Monday, May 18, 2009

The Ellensburg sky for the week of 5/23/09

Saturday: Ophiuchus (pronounced O-fee-u’-kus) the serpent holder rises just before sunset this evening. By 11, p.m., the leading star, Yed Prior or “the preceding star of the hand” is three fists held upright and at arm’s length above the southeast horizon.

Sunday: Tonight’s Moon is new. Don’t bother looking for it. The new moon is the phase where the Moon is directly between the Earth and the Sun. Hence the side of the Moon facing Earth is not receiving any sunlight and cannot be seen. This is why some people call this phase the “dark moon” and reserve the name “new moon” for the first visible waxing crescent after the Moon moves out from directly between the Earth and Sun.

Monday: Jupiter appears to have another Moon for the next few mornings. The planet Neptune is less than one pinky width to the upper left of Jupiter, the brightest point of light in that portion of the sky. They are two and a half fists above the south-southeast horizon at 11 p.m. Over the next couple of days, Neptune will move closer to Jupiter in the morning sky. Neptune is visible with binoculars.

Tuesday: U Scorpii is a recurrent nova that explodes about once every ten years. It gets over 2,000 times brighter for a few hours after the explosion. I wrote about it two weeks ago. Did you look for it? You will not be able to see it now without a 16 inch telescope. But once it explodes, you will be able to see it in binoculars. First find Antares one fist above the south-southeast horizon at 11 p.m. Then, looking through your binoculars, count up three stars that are of similar brightness yet much dimmer than Antares. U Scorpii will appear above this star when it explodes.

Wednesday: Saturn is four fists above the southeast horizon at 10 p-.m.

Thursday: Arcturus, the brightest star in Bootes the herdsman is six fists above due south at 11:30 p.m. The body of Bootes resembles a kite that spreads upward from Arcturus. Arcturus is most likely your wishing star – the first star you see tonight.

Friday: Cygnus the swan flies tonight. Deneb, the brightest star in the constellation, whose name means “tail” in Arabic, is two fists above the northeast horizon. Cygnus’ wings make a vertical line one half a fist to the right of Deneb. Its head, marked by the star Albireo, is two fists to the right of Deneb. While Deneb is at the tail of Cygnus, it is at the head of the line of bright stars. It is 160,000 times more luminous than the Sun making it one of the brightest stars in the galaxy. It does not dominate our night sky because it is 2,600 light years away, one of the farthest naked eye stars. If Deneb were 25 light years away, it would shine as bright as a crescent moon.

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

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