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The Sky This Week, 2017 February 21 - 28

Count some stars, then cozy up to Venus.
Venus_12_170206_01.jpg

Venus, imaged 2017 February 6 with USNO's 30.5-cm (12-inch) f/15
Clark/Saegmüller refractor,

a 1.6X Antares Barlow lens and a Canon EOS Rebel T2i DSLR


The Moon is notable for her near-absence from the sky this week. New Moon occurs on the 26th ay 9:58 am Eastern Standard Time. You might catch a glimpse of her waning crescent phases in the pre-dawn sky early in the week. She should re-appear in evening twilight on the evening of the 27th. On the following evening she sees February out the door in an attractive grouping with dazzling Venus and ruddy Mars.

You have another opportunity to participate in the Globe at Night citizen-science program this week by counting the number of stars you can see in the vicinity of the familiar outline of Orion, the Hunter. He crosses the meridian just before 8:00 pm, so you should have a good view of him under darkness at that time. To participate in the program, go to the website and compare your view of Orion with the various charts that show his appearance under different sky conditions, then enter your report. There are free apps you can get for your smart phone that you can use to report directly from the field. Submit as many reports as you desire, preferably from different locations. You’ll help scientists determine the spread of urban light pollution and map out dark-sky sites for skywatchers to use.

Despite what the groundhog indicated a few weeks ago, the signs of spring are definitely in the air in the Washington, DC area. One sure way to see this is the rapidly lengthening change in the length of day. By the end of the week sunset occurs at 6:00 pm EST and the length of day increases by about three minutes per day. By the end of February we’ll have just under two hours’ more daylight than we did at the winter solstice. In just three more weeks we’ll have the official vernal equinox, so enjoy the last few weeks of early evening darkness.

Once Orion slips west of the meridian, followed by the eastern stars of the Great Winter Circle, the stars of spring begin to take over the sky. By midnight the signature constellations of spring are approaching their apexes. To the north you’ll find the seven stars of the Big Dipper asterism, and just south of the zenith look for the bright star Regulus, the heart of Leo, the Lion. The deep-sky objects shift from galactic star clusters and nebulae to external galaxies as our gaze is directed above and out of the plane of the Milky Way galaxy. Several of these remote star cities are visible in small telescopes, and binoculars at a dark sky site will show Messier 81 and 82, one of the closer galaxy groups to our vast spiral home.

Venus continues to dazzle in the western sky during twilight and for over an hour in full darkness. She is now turning northward away from ruddy Mars, and over the course of the week the gap between them widens by nearly four degrees. A small telescope will easily show her crescent phase, which narrows a bit each day as she begins her plunge toward the Sun.

Mars manages to continue to keep pace with the Sun, setting each night at around 9:30 pm. His telescopic disc has now shrunk to miniscule proportions, just under five arcseconds across. You’ll need a large telescope and steady air to see any detail on his distant surface.

Jupiter now rises four minutes earlier with each passing night, and by the end of the month comes up at around 9:20 pm. He’s well up in the southeast by midnight. Look just a few degrees below Old Jove for the bright blue star Spica.

Saturn is now best seen in morning twilight, far to the south among the rising stars of Sagittarius. The ringed planet will be at his best during the summer months this year, but if you’re up before the sun he offers a pleasant view of his wide-open rings right now.

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