Thursday, August 4, 2011

The Ellensburg sky for the week of 8/6/11

Saturday: It’s a moonless August morning. The first remnant of dawn has not appeared yet. Suddenly, you notice a large softly radiant pyramid of light in the east sky. The base of this ghostly triangle is along the east horizon and the peak stretches two or three fists held upright and at arm’s length above the horizon about two hours before sunrise. Don’t be scared. It’s not really a ghost. It is an effect called the zodiacal light. This light comes from sunlight reflecting off dust grains in our solar system. The effect is the most visible when the band of constellations called the zodiac makes a steep angle with the horizon. You need a clear dark sky with no haze or light pollution to see the zodiacal light. At its brightest, the zodiacal light rivals the light of the central Milky Way. This is one of the best times of year to see the zodiacal light in the morning.
This is also one of the best times of the year to see meteors. The Perseid meteor shower peaks this week.

Sunday: The Moon seems to move with precision tonight, moving between the head and the heart of Scorpius the celestial scorpion. Antares, representing the heart of the scorpion, is about a half a fist to the lower left of the Moon at 11 p.m.

Monday: The NASA probe called Dawn is orbiting the asteroid Vesta. Go to for more information about the Dawn mission and to see some fascinating photos of Vesta. Go to your binoculars to see Vesta for yourself in the constellation Capricornus. First find Deneb Algiedi, the brightest star in the constellation, two fists above the southeast horizon. Place this star in the upper left portion of your field of view, at the 10 o’clock position. Then move your binoculars toward the 4 o’clock position until two fairly bright stars come into your field of view. These two stars are close together, aligned diagonally, about half as bright as Deneb Algiedi. Next, place these stars in the upper left portion of your field of view, at the 10 o’clock position. Then move your binoculars toward the 4 o’clock position until a star about half as bright as these two comes into your field of view. Finally, move this star to the bottom of your field of view. Vesta will be near the middle of your field of view. It is about a finger width above this star, called 24 Capricorni.

Tuesday: Astronomers from the Beijing Planetarium recently identified a 30-ton meteorite in Northwest China. Just like asteroids such as Vesta, meteorites provide clues to the formation of the Solar System. Sometimes we spend millions of dollars on space probes to search for the evidence. Sometimes the evidence comes to us free of charge. See for more information.

Wednesday: Had the script been written a little differently for a well-known Robin Williams movie, we might have heard Mr. Williams shout, “Goooood Morning Orion the hunter”. Orion is typically thought of as a winter constellation. But, it makes its first appearance in the summer sky. The lowest corner of Orion’s body, represented by the star Saiph (pronounced “safe”), rises at 4:30 a.m., well before the Sun. By 5 a.m., Orion’s belt is about one fist above the east-southeast horizon.

Thursday: Saturn is less than a fist above the west horizon at 9:30 p.m.

Friday: The Perseid meteor shower peaks late tonight and early tomorrow morning. The meteors appear to come from a point just below the W of the constellation Cassiopeia. This point is about two and a half fists above the northeast horizon at 11 p.m. By 4 a.m., the peak time, this point is about seven fists above the northeast horizon. If you fall asleep or forget to set your alarm, you will be able to observe this shower from midnight to dawn for a few days before and after tonight in about the same location in the sky. The Perseid shower is one of the longest lasting showers. With dark skies, you can see up to 100 meteors per hour in the late night and early morning hours all week. Unfortunately, the nearly full Moon will obscure all but the brightest fireballs. As your Mother might say, dress warm and sit in a comfortable chair for maximum enjoyment. These meteors are sand to pea-sized bits of rock that fell off of Comet Swift-Tuttle. They are traveling about 40 miles per second as they collide with the Earth and burn up in the atmosphere. For more tips about meteor watching, go to

The positional information in this column about stars and planets is typically accurate for the entire week.

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