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Sirius and Canopus

Photo of the Week. As seen from an Atlantic Ocean beach, Canis Major's Sirius, the sky's brightest star, rides high above number two Canopus, the luminary of Carina in Argo. (The Star of the Week, Chi Carinae, is very faintly visible directly to the left of Canopus; bright Regor [Gamma Velorum] is up and farther left.)

Astronomy news for the week starting Friday, April 11, 2008.

The Moon starts off the week nearly at first quarter, the actual phase reached on Saturday, April 12, about the time of Moonrise in North America. It then waxes in the gibbous as it heads towards full phase next week, on Sunday the 20th.

Our companion than takes on a pair of planets and a star. The night of Friday the 11th, the Moon will make a fine pairing with Mars, passing less than a degree to the north of the red planet. The Moon will actually occult Mars as seen from northeastern Canada, Greenland, Iceland and other points far north. Next up is Regulus, which the Moon passes to the south of during the day on Tuesday the 15th. Four hours later the Moon then passes to the south of Saturn. The Moon will therefore be to the west of the star and planet the night of Monday the 14th, then to the east of them the following evening.

Only half again as far from the Sun as Earth, Mars falls only slowly behind us, which will keep the planet in the evening sky until next autumn, the setting time (now around 2:30 AM Daylight Time) not changing much from one night, or even week, to the next. As the sky darkens, find Mars high in the west in central Gemini to the southwest of Castor and Pollux. We now, however, see something of a transition, as at mid-northern latitudes, Mars sets in the northwest just as Jupiter rises in the southeast, the giant planet then dominating the sky until bright dawn takes it away. As witnessed by the above lunar passages, Saturn remains securely in Leo to the east of Regulus. The ringed planet can be found high to the south, transiting just after the end of evening twilight, and not setting until nearly the commencement of dawn. As a bit of a coda to the planetary sky, Mercury passes the Sun in superior conjunction (the other side of the Sun) on Wednesday the 16th as it prepares for a rather nice appearance in mid-May.

Almost due south of Canis Major's Sirius, Canopus, the sky's second brightest star, is visible only from the southern US and points south. It's the luminary of Carina, the keel of the Ship of the Argonauts, which extends to within 20 degrees of the South Celestial Pole and which contains one of the most massive stars of the Galaxy, Eta Carinae. Between Canopus and Sirius lie the stars of Puppis, the Stern of the Ship, which wraps up and to the east around the Great Dog. If you are too far north to see Canopus, you might imagine it gliding across the southern horizon.
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