Wishing on Falling Stars
Friday, November 24 2006 @ 08:00 pm EST
Contributed by: bobmoody
The usually productive Geminid meteor shower reaches its peak each year on the evening of December 13 & 14. In 2006 this is the middle of the week. Geminid meteors are occasionally bright, relatively slow compared to other showers during the autumn months, and best of all, they will restore your faith in meteor showers, at least, as long as the clouds stay away!
UPDATE: 12/14/06 The Geminids did NOT disappoint this year! AOAS members in attendance at Coleman Observatory were treated to rates of at least 90/hr, and the rates could have been as high as 110/hr. Along with the pleasantly warm temperatures, an exceptionally clear and steady sky, and lots of viewing the universe with our 14" computerized telescope, we all enjoyed ourselves, some until nearly 2:30am. We won't likely see another meteor shower this good again for a while, so if you missed this one, you missed a really good one!
November 12, 1833 was just another day, but that night brought the end of the world! On that evening the greatest meteor STORM in human history occurred with an estimated fall-rate of up to 300,000 PER HOUR! Every place that witnessed the spectacle saw people fearing that the end of the world was at hand. This gigantic event was witnessed from Europe across the North Atlantic and well into the middle of North America, and it is said to be solely responsible for the birth of modern meteor science.
|Look to the ENE horizon at about 8:00pm on Wednesday, December 13, 2006. Orion will be to the SE of Gemini, and about as high above the horizon. Kick back in a lounge chair or in a thick, warm sleeping bag and just stare at as large of an area of sky as you can take in. Expect to see 50 meteors every hour originating out of the area near Castor early on. Rates will increase to 70/hr and may occasionally reach 90/hr as Gemini rises to near the zenith around 1:00am on Dec 14. |
The 1833 outburst of activity was from the Leonid meteor shower. The Leonids fall from an area in the "head" of the constellation Leo every November 17-18. Even the east coast of the US saw rates of fall in 1833 on the order of a few thousand per hour, and needless to say, most people who witnessed that event would never be the same again. Many were convinced that what they were seeing was a direct effect from the Hand of God.
At the time, science had only recently begun to accept the notion that meteorites were pieces of rock and metal that fell to Earth from outer space. It simply seemed too counter-intuitive to be true, at least as far as most people were concerned, and there were some influential individuals in that group. One such person, a scientist who was also our second president of the United States, Thomas Jefferson, supposedly remarked after a recent fall of a small stone meteorite in Connecticut, "I'd [sooner] believe that two Yankee professors would lie than [accept] that stones would fall from heaven."
This statement is believed to simply be folklore, but it reflects the feelings of the majority of laypeople and even most scientists of the day. Sometime around that same period in history, the connection between meteors and comets was also established. Those who studied the orbital motions of comets recognized that the thousands of meteors which fell in 1833's Leonid storm bore a remarkably close resemblance to the orbittal path of comet Temple-Tuttle. And, it just so happened that the comet was making its normal 33-year periodic visit to the inner solar system at around the same time. The Leonids sometimes produce HUGE meteor storms about every 33 years when Temple-Tuttle returns. Suddenly, here was the connection between meteors and comets right in the face of all who understood orbital mechanics based on mathematical formulae. Now we knew...annual meteor showers originated with the passages of comets through the inner solar system.
|One of three images I took of the Leonid meteor shower of November 18, 1998, the night of 100 fireballs! This one ended in a "terminal burst" which is when a meteor briefly fades away and then suddenly bursts into light as it is completely consumed by the frictional heating with air molecules. Can you see the faint red horizontal streak of color near the trees? That's a "train" of still glowing air molecules left over from another recent bright fireball only minutes before I took this image.|
Meteors from ALL showers are simply that dusty material shed from their cometary parent-bodies as they pass through the inner solar system.
I apologize for my drawing above, but without it I'd be forced to try and help you envision where the Geminid meteor shower comes from with mere words.
|Earth's orbit takes us once around the Sun each year. If a comet has passed through the area where our orbit lies, we pass through dust particles left behind from that comet. We pass through the dust trails of several past comets every year.|
A basic understanding of comets is needed here, and we must start with the elemental make-up of the comet itself. Comets are chunks of frozen water-ice and a wide mix of frozen gasses, as well as millions of tons of small pieces of dust and metal fragments. A typical comet is usually about the size of a large city, but some are thought to be up to many dozen miles in diameter. The general description of comets being huge "dirty snowballs" is absolutely accurate, and yet they are some of the smaller members of our solar system. Their apparent size is covered in the "read more" area.
Sometimes comets are set in motion from their origination point 10-billion miles away, towards the general direction of our Sun by a passing star or a gravity wave. Once this occurs, nothing can stop it, and the (frequently) odd-shaped comet nucleus will begin to form a dusty and gaseous halo around itself as the volatile frozen gasses are heated by the Sun's energy as the comet draws nearer. The Sun's solar wind is always blowing outward in all directions, and this energy causes the dust and gas to be swept backward away from the comet's head causing the characteristic "head-and-tail" appearance. No matter which direction the comet is moving, the energy from the solar wind ALWAYS forces the tail to point away from the Sun. A comet's tail points away from the Sun when the comet is inbound, and then the head actually follows the tail after it rounds the Sun and once again moves outbound through the middle-to-outer solar system.
Click read more for the rest of this story.
A comet's passage through the inner solar system when the frozen gasses are constantly being ejected releases any bound-up dust as it goes. Some comets are "dustier" than others, but all comets litter their orbital paths with more freshly expelled dust every time they make another passage. Comets that periodically return for more trips around the Sun are called, of course, periodic comets. These comets have return-times of 200 years or less. Other comet's orbits won't see them return for thousands of years, or more, if at all. This dusty material can spread out over very wide areas due to the explosive release of the volatile gas expelled from the comet due to the Sun's heating. In fact, a comet's "head" can easily swell to 50,000 miles wide, while their "tails" can reach lengths of 100 million miles or more! ALL of the dust shed from a comet continues to travel in the same orbital path as the comet that released it. Sometimes, Earth may pass through some of this dusty debris, and then we'll begin to see a shower of meteors each year at about the same time every 365 days.
|Another meteor from November 18, 1998. This one is dimmer, due to its smaller size, and careful examination will reveal a few more still-glowing ghostly "trains" of glowing air molecules ( the "U"-shaped one is easy to see above this meteor) where they'd only recently passed out of existence. |
The dust particles are typically the size of a grain of sand, up to maybe as big as a walnut, and more rarely they may be as large as a basketball! The bigger the particle, the brighter the light created by it when it enters our atmosphere, causing it to glow from friction with air molecules in the upper atmosphere.
On the evening of November 18, 1998, myself, Honorary AOAS Lifetime Member Jay Hilgartner, Joe Roam and three other people spent the entire, long night watching the most amazing spectacle of brilliant meteors and huge fireballs that any of us had every seen. In fact, most people in North America who witnessed that event had never seen anything like it before. Careful study of that shower, along with comparisons of the same shower every year for more than 100 years, allowed people who study those things to announce that we had passed through a "band" of much larger meteor particles than are usually seen.
The Leonids produce very high fall-rates in the thousands-per-hour range every 33 to 34 years as Earth passes through a particularly thick area of normal-sized particles. Other braided bands of dusty material had been suspected for years as well. But the outrburst of giant fireballs in 1998 was estimated to be caused by the occasionally basketball-sized object that screamed into brilliance about every 10-15 minutes between 12:00am and 2:00am of November 19. In all, we counted an amazing 950 meteors that night between midnight and sunrise the next morning, about 6 hours later. The highest fall-rate we saw was the 206 meteors we counted between 1:00am and 2:00 am. It was an awesome thing to see!
|This curly-Q is actually a long-lived “train” of still glowing air molecules left over from a magnificently bright meteor nearly 25 MINUTES after the meteor extinguished itself. This was the brightest meteor I have ever seen in my lifetime, as well as the longest lasting train I’ve ever seen. We were able to continue seeing the slowly fading remnants of this train for nearly 45 minutes after the meteor! |
I had been trying for nearly a decade to capture a meteor on 35mm film. Its easy to do, they said, by just pointing a camera with a short focal-length lens at an area of sky during the times of a meteor shower. The camera must be setup on a tripod, with a cable release, and have a manual capacity to allow the shutter to be opened for as long as the photographer wishes to expose the frame. I had all that, and the patience to keep trying after the first 3 or 4 years of NO luck during several hundred attempted frames. In about 11 years of trying, I'd caught one tiny, miniscule meteor a couple of years before 1998, but on November 18 that year, I actually caught FOUR meteors at various times in various parts of the sky. These images in this story are mine from that night now 8 years gone.
Go out to a dark location on Wednesday, December 13-14, and simply gaze up at a clear pattern of stars in the eastern sky at around 8:00pm. Most meteor showers don't get really active until their points of origination, called a radiant, rise above the horizon. Gemini rises at around dusk, so these are all-night-long meteors! Dress warmly, drink non-alcoholic beverages such as coffe, tea or hot chocolate, kick back on a sleeping bag or in a chaise lounge and just watch. No telescopes, no binoculars, just your eyes and a clear sky will give you an experience you may never before have witnessed. If you're lucky and the conditions cooperate, I think you'll be pleasantly surprised as you wish upon [many] falling stars.