Skylights featured on Astronomy Picture of the Day

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Skylights featured nine times on Earth Science Picture of the Day: 1 2 3 4 5 6 7 8 9 -- Full List Restored!


Photo of the Week. Reflections (Bruce Kaler).

Astronomy news for the week starting Friday, February 24, 2012.

We can spend the early part of the week admiring the waxing crescent Moon, at least until the night of Wednesday, February 29 (that's right, 29th, don't forget), when we get the first quarter high in North American skies. We then see a couple days of the waxing gibbous, full phase not reached until late next week.

This week we get to see some fine pairings, but only in early evening western skies. The night of Friday, February 24, the Moon will make a beautiful partnering with Venus, the planet up and to the left of the crescent. The following night, that of Saturday the 25th, the Moon will be only three or so degrees up from our brilliant neighbor, with Jupiter up and to the left of the pair. Then the next night, that of Sunday the 26th, the crescent Moon similarly takes on Jupiter, the Moon just a few degrees to the right, Venus now below. Then keep watching. The night of Monday the 27th finds the Moon, Jupiter, and Venus in a ragged descending line. Our Moon then visits with the Pleiades of Taurus the evening of Tuesday the 28th (the cluster to the right) then with the Hyades and Aldebaran, which will lie below and a bit left of the quarter Moon the night of Wednesday the 29th (there it is again).

Ignoring the Moon, Jupiter and Venus (the lower and by far the brighter of the pair) dominate early evening western skies. With Venus moving east of the Sun, Jupiter toward it (the two drawing together), the difference in setting times is diminishing, Venus now setting around 9:30, Jupiter just an hour later. The night of Thursday, March 1, the two point downward toward Mercury, which in twilight will be hovering just above the horizon. On the other side of the sky, in the east Mars is already well up (still in southeastern Leo) as twilight ends, with Saturn following well behind, rising around 10 PM still with Spica to the southwest of it. Mars then culminates the meridian to the south not long past midnight, Saturn around 3:30 AM.

The leap year was invented in 46 BC under Julius Caesar, whose astronomer Sosigenes added a day every four years (now our February 29) to make the average length of the calendar year 365.25 days, very close to the true value of 365.2422...days. Good but not perfect. In the 16th Century, Pope Gregory XIII ordered (on advice from his astronomers) leap years to be dropped in century years not divisible by 400, making for an average over 400 years of 365.2425 days, almost perfect, allowing the calendar to stay in close synchrony with the seasons.

And though they are slipping away, the constellations of winter still ride the early evening skies, Orion and his two Dogs (Canis Minor with Procyon, Canis Major with Sirius) parading through the south and west, Sirius crossing the meridian around 7:30 PM. Look directly above it to find Gemini with Castor and Pollux forever (so far as we are concerned) together, dim Cancer and then Leo with Mars to the east, Leo, now holding Mars, a welcome harbinger of spring.
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