Thursday, July 27, 2017
The Ellensburg WA sky for the week of 7/29/17
Saturday: Hit the road Mercury. And don’t you come back no more, no more. For a few weeks, Mercury has been hitting the road and moving away from the Sun in the sky. Today, Mercury is as far away from the Sun as it will get on the evening half of this cycle. This is known as its greatest eastern elongation. Yet, this distance does not translate into good viewing because Mercury will be very low in the sky. Mercury is less than a half a fist held upright and at arm’s length above the west-northwest horizon at 9:10 p.m. Over the next few weeks, Mercury will move toward the Sun in the sky. After it passes in front of the Sun, it will appear in the morning sky by early September.
Sunday: At 9:50 p.m., Jupiter is one fist above the west-southwest horizon and Saturn is two fists above due south.
Monday: Do you want an easy way to find due north? A compass points to magnetic north, which is a few degrees off of true geographic north. Well, tonight’s your night. Capella, the brightest star in the constellation Auriga the Charioteer, is due north at exactly 9:39 p.m. It looks like a bright light on a pole on the north ridge because is only about three degrees above the horizon.
Tuesday: In Scotland, August 1 was known as Lammas, the festival of the first wheat harvest of the year. You can remember this by looking at Spica, named after the Latin word for “ear of wheat”, one fist above the west-southwest horizon at 9:30 p.m. August 1 is known as a cross-quarter day, a day approximately half way between an equinox and a solstice.
Wednesday: 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 in a week and a half. But you should see increased meteor activity for the next three weeks 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 dawn, this point is about seven fists above the northeast horizon.
Thursday: NASA just developed a faster and more cost-effective way to send a probe to a large solid metal asteroid. Psyche! Oh…. Did you think I was using the word “Psych” for its urban dictionary meaning of negating the statement before it? As in, “The writer of this column is a really smart guy. Psych.” No, NASA did just develop way to put a probe in orbit around the solid metal asteroid called Psyche four years earlier than originally planned. Thanks to a new five-panel x-shaped design for its solar array, NASA’s Discovery will gather more energy from the Sun and avoid the need for an Earth gravity assist. For more information about the Discovery mission to Psyche, go to https://goo.gl/rG6Qh7.
Friday: Venus is two fists above the east horizon at 5 a.m.
The positional information in this column about stars and planets is typically accurate for the entire week. For up to date information about the night sky, go to https://nightsky.jpl.nasa.gov/planner.cfm.