Monday, June 15, 2009

The Ellensburg sky for the week of 6/20/09

Saturday: Today is the first day of summer, the day that the Sun reaches its highest declination (the official name for sky latitude) of 23.5 degrees above the celestial equator. The celestial equator is the line that divides the northern sky from the southern sky. In Ellensburg, the Sun is about seven fists held upright and at arm’s length above the south horizon at 1:00 p.m. (noon standard time). Contrary to popular belief, the Sun is never straight over head in Ellensburg or anywhere else in the 48 contiguous states. The northernmost portion of the world where the Sun can be directly overhead is 23.5 degrees north latitude. In ancient times, the Sun was in the constellation Cancer the crab on the first day of summer. Hence, 23.5 degrees north latitude has the nickname "Tropic of Cancer". Because the Earth wobbles like a spinning top, the Sun's apparent path through the sky changes slightly over time. Now, the Sun is in the constellation Taurus the bull on the first day of summer. However, citing the high cost of revising all of the science books, geographers are not changing the name of 23.5 degrees north latitude to "Tropic of Taurus". The first day of summer is often called the summer solstice. However, astronomers refer to the summer solstice as the point in the sky in which the Sun is at its highest point above the celestial equator. Thus, summer starts when the Sun is at the summer solstice point. This year, that happens at 10:45 p.m.

Sunday: In this tough economy you need to get up early to tweak your resume, write those cover letters, fill out applications, and look at the planets Venus and Mars. At 4 a.m., Venus and Mars are one fist above the east horizon. Mars is about a finger width to the upper left of Venus. They will remain in this location throughout the week. So take a break from the job search and look at the sky.

Monday: In 1981, the well known astronomy rock group Blondie released The Tide is High in two versions: the radio version and the astronomy version. In the astronomy version, Debbie Harry sang: “The tide is high ‘cause the moon is new. Higher still when the moon’s close, too.” Tonight's moon is new. The new moon is the phase where the Moon is directly between the Earth and the Sun. That means the moon and Sun are both stretching the Earth in the same direction causing the ocean water in line with the Sun and moon to be pulled upward. In addition, the moon is at perigee early tomorrow morning. Peri- means close and –gee refers to the Earth so this is the day of the month when the moon is closest to the Earth. This accentuates the upward pull on the water and makes the tides really high. Blondie hoped to release a third version titled “The Tide is Really High”. But, the record label finally said, “enough is enough.”

Tuesday: Jupiter is finally making its way into the evening sky. It rises just before midnight over the east-southeast horizon. By 1 a.m., it is one fist above the southeast horizon.

Wednesday: Summer is nearly here. How do I know? Because my kids are home from school. Also, because the Summer Triangle is fairly high in the eastern sky at 10 p.m. Vega, the third brightest star visible from Ellensburg, is about five fists above the east horizon. Deneb, at the tail of Cygnus the swan is about three and a half fists above the northeast horizon. The third star in the triangle, Altair, in Aquila the eagle is two fists above the east horizon.
If you want to put somebody off, tell them to wait until Deneb sets. At Ellensburg’s latitude of 47 degrees, Deneb is a circumpolar star meaning it never goes below the horizon.

Thursday: Two weeks I wrote about Mizar, the bright star in the bend of the Big Dipper handle. Don’t confuse it with its rhyming brother Izar in the constellation Bootes. Izar is also a binary star with about the same apparent brightness. And both were featured in different episodes of Star Trek. Izar was featured in the Star Trek episode “Whom Gods Destroy” from the original series. It is the base of Fleet Captain Garth, a former big shot in the federation and one of Kirk’s heroes before he went insane. Garth kidnaps Kirk and Spock before eventually being out smarted. Mizar doesn’t play as big a role in its episode. It is the star of the home world of one of the alien species in The Next Generation episode “Allegiance”. Izar is one fist above the bright star Arcturus and seven fists above the south horizon at 10 p.m. Mizar is seven fists above the northwest horizon at this time.

Friday: Venus, the Moon, and the bright star Regulus make an obtuse triangle in the western sky at 10 p.m. Regulus is a little less than one fist to the right of the Moon and Saturn is a little more than one fist to the upper left of the Moon.

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

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