Although the Earth has survived thus far, there have been some close calls.  To date, scientists have confirmed 172 locations on Earth determined to be “impact structures” from meteors, asteroids, and pieces of comets. Two notable impacts are the devastation at Tunguska near the turn of the century, and the huge craters near Flagstaff, Arizona where an asteroid traveling at 26,000 miles per hour pummeled the Earth approximately 50,000 years ago.

Future objects descending onto our planet may be more than our Earth can handle.  Could a large asteroid with Earth in its sights be our doom?  Or perhaps a star a million times bigger than ours exploding and enveloping everything in its path?  Is the destruction of Earth eminent?

Violent Universe explores all of these questions and allows viewers to witness the raw power of the cosmos.  Experience the full intensity of our Hansen Dome Theatre with sprawling stars capes and phenomenal cosmic imagery.  Violent Universe: Catastrophes of the Cosmos opens February 18, 2011 and will play daily at 1:30 and 3:30 p.m., and at 6:45 p.m. on Sundays, Mondays, Wednesdays and Fridays.  View the trailer or purchase tickets here.  Admission to this program is complimentary for current Clark Planetarium members.

There is a predicted peak rate of 120 meteors per hour this year. The high peak rate, no Moon in the sky at peak time, and peak time occurring in the pre-dawn hours (mountain time) makes this meteor shower one not to miss.

Associated Press image of a meteor in the night sky.

The shower is named for the constellation Gemini, which contains the radiant of the shower. Gemini is high in the south, near the zenith at 2 am on the morning of the 14th. The radiant is the source point for Geminid meteors. Meteors will be visible across the sky, but the familiar streak of light can be traced backward to the constellation Gemini. No need for a telescope or binoculars. Just bundle up warm and watch the entire sky.

The Geminid shower is rather unique in that its origin is an asteroid, not a comet. In the 1980s it was confirmed that asteroid 3200 Phaethon was the origin of the Geminid meteor shower, the only major shower to be associated with an asteroid rather than a comet.

If you do get up real early for this shower, you should also note that Saturn and Venus will rise in the southeast in these early morning hours. Actual rise time will depend upon your view of the eastern horizon and the angle relative to mountains, but look for Saturn after 2:30 am and Venus after 4 am. Saturn is a dirty yellow color and a decent magnitude +1. Venus is brilliant at magnitude -4.6, just about the brightest it can be.

Here’s hoping for clear skies!

The Orionids are the result of Halley’s Comet, which last passed by Earth in 1986 and won’t return again until 2061. The name ‘Orionids’ comes from the constellation Orion, which contains the radiant of the shower.

created with Starry Night Pro 6 software

The radiant is the source point for Orionid meteors. Even though meteors can be seen across the sky, if you trace backward the familiar streak of light for a number of meteors, you will find that they converge in the constellation of Orion.

Earth passes through this particle stream every year about August 12. This year the peak of the Perseid meteor shower is August 12 at 6 p.m. MDT, only a few hours before nightfall. An observer away from city lights might see about 60 meteors per hour. Early morning observers can also see the planet Jupiter in the south-eastern sky. A thin crescent moon sets before 10 p.m., so moonlight will not interfere with observing the shower this year.

Where is the best place to look? Look up. While the meteors will appear to originate from the constellation Perseus in the northeast, they can be seen all over the sky. The best time to observe the shower is from about 1:00 to 5:00 a.m. (on the morning of the 13th) when Utah is facing into the meteor stream. If you cannot observe during those hours, do not despair, some meteors will still be visible as soon as the sky is dark.

The most important aspect of observing a meteor shower is to be away from city lights. No equipment is needed to observe, so leave the telescope at home. Meteor showers are best seen with the eyes alone, taking in as much of the sky as possible. However, a reclining lawn chair and mosquito repellant may help make the observing session more comfortable.

Regardless of the predicted peak hour, the best time to watch for meteors is during the pre-dawn hours (after midnight), your local time, when your position on the Earth is moving into the meteoroid stream. Meteors (commonly called ’shooting stars’ or ‘falling stars’) are actually little more than grains of sand, dust and small pebbles that burn up high in the atmosphere as they fall down to Earth at very fast speeds. The Perseids are traveling at around 60 kilometers per second (130,000 miles per hour!).

Meteor showers are the result of a passing comet. Comets are mountain-sized objects made of frozen gasses, water, and dirt. As the comet approaches and rounds the Sun, it sublimates (turns from a solid directly into a gas, like dry ice), creating a cloudy sphere, called the coma, around the nucleus. The solar wind pushes on the coma forming the long comet’s tail, which always points away from the Sun. It is the gritty particle material of the comet that we see as meteors when the Earth passes through this debris field left behind long after the comet has passed. The comet may not come back for many years, but we will enjoy the meteor shower at about the same time every year. The Perseids are the result of comet Swift-Tuttle, which last passed the Sun in 1993 and won’t be back for another 118 years.

The name ‘Perseids’ comes from the comet Perseus. As you watch Perseid meteors, all over the sky, you can trace backward the familiar streak of light seen. No matter which direction the meteor is headed, the streak of light can be traced backward toward the constellation Perseus. Doing this for several meteors will show that there is a point of convergence for all these backward-traced paths. This point, called the ‘radiant,’ which will be in Perseus.

No need for a telescope or binoculars. Just get comfortable, get out of the city if you can, and enjoy the Perseid meteors this week.

With New Moon on the 16th, there will be no moonlight to wash out the sky, making this year’s Geminids a shower worth watching Sunday night.

The Geminid shower does not originate from a comet, like other common meteor showers. In 1983, Asteroid 3200 Phaethon was confirmed as the parent body for the Geminid shower, the first time that a meteor shower was identified with an asteroid rather than a comet.

The shower is named ‘Geminid,’ referring to the constellation of Gemini, which contains the radiant of the shower. If you watch Geminid meteors, and trace backward the familiar streak of light, you will notice that all Geminid meteors trace back to a location in the Gemini constellation.

Meteors will be visible across the entire sky. No telescope or binoculars needed: Just dress warm, look up, and hope for clear skies.

If you saw it, please take a moment and post your comments below to help us present a clearer picture if the event so that we may continue to share it with others. What direction was it traveling from where you were? How long was the light trail it left behind? How long was the flash of light? What other information do you have that might help us learn more about it?

Thanks in advance for the posts. Its great events that help everyone remember to look up.

This week’s Cosmic Quiz winner is Mary Newland, who asked, “Every year I like to watch the Perseids meteor shower. If the meteors are continually being shed, why does the comet not cease to exist?”

That is a great question!

As a matter of fact, comets do cease to exist over time.

Let’s start with some background information on comets:

What is the life expectancy of a comet?

Comets can be thought of as large dirty snowballs. The core of a comet, known as the nucleus, is typically a several mile-wide lump of frozen water that also contains various amounts of frozen gasses such as carbon dioxide, carbon monoxide, methane, and traces of ammonia. Mixed into all these ices are small amounts of rock and dust. An assortment of tar-like hydrocarbon compounds covers the surface of the nucleus.

Nearly all comets follow huge looping orbits around the sun, spending almost all of their time in the dim, cold regions of space far beyond the outer planets. For many comets, the time between successive close approaches to the sun is measured in thousands of years.

Comets spend most of their lives far from the sun.

Even a “Short Period” comet like Halley’s Comet (above) with its 76 year orbit spends most of its time far from the sun.

A comet’s orbit will periodically carry it, briefly, to the inner solar system. In the toasty-warm inner solar system the heat from the sun causes some of the ices near the surface of the comet’s nucleus to sublimate, transforming the ices directly from a frozen solid into a gas.

The expanding ball of gas and dust forms the comet’s head, also known as the coma, which grows to become hundreds of thousands of miles in diameter.

As these ices turn themselves into gas they release into space the trapped dust and bits of rock that are embedded in the ice.

Comet Halley's 10 mile-long nucleus as imaged by the Giotto spacecraft in 1986.

Pressure from the sun’s light and magnetic field pushes the coma away from the sun, creating the comet’s tail, which itself can become tens of millions of miles long. All this from mountain-sized lump of dirty ice!

While a comet is in the inner solar system it is warmed by the sun and constantly sheds bits of dust and tiny pieces of rock. These drift through the solar system following roughly the same orbit as the comet.

Comet 73P/Schwassmann-Wachmann losing matter as it warms.

It is not uncommon for a comet’s orbit to intersect with Earth’s orbit, and our planet finds itself several times each year plowing through a region of space that’s been recently dirtied-up by a comet. For the few days during which earth passes through a comet’s orbit our world encounters an above-average number of meteors.

It’s sort of like driving your car through the countryside. There are always a few unfortunate bugs that will cross paths with your windshield, but occasionally you’ll encounter a hapless swarm of gnats. Splat!

That’s the way it is with meteor showers. The sky overhead in the wee-small hours of the morning is the “front windshield” of our planet as we zip through space at 60,000 miles per hour, and meteor showers are ill-fated collections of dust and gravel, shed by comets, whose orbits around the sun place them in front of us, where they meet their brief, fiery demise.

Astronomers estimate that a comet nucleus can survive anywhere from a few dozen to a few hundred passages around the sun before it has lost so much material that it no longer creates a coma and tail and is doomed to spend the next few billion years as an unremarkable asteroid.

Nucleus of nearly-dead Comet 9P/Tempel, imaged by the 2005 Deep Impact spacecraft.

Comet Swift-Tuttle, with an orbital period of 133 years, is the comet that is the source of next week’s Perseid Meteor Shower.  This comet’s life expectancy is thought to be only 50,000 years or so, which in astronomical terms is an eyeblink.

Now that we know that comets can indeed “cease to exist,” the really interesting question becomes, “If comets don’t last very long, then what replenishes the supply of comets to our solar system?”

That, dear reader, needs a whole ‘nuther blog post.

But I’ll give you a hint: “Oort Cloud.”

This shower could bring up to 60 meteors per hours, but a nearly-full Moon will wash out the dimmer meteors. Still, warming weather makes casual observation for meteors over the next couple of days a comfortable nightime activity.

The Aquarids are named for Aquarius, which doesn’t rise until about 3 a.m.