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The Sky This Week, 2011 February 8 - 15

Longer days, bright Moon and bright stars.

 Jupiter, 2011 FEB 6, 23:56 UT

The Moon brightens the evening sky as she climbs resolutely toward the wintertime constellations. First Quarter occurs on the 11th at 2:18 am Eastern Standard Time. Look for Luna just south of the Pleiades star cluster on the evening of the 11th. Two nights later she stands high above the figure of Orion, close to the star that marks the southern horn of Taurus, the Bull. By the end of the week she is wending her way among the stars of Gemini.

If you are one to believe in popular folklore, the fact that the groundhog did not see his shadow last week gives us hope for an early spring. While the astronomical season is still some six weeks in the future, there are signs that we’re coming out of the year’s darkest days in the air right now. By the end of the week the Sun sets a full hour after its earliest setting back in December, and sunrise now occurs almost half an hour earlier than it did a month ago. On average we’re now adding just over two minutes of daylight to the total length of day with each diurnal cycle. This rate will continue to gradually increase as we move close to the equinox, at which time the length of day will be about 18 minutes per week. It’s the time of year when I really notice the change. Somehow watching the days grow shorter isn’t as pleasant as watching them grow longer!

The waxing Moon washes out all but the brightest of winter’s stars as the week progresses, but fortunately these stars are withstand Luna’s photon onslaught and shine down to delight our eyes. The unmistakable figure of Orion straddles the meridian at around 8:30 pm, anchoring the stars of the Great Winter Circle surrounding him. Begin your clockwise tour of these stars with Sirius, the brightest star in the sky, which lies below and to the left of the Hunter. From there proceed up to Procyon, then past Castor and Pollux, the Twin Stars of Gemini. Continue your sweep over Orion to the golden-hued star Capella, then circle down past the eye of Taurus represented by the ruddy hued Aldebaran. From there move down to bluish Rigel on Orion’s knee. This large circle contains nine of the 25 brightest stars in the sky, so it stands out even under the light of the Full Moon.

Giant Jupiter is still drawing our attention in the western sky as evening twilight deepens, but his time of prominence is rapidly drawing to a close. Old Jove is only 30 degrees above the horizon 45 minutes after sunset, and this elevation is generally considered the limit for useful telescopic observation. Atmospheric extinction, refraction, and turbulence now render his disc into a color-fringed undulating blob of light, and only nights of exceptionally still air will allow much detail to be seen on his surface. His four bright Galilean moons remain visible, though, and you can watch their antics for a few more weeks before the Sun’s twilight glare overwhelms them.

Saturn now rises at around 10:00 pm along with the stars of spring. You can train the telescope on him by midnight and expect to see a fine view of his widening rings. If you’re out at the right time you may also be able to see a whitish streak on the northern face of his disc. This is the plume from a giant storm that erupted on the ringed planet several weeks ago. It continues to be active, so it should be visible for several more weeks.

Dazzling Venus takes a little work to track down in the pre-dawn sky. She’s currently at her most southerly declination, so she’s quite close to the southeast horizon. The best time to look for her is in the hour before sunrise.

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