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The Sky This Week, 2017 March 21 - 28

Count stars in March's Lion.
Orion and Canis Major, imaged 2017 March 2,
from Flagstaff Mountain Road, Boulder, CO,
with a Canon EOS Rebel T2i DSLR

The Moon is inconspicuous for most of the week, best seen as a thin waning crescent in the pre-dawn southeastern sky. New Moon occurs on the 27th at 10:57 pm Eastern Daylight Time. You’ll find Luna among the faint stars of the rising autumnal constellations. She will re-appear inn the evening sky by the middle of next week.

Take advantage of the Moon’s absence this week to participate in the March campaign for the Globe at Night citizen-science program. This month we’re asking people to look for the constellation of Leo, the Lion, which is well-placed in the eastern sky by 10:00 pm. There are two asterisms that make up the constellation. The brighter part consists of the first-magnitude star Regulus, which can be seen as the period under a "backwards" question mark made up of second- and third-magnitude stars. Known popularly as "The Sickle", it represents the Lion’s head, with Regulus marking his heart. The second asterism consists of a right triangle of two second- and one third-magnitude star. Most of these stars should be visible from a suburban yard away from direct lighting. There are many fainter stars as well, and your job is to see how faint a star you can see. You can record your findings on the Globe at Night website and help scientists measure the effects of outdoor lighting and air pollution.

You can still spend some quality time with the bright constellation Orion and his cohorts earlier in the evening. At the end of evening twilight the Hunter is well west of the meridian, closely followed by his faithful dog Canis Major. The bright blue star shimmering near the Dog’s "head" is Sirius, the brightest star in the nighttime sky.

Venus officially passes inferior conjunction, the moment when she passes between the Earth and the Sun, on the 25th at 6:17 am. The dazzling planet will quickly move into the morning sky, becoming visible in the twilight glow by the end of the month.

In the meantime, the fleet planet Mercury is undergoing his best evening apparition for the year. You should be able to locate him in binoculars, where you can find him about 10 degrees above the western horizon half an hour after sunset. The slim waxing crescent Moon should help you find him on the 29th, when the elusive planet lies about 10 degrees to the right of Luna.

Mars is also visited by the Moon on the evening of the 30th. The red planet will lie about seven degrees to the right of the Moon’s crescent. Mars continues his trek across the stars of Aries, drawing a bead on the brighter stars of nearby Taurus.

Jupiter is fast approaching opposition, and the giant planet now rises at around 8:30 pm. He’s well up in the southeast by 11:00 pm, and you may wish to take a look at him before retiring for the evening. On the evening of the 26th you can see the Great Red Spot rotate across the planet’s cloud-streaked disc. At the same time the shadow of the moon Io will also cross the planet’s face.

Saturn is still best seen in the pre-dawn sky. You’ll find the ringed planet near the meridian at 6:00 am EDT.

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