Stardate:08:12:98
Watching The Perseid Meteor Shower
Meteor showers are perhaps the easiest type of astronomical event to
watch, and arguably one of the most stunning. Not only can you view meteor
showers without a telescope or binoculars, but such instruments are almost
useless for shooting stars which travel so quickly across the night sky.
This is truly an event for the naked eye only.
The particles which make up a typical meteor are about the size of an
apple seed. As they plummet towards the Earth, they are heated by air friction.
Even the thin atmosphere far above the Earth can provide enough heat to
quickly incinerate these tiny stones into a blazing trail of light.
Although meteors (sometimes called shooting stars) have been seen throughout
history, it was unknown exactly what caused them. For centuries it was
believed that meteors were just an atmospheric event with no connection
to space. This is why the science of weather is called meteorology. Thomas
Jefferson himself did not believe that meteors were caused by rocks falling
from outer space. When a story was brought to him that two farmers had
seen a meteor fall right onto their farm, he replied "I would rather
believe that two Yankee farmers lied than to believe that rocks fall from
the sky.". No one's perfect.
Nine times each year our home planet races into comet debris, lighting
our skies with a shower of shooting stars. This week is one such week.
The Perseid meteor shower (caused by pieces from the comet Swift/Tuttle)
peaked in the early morning of the 13th, and will slowly taper off through
the third week in August.
Any clear night this week, go outside about 10 pm, and set up a chair
facing east/northeast. You should not have to wait long to see a shooting
star. At it's best, the Perseids this year should produce about one shooting
star per minute. The absolute best time for observing, however, is just
before dawn, when the meteors will be coming from nearly due east/southeast,
and 2/3 of the way above the horizon. Early risers will also be treated
to the sight of Venus and Mars huddled close together low on the east/northeast
horizon.
Some tips to make your observation a little easier are to bring some
carbohydrates with you for energy (for instance, a sandwich), a thermos
for drinks, and bug repellent. See if you can count how many meteors you
see within a given time period. Also remember to take regular breaks from
observing, perhaps for 10 minutes after every 50 minutes or observing.
Incidentally, just before a rock fragment enters our atmosphere, it
is called a meteoroid. While it is traveling through the atmosphere and
is visible as a shooting star, it is called a meteor. Only if it is large
enough to avoid destruction in the atmosphere and lands on the ground is
it called a meteorite.
If you have a telescope with a clock drive and a piggyback bracket,
you can mount the camera on top of the telescope. and turn on the drive.
Set the camera to bulb (the "B" setting), and expose for at least
a few minutes. The motor drive will turn the camera so that the stars will
not seem to move though the picture, but the shooting stars will. What
you will be left with will be a picture of a star field with (hopefully)
several meteors streaking through the frame.
Another meteor shower activity, is to record the number of meteors for
a given amount of time (30 minutes. say), and do that several times over
the course of the length of a shower. Now, compare the rate at which they
were falling at various times. Try this for several days before and after
the peak of meteor activity. Or, try it at various times of the night.
Were there more meteors early in the evening, in the middle of the night,
and just before dawn? Keeping in mind that the Earth is running into this
comet debris, do your findings make sense? Why, or why not?