Skylights featured on Astronomy Picture of the Day

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Skylights featured three times on Earth Science Picture of the Day: 1 , 2 , 3 , 4 .

W Orionis

Photo of the Week.. The carbon star W Orionis stares redly back at us from the middle of the picture. Orion's Bellatrix is at upper left, while the right hand star of the belt shines at lower left.

Astronomy news for 9 days starting Friday, February 27, 2004.

Skylights will next appear on Sunday, March 7.

The Moon waxes through its gibbous phase during this extended period, beginning with first quarter on Friday, February 27 (during mid evening in North America), and ending with full on Saturday, March 6 (just before moonrise). The evening of Monday the 1st, the Moon will be seen to the north of Saturn, while on the nights of Friday the 5th and Saturday the 6th it will bracket much brighter Jupiter.

This week, on the night of Wednesday March 3rd, Jupiter passes opposition with the Sun, when it rises at sunset, sets at sunrise, crosses the meridian to the south at midnight (roughly when formal opposition is actually taking place), and is in the middle of its retrograde, or backward, motion. About two hours after sundown, around 8 PM, Saturn crosses the meridian. Then only three hours before Jupiter comes into formal solar opposition, Mercury passes its superior conjunction with the Sun, when it is on the other side of the Sun from us and completely invisible. Meanwhile, Mars and brilliant Venus hang out in the western sky drawing ever closer, Venus now setting around 9:30, Mars two hours later, the early evening sky now containing all the ancient planets but Mercury.

As a special treat, the week gives us February 29, this "leap year" occurring only once every four years. The purpose is to reconcile the days in the calendar to the actual length of the year, which is close to 365 and a quarter days long. Over a four year period, the calendar therefore averages 365.25 days. The problem is that the actual number of days in the year is 365.2422..., so given this simple system (of the original Julian calendar, after Julius Caesar), the dates of the equinoxes and solstices creep forward. This problem is solved in our Gregorian calendar (after Pope Gregory XIII of the late 16th century) by dropping leap years in century years not divisible by 400. Thus 1900 (which falls on the four year cycle), was not a leap year, 2000 was, and 2100 will not be. The result is a 400 year average of 365.2425 days, very close to reality.

What dominates the early evening sky now more than anything else is Orion (which is starting to slip a bit west) and his two hunting dogs, Canis Major (the Larger Dog, with Sirius, the brightest star of the sky) and Canis Minor (the Smaller Dog, with Procyon). With Orion's reddish Betelgeuse, these two stars make the prominent "Winter Triangle," Procyon east of Betelgeuse, Sirius to the southeast. Due west of Sirius is the box-like set of stars that make Lepus, the Hare, while directly below Lepus find the flat triangle that forms Columba, the Dove.
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