Saturday, August 7, 2010

The Ellensburg sky for the week of 8/14/10

What's up in the sky 8/14/10

Today: 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.

Sunday: Mars, Venus, and Saturn are close together low in the western sky all week. Venus is by far the brightest of the three planets. It is a half a fist held upright and at arm’s length above the west horizon, a little bit south of west, at 9 p.m. Mars is about a finger’s width to the upper left of Venus and Saturn is less than a fist to the right of Venus.

Monday: It’s time to sing along with a holiday classic: “Oh, the weather on the Sun is frightful. But the aurora is so delightful. Well, the Sun is active and hot. Let it spot, let it spot, let it spot.” The Sun seems to finally be waking up from its sunspot slumber. On August 1st, the sunspot region 1092 triggered a huge coronal mass ejection (CME) that shot out from the Sun at a speed of more than 600 miles per second. A CME is plasma consisting mainly of electrons and protons. When these charged particles interact with the Earth’s magnetic field, they produce the colorful phenomenon known as the aurora. Basically, increased solar activity means a more active Sun which produce more CME which leads to increased aurorae.

Tuesday: Antares is about a finger’s width to the lower right of the Moon at 9 p.m.

Wednesday: Mars is still about a finger’s width from Venus and a half a fist above the west horizon at 9 p.m. But notice that they have both moved eastward away from Saturn with Venus having moved a little more.

Thursday: This evening, Venus is as far away from the Sun in the sky as it will get this orbital cycle. What is this "farthest away" point is known as the planet’s greatest eastern elongation. As you have noted all week, Venus is a half a fist above the west horizon at 9 p.m. Over the next two months, Venus will move toward the Sun in the sky. By the end of September, it will be lost in the glare of evening twilight.

Friday: Fomalhaut, the bright star in the Piscis Austrinus, the Southern Fishes, is about one fist above the southeast horizon at midnight. It is the southernmost bright star visible from Ellensburg and other locations near 47 degrees north latitude.

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

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