Thursday, June 2, 2011

The Ellensburg sky for the week of 6/4/11

Saturday: In 1979, the group Foreigner recorded the song “Head Games”. They could have been singing about the constellations Hercules and Ophiuchus when they said “head games, it’s just you and me baby, head games, I can’t take it anymore” because the heads of these two constellations have been right next to each other in the nighttime sky for all of human history. Each head is represented by a star bears an Arabic name that means "the head." In Hercules, it's Ras Algethi (head of the kneeler); in Ophiuchus, Ras Alhague (head of the serpent charmer). At 11 p.m., Ras Alhague, the brighter of the two, is a little more than four fists held upright and at arm’s length above the southeast horizon. Ras Algethi is about a half a fist to the upper right of Ras Alhague.

Sunday: Jupiter is one fist above the east horizon and Mars is a half fist above the east-northeast horizon at 4:30 a.m.

Monday: Venus, named after the Roman goddess of love, is spending time near the seven sisters for the next few mornings. Not that there is anything wrong with that. The seven sisters, also known as the open star cluster the Pleiades, is a group of about 100 young stars – 50 million years old – in the constellation Taurus. Yes, 50 million years is young for stars. The Sun is about five billion years old. The seven sisters are named after the daughters of Atlas and the nymph Pleione and are nymphs themselves, companions to Artemis. According to Greek mythology, several important gods such as Zeus and Poseidon had affairs with the seven sisters. Are your children reading this? Put them to bed so they can wake up at 4:30 a.m. At this time, Venus will be a few fingers above the east-northeast horizon and the Pleiades will be a few fingers to the upper left of the Pleiades. Over the next few days, Venus will move lower in the sky and move underneath the Pleiades.

Tuesday: Nearly 400 years ago, Galileo viewed the Pleiades star cluster through his telescope and saw that the seven or so stars in the region visible to the naked eye became many more. There are two main types of star clusters. Open star clusters are groups of a few dozen to a few thousand stars that formed from the same cloud of gas and dust within our galaxy. Stars in open star clusters are young as far as stars go. Globular clusters are groups of up to a few million stars that orbit the core of spiral galaxies such as our own Milky Way. One of the most well known star clusters is the globular cluster in Hercules, an object that is fairly easy to find with binoculars. First find Vega, the bright bluish star five fists above the east horizon at 11 p.m. Two fists above Vega is a keystone shape. Aim your binoculars at the upper left hand star of the keystone. The globular cluster is one third of the way to the rightmost star of the keystone. It looks like a fuzzy patch on the obtuse angle of a small obtuse triangle. If you don’t know what an obtuse angle is, you should not have told your teacher, “I’ll never need to know this stuff”.

Wednesday: Tonight’s first quarter Moon is in the constellation Leo the lion.

Thursday: Saturn is one fist to the upper left of the Moon at 10 p.m.

Friday: Mizar is a well known binary star in the constellation Ursa Major. You can find it at the bend in the Big Dipper handle, nearly straight overhead at 10 p.m. tonight. Its name is Arabic for waistband. Mizar has an optical double called Alcor which is less than a pinky width away and can easily be seen with the naked eye. Optical doubles are stars that are close together in the sky but do not orbit a common center of mass as true binary stars. Not wanting to deceive sky gazers who call Mizar a binary star, two stars that DO orbit a common center of mass, Mizar actually is a binary. It was the first binary star system discovered by telescope. Mizar A and Mizar B are about 400 astronomical units apart from each other and about 80 light years from Earth. 400 astronomical units is about 10 times the distance between the Sun and Pluto.

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

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