away from city lights. When watching even the best annual showers, however, you need to be patient. You might see one meteor every minute or two on average. And that is under ideal, dark-sky conditions with no moonlight or artificial light pollution. Any skyglow dramatically cuts down the number you will see.

In view of the points mentioned above, Science Centre grounds may not be good enough as an observing site for the meteor shower. For your CC youth group, you are encouraged to look for a good observing site away from all city lights. You need dark clear skies to see the meteors. Everyone is hoping for good weather and clear skies, but November is usually a wet month. It is therefore advisable to bring along raincoat or umbrella when you are far away from any shelter. If you are caught in a storm, take precautions against strike of lightning in the open field.

Meteor shower this week as we cut through comet trails
Rachel Courtland, New Scientist 15 Nov 09;
Well-placed skywatchers could see hundreds of meteors an hour on Tuesday, at the peak of the annual Leonid meteor shower.

Meteors are bits of dust or rock that collide with Earth's atmosphere. The friction heats up gas particles that produce a glowing trail. A handful of meteors can be seen each hour on any clear night, but this number can spike significantly during a meteor shower.

The Leonid shower occurs each year when the Earth passes through streams of debris ejected by the comet 55P/Tempel-Tuttle, which often leaves behind dusty trails as it passes through the inner solar system every 33 years.

Earth will cut across the first such stream around 0900 GMT on 17 November, an event that is expected to produce dozens of meteors an hour. But the spectacle will reach its peak between 2100 and 2200 GMT, as Earth passes through two debris trails left by Tempel-Tuttle in 1466 and 1533.
Leonids rising

These stream crossings could create as many as 300 Leonid meteors per hour, according to NASA's Meteoroid Environment Office. Skywatchers in Asia and the easternmost parts of Europe will have the best view of these intense showers, because the sky will be dark and the apparent point of origin of the meteors – called the radiant – will be over the horizon.

The Leonid shower is so called because the radiant is in the northern constellation Leo. The best time to view the shower is after this spot rises, around 2400 GMT.

North American observers may be able catch a glimpse of dozens of meteors before dawn on 17 November, but an elevated number of meteors may also be visible on the following night. European observers will get their best glimpse of the shower after the peak, in the early hours of 18 November.

Leonid Meteor Shower: Best Sky Show Tonight
Andrew Fazekas, National Geographic News 16 Nov 09;
During the 2009 Leonid meteor shower, you may see anywhere from 30 to 300 shooting stars an hour, depending on whether you're in the right place to see tonight's showy peak, experts predict.

With the highest number of meteors streaking across the skies around 4:45 p.m. ET on November 17, the full Leonids peak will be effectively invisible for viewers in North America and Europe.

In those regions, sky-watchers are advised to venture out away from bright city lights between 2 a.m. and 4 a.m. on the 17th, when they should see 30 to 50 meteors an hour.

But in Asia, the peak happens during predawn hours, so observers there will have a front row seat for this year's display.

"Thanks to advances in computer power, since the 1990's we have been able to predict these upswings in activity," said William Cooke, head of NASA's Meteoroid Environment Office.

"This year there is going to be a Leonid strong outburst [during the peak], where the rates may race up to 300 per hour," Cooke said.

"But it may have a surprise in store, as well, and bring an unpredicted short peak at some point, so it's worth it for everyone [all around the world] to go out and look."

Leonids Shower a Temperamental Rock Star

The Leonids are so named because they seem to radiate from the constellation Leo, the lion, which rises above the northeastern horizon between 1 a.m. and 3 a.m., depending on your location.

Like other meteor showers, such as the Perseids and the Orionids, the Leonids happen when Earth plows through a trail of debris left in the wake of a comet orbiting the sun.

When a comet gets close to the sun, melting ice releases pieces of dust, most no larger than grains of sand. Earth annually crosses paths with the orbiting debris from some comets, and the grains burning up in our atmosphere create meteors.

Among the annual sky-shows, the Leonids shower is like a temperamental rock star: In most years it delivers a modest show, with rates of about 15 shooting stars an hour.

In other years, however, the Leonids can suddenly erupt in spectacular meteor storms, with rates of more than a thousand meteors an hour.

That's because the trail of comet debris that creates the Leonids is uneven. The parent comet, Tempel-Tuttle, nears the sun every 33 years, leaving behind fresh clumps of material.

"In exceptional cases, the Earth will dive right through a very fresh trail lain down by the comet, and rates will be truly astronomical." said Geza Gyuk, an astronomer at the Adler Planetarium in Chicago.

The Leonids shower of 1833, for example, saw as many as a hundred thousand meteors an hour—equal to an average of 30 meteors a second, Gyuk said.

2009 Leonids: Modest but Still Worth It

For the 2009 Leonids, experts are forecasting a more modest but still notable sky show, as Earth brushes a 62,000-mile-wide (100,000-kilometer-wide) cloud made of debris left behind from cometary passes in 1467 and 1533.

As with any meteor shower, there's no need for fancy optical equipment to enjoy the show, NASA's Cooke added.

"The best way is to use your unaided eyes so that you can take in as much of the overhead sky as possible," he said.

"Simply lie back, arm yourself with some warm blankets and hot chocolate, and just look straight up."

There's also a facebook page for the Leonids meteor shower with more than 800,000 members.


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