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30 Jan 2015
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Two planets and a star far outshine all competitors at dusk in February. They are: Venus, of magnitude -4, low in the west-southwest, shifting toward the west and slowly gaining altitude as this month progresses; Jupiter, of magnitude -2.6, starting very low in the east-northeast, moving into the east and climbing about 1 degree higher each day (if viewed at the same stage of twilight daily); and blue-white Sirius, the “Dog Star” and brightest of nighttime stars, twinkling at magnitude -1.4 and ascending through southeast toward south-southeast at dusk as February runs its course. Follow these three bright objects at dusk in coming months. Sirius will disappear into the west-southwest twilight glow during May, while Venus and Jupiter remain in view until at least late in July. February’s other naked-eye evening planet is Mars, appearing as a red “star” of magnitude +1.2 to +1.3, not far from Venus all this…
02 Jan 2015
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The year begins with the three other terrestrial (rocky) planets of our solar system—Mercury, Venus and Mars—low in the west-southwest to southwest during evening twilight. Their span shrinks from 27 degrees on Jan. 1, to less than 20 degrees Jan. 11-20. Bright Venus, of magnitude -3.9, draws attention to the gathering. Find Mercury just to its lower right, within 3 degrees Jan. 1-17, 2 degrees Jan. 4-15, and 1 degree Jan. 8-12. On Jan. 10 at dusk, Mercury appears within two-thirds of a degree to the lower right of Venus! As seen from Earth, Mercury will not overtake Venus, and will instead fall just short. This is a quasi-conjunction, an approach within 5 degrees without an actual conjunction, when two planets share the same “x-coordinate.” Mercury shines at magnitude -0.8 Jan. 1-11, fades through magnitude 0 on Jan. 19, magnitude +1 on Jan. 22, and magnitude +2 on Jan. 24,…
30 Nov 2014
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Near the start of December every year, the first-magnitude star Aldebaran, eye of Taurus the Bull, and “follower” of the Pleiades, or Seven Sisters, is visible all night as Earth makes its annual passage between Aldebaran and the sun. Look for Aldebaran low in the east-northeast at dusk, high in the south in the middle of the night, and low in the west-northwest at dawn. On New Year’s Eve, the brightest star, Sirius the Dog Star, reaches its high point in the south in the middle of the night. You can observe Sirius for much of that night, but not at dusk or dawn, because the star’s path from rising to setting is too far south and too short to keep it above the horizon through the long winter night. Some 21 to 22 minutes earlier, and 36 degrees lower than Sirius at its highest, observers in Southern California can…