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A Sudden Arc of Brilliance

A bright streak across the sky heralds the end of a stone from deep space.

 

Last Friday night, I had the pleasure of observing with a group of children and their parents far up in Sherman, CT, right at the border with New York. The skies were similar in darkness to my home location in Southbury, but we were in a large open space with nearly clear horizons, a great treat for me, since my yard is surrounded by nearby trees.

After completing the setup and alignment of the telescope, I was beginning to describe the next object we were going to observe, when out of the corner of my eye I caught a great brilliant arc far off to the north, growing brighter as it approached the horizon. Before vanishing in the distance, the falling object broke apart into at least 3 pieces.. It was all over in a matter of a second or two. The brightness of this object outshone the quarter moon that was sinking toward the west. This was the brightest meteor I have ever seen in my many years of observing.

Most of us are familiar with meteors, romantically described as shooting stars. You may have had the luck to have seen one or more meteor showers in your lives, when dozens or more of these fast-moving streaks of light can be seen in an hour. Very bright meteors - that appear brighter than the brightest planet (Venus) are labeled fireballs. Most of the larger meteor showers include large numbers of fireballs.

What we saw that night, however, was a bollide. A bollide is significantly brighter than a fireball, can be seen to break up into smaller bodies near the end of its descent to Earth, and will be accompanied by an audible explosion if you are near enough to the falling object. Even bollides, however, rarely reach the ground as meteorites, having disintegrated into dust thousands of feet above the ground.

So of what are meteors made, and from where do they come? As we have discussed previously, the meteors we see during meteor showers have come from the gradual evaporation of comets as they pass near the Sun, leaving behind sand in their wake.  However, most of the brighter, larger, meteoric bodies are not associated with comets, but are independent rocks formed from the primordial cloud of gas and dust from which the Sun and planets were created over 4 billion years ago.

Meteors represent samples of the building blocks of the solar system, unchanged by the action of weather, volcanic melting, or geological compression and metamorphism.  From collections of meteorites - the meteors that actually reach the ground in pieces larger than dust - we can learn a great deal about the composition of the early solar system. 

By far the most common meteorites (chrondites) are similar in composition to the rocks in your backyard, found throughout the crust and mantle of the Earth.  A subgroup of chrondites resemble the composition of the Sun, without the gases present, of course.  About 5% of meteorites are composed of a dense mixture of iron and nickel - the same materials of which the cores of the Earth and other rocky planets consist.

Meteors enter Earth's atmosphere at over 20,000 miles per hour, and heat up to several thousand degrees in a matter of seconds.  They begin to glow between 70 and 35 miles above Earth, and usually dissipate several miles above the ground.  Despite common thinking, the meteor is very rapidly slowed by the lower atmosphere, and stops glowing more than 10 miles above the ground, and all but the most massive meteorites hit the ground at less than 100mph.  The burning off of the outer layers while the meteor is glowing followed by the much slower descent to the ground means that the average meteorite, if found immediately after impact, is only slightly warm, and can be easily handled.

Meteors are continually falling on the Earth.  Several hundred tons of meteor material  are deposited on the Earth every day, mostly in the form of dust.  Approximately 4,000 fireballs occur each day, though only a very few are observed by humans - half would occur during daylight hours, and another quarter in the deep night.  It is estimated that about 100 meteorites reach the ground daily, of which approximately 12 would be in areas man inhabits.

The American Meteor Society collects reports of fireballs and correlates them by time and location to attempt to identify individual events.  Last Saturday morning, after my observation the night before, I found that the AMS had over 70 sightings of this massive meteor, ranging from the Catskill area of New York up through Ottawa.  The event seemed to be centered in southern New Hampshire. 

This post is contributed by a community member. The views expressed in this blog are those of the author and do not necessarily reflect those of Patch Media Corporation. Everyone is welcome to submit a post to Patch. If you'd like to post a blog, go here to get started.

Denise Kopasz October 01, 2012 at 12:00 PM
Thanks for this article. I have some friends in NY that saw something just like this on the Thruway. I sent them the article
Aaron Turner October 03, 2012 at 01:38 AM
I discovered this afternoon that there is much more to the story of the bollide I saw on the 21st. A good freiend of mine, fellow amateur astronomer, forwarded me an article from Sky and Telescope that elaborated on this very unusual event. About 2 hours and 35 minutes prior to my sighting, a very large bollide was seen throughout Europe and the United Kingdom. Videos and photos taken of that event can be found in several places - the meteor moved quite slowly across the entire sky, heading northwest. From the hundreds of recorded observations, researchers have been able to determine that this meteor skimmed across the top of our atmosphere, and did not disintegrate or crash to the ground, but escaped back into space. Such "grazing" meteors are not uncommon; what happened next however has never been observed before. The departing meteor had been slowed to such an extent that it did not escape Earth's gravity, but entered an orbit about the planet. After completing a single orbit, it crashed back into the atmosphere over Maine and finally disintegrated over New England, becoming the bollide seen that night. Truly amazing. Had the meteor been travelling just slightly faster, or arrived at a slightly different angle, Earth would have picked up a new satellite, at least temporarily.
Aaron Turner October 03, 2012 at 01:42 AM
In fact, I just realized that the photo accompanying my article above is indeed of the first pass of the bollide over England.
Jaimie Cura (Editor) October 03, 2012 at 01:50 AM
Aaron, this might be one of the coolest things you've ever said here and you've said a lot of cool things!
Ellen Dages October 03, 2012 at 01:54 AM
Interesting photos.
Steven DeVaux October 03, 2012 at 09:53 AM
Excellent article and explaination Aaron. Thank you.

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