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Our Annual Summer Celestial Fireworks Show
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It's the time of the summer that meteor lovers love. Our annual summer celestial fireworks show, the Perseid Meteor Shower, has arrived. But rather than just looking up for meteors this year, use this time to get to know the summer skies, too.
First, though, a brief background on meteor showers.
When comets whiz around the sun, they dump a lot of dust. This debris travels along in pretty much the same orbit as the parent comet.
Some of these comet orbits intersect our own orbit. When Earth plunges through a comet's debris train, the dust slams into our atmosphere like bugs on a windshield. The friction with the atmosphere vaporizes the debris in flashes of light that we call meteors.
On the days of August 11 and 12, Earth passes through the big chunk of a debris train resulting in a meteor shower. The best time to "shower" will be after midnight early Monday morning when our side of the planet turns into the stream, resulting in the most meteors. A good Perseid peak might give us about 30 meteors an hour, but less where it is light polluted.
Unfortunately, you may be unwilling to stay up that late and will be meteor hunting before the midnight hour. Because Perseid sightings will be few and far between for you, this may be a good time to get to know some of the summer sky while you wait. Let's take a quick tour.
On
the evening of the 11th, a four-day-old crescent Moon will be setting
alongside a magnificently bright Venus. This Moon-Venus pose is one of
those aesthetic pleasures that happens several times a year, but never
ceases to command awe.
Try and actually see the "dark" side of the Moon, the non-crescent part. You'll notice it is just slightly lit, allowing you to see the whole disk of the Moon. This is due to "earthshine" which happens when the sun's light reflects off Earth's surface, dimly lighting the surface of the Moon.
Venus is about at its brightest now as it swings around the Sun in its orbit, passing us on an inside lane. The brightness of the Evening Star is due to its complete cloud cover. But she isn't covered in clouds made of water like our planet is --- those clouds are made of corrosive sulfuric acid.
Find the Big Dipper in the northern skies. Using the stars in the handle as pointers follow an imaginary curve, about one Dipper away, to the bright star Arcturus, a red giant seventy times bigger than the sun.
Keep following the curve over into the skies near the setting Moon to a big bright blue star called Spica. Spica spews out more energy in a minute than the sun does all day. Better look early, though; Spica sets about 9 o'clock.
Directly overhead later in the evening is the Summer Triangle, starring Deneb, Altair and bright blue Vega, the three of which make up the edges of the triangle. Each has an invisible binary companion star orbiting with it.
It's later in the evening that the Milky Way shows up in full glory, stretching from the south to the north. Those with binoculars can search the skies of the southern Milky Way and easily pick out abundant nebulae and star clusters.
The Perseid Shower is a great opportunity to see some really stunning meteors, to be sure. But use the night to get familiar with the rest of the spectacular summer sky, as well!
Questions or comments? Mark Ritter can be reached here.
Posted by Administrator at 2002.08. 3 02:40 PM | Comments (0)
