Our Window on Nature

Vision at night is difficult at best, whether you are watching wildlife or searching the sky for meteor showers. But it always seems you need just a bit more light to check the settings on your camera. Or to find the position of a constellation on your star map.

The problem is that flipping on a flashlight ruins your night vision. It takes about 15 minutes for your eyes to adapt to the dark and see detail, and only a second or so of bright light to undo the process. Fortunately there is a solution.

Dim red light has only a minor effect on our vision at night, so a red flashlight allows you to check what you just wrote in your notebook and still look up to see the animals that have better night vision than we do. And the animals are less disturbed by red light.

I’ve seen advertisements for red flashlights, but a less expensive solution is to cover a light source with red cellophane or plastic. When I couldn’t find any locally, I bought a transparent reddish-pink file folder at a stationary store. Two layers did the trick. Enough light to see, but not enough to ruin my night vision.

What more could you ask? Warm summer weather — a new moon (the darkest night) — and one of the most consistent meteor showers of the year. If you’re willing to give up a little sleep, this weekend should be a wonderful show.

On the night of August 12th and the morning of August 13th the Perseid meteor shower should reach its maximum, with the potential of over a meteor a minute. The display occurs as the earth passes through the debris trail left by the Swift-Tuttle comet.

Small meteors enter the earth’s atmosphere every day, but only during a meteor shower do enough appear that you can be sure of seeing them. We actually entered the edge of the Swift-Tuttle trail back in mid-July, so the number of shooting stars has been increasing nightly. If you can’t catch the featured event on Sunday night and/or Monday morning, there are still more meteors than usual just before and after that date.

On August 12th (Sunday) the show gets a slow start around 9:00 pm with what are called Earthgrazers. According to Bill Cooke of NASA’s Meteoroid Environment Office these are “long, slow and colorful; they are among the most beautiful of meteors,” but you will probably only see several of them per hour.

The frequency of meteors keeps improving throughout the night, with the most concentrated portion of the shower occurring before dawn on Monday morning. Although some of the brightest meteors will be visible from urban locations, try to get away from city lights. Give your eyes about 20 minutes to adjust to the darkness, and then watch the darkest portion of the sky.

The photograph of the Perseid Meteor Fireball shown above was taken at Joshua Tree National Park by Wally Pacholka in 1999. Winner of both a Time Magazine and a Life Magazine “Picture of the Year” award, Wally has a spectacular web site featuring comet and meteor photography. Check it out at http://www.AstroPics.com/.

These may be the longest nights of the year, but as seen from space the world is covered with lights. And that makes stargazing and watching meteor showers more difficult.

Tonight is the middle of the three day meteor shower called the Ursids. It’s not one of the brightest, but still there may be as many as 15 meteors streaking across the sky each hour.

These fragments came from Comet Tuttle, although their name comes from their apparent direction - the constellation Ursa Minor, better known as the Little Dipper. Don’t worry about looking in any exact location, but generally face towards the North.

Although this is a minor meteor shower, the conditions will be good this year since the moon won’t get in your way. But it will be more important than usual to get away from the city lights. The best viewing time may be during the hour before dawn. Get up a little early and wear your warmest coat.

Watching the night sky can be fascinating any time of year, but during meteor showers it takes on the characteristics of a fireworks show. But just what is the object that causes all the excitement?

Let’s start with the name, because it changes depending on where you find it. While they are still out in space they are called meteoroids. As they flash though the sky on their way to the earth they are called meteors. And if they don’t burn up in the atmosphere, when they reach the ground their name changes to meteorites.

Some meteors are made up of a stony substance, mostly silicate materials. Others may be an iron-nickel combination. Or perhaps it is a blend of the two. But this is material from outer space that intersects our path as the earth travels around the sun.

A few people collect meteorites as a hobby while others do it for the sake of science. The problem with meteorites, unless you just buy them on EBay, is to find them. To be successful you either need a lot of luck or must understand why certain locations are better than others.

Meteorites deteriorate just like other rocks and minerals on earth, but in very dry areas this process can take millennia. So when scientists want to search for these space visitors, they usually head toward the South Pole.

At first thought this might seem a strange place to look for a dry climate, but the pictures of ice that come to mind ignore the fact that the Antarctic is classified as a desert because of the lack of moisture – an almost complete lack of liquid water. This means that rocks, or in this case the meteorites, will resist deterioration for a very long time.

The average age of a meteorite found in Antarctica is about 4.5 billion years, and scientist say that most of these discoveries have been on the earth for between 25,000 and 65,000 years.

Since 1976 the Antarctic Search for Meteorites (ANSMET) has sent 20 search teams to Antarctica, collecting over 10,000 meteorites. A combination of wind conditions and shrinking ice packs provide concentrations of these space fragments found nowhere else.

There is a real advantage to looking for meteorites on an ice pack. In most areas of the world these hunks of rock can easily disappear – buried in the ground, behind a bush, or hidden deep in a forest. But on an ice pack, there is almost no place to hide. Add to this the contrast between a black piece of rock and a white background, and an ice field becomes the perfect area to search.

Most meteorites come from debris caused by collisions of larger bodies in the asteroid belt, but some are actually from the moon or from Mars, blasted into space by a grazing blow from another space visitor. Those from the moon were identified by comparing them with rocks collected by astronauts, while fragments from Mars were determined when the gasses held inside their bodies matched those collected by robotic travelers to the red planet.

If you can’t afford the time for a quick trip to McMurdo Station in Antarctica, you can join them vicariously on the ANSMET website at http://geology.cwru.edu/~ansmet/index.html. Lots of pictures and a great explanation of what they do.

Tonight and over the weekend may be a great time for meteor watchers. It’s the middle of the Leonid Meteor shower, and this year the show could be more impressive than usual.

As a comet travels in its circular path, it drops off small particles which, over centuries, may eventually trail through the comet’s entire orbit. When the earth intersects this path you have a meteor shower. We pass through the orbit of the comet Tempel-Tuttle every November.

The picture on the left is of a Leonid fireball, taken from a DC-8 during the 2002 meteor shower. You can’t get quite that good a view from the ground, but some years meteor shows are truly impressive.

There’s almost no moon this weekend, so there won’t be much visual competition. If you can get completely away from city lights you can see twice as many meteors. The best times should be just before midnight. Just remember — dress warm.