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Lunar corona

Photo of the Week.A lovely "diffraction corona," caused by the interference among light waves as they pass through light clouds, surrounds the waxing crescent Moon.

Astronomy news for the week starting Friday, January 2, 2015.

Yay, we are back to weekly, at least for a time, and best wishes for the coming year.

The week gloriously centers on the full Moon, which takes place around midnight Sunday, January 4, with the Moon high in the sky. Before that, it waxes in its gibbous phase while after it gibbously wanes. A telescopic view of the full Moon is often disappointing, as the craters seem to disappear as the shadows that highlight them are hidden. But the lunar "rays" brilliantly stand out. Centered on young craters, the rays are strings of secondary craters caused by violent impacts. The Moon passes apogee , where it is farthest from Earth, on Friday, January 9. The night of Thursday the 8th, the Moon passes five degrees south of Jupiter (about the separation of the front bowl stars of the Big Dipper), closest approach taking place around 2 AM CST, midnight on the west coast. The near-full Moon will ruin the normally-good Quadrantid meteor shower, which emanates from the defunct constellation Quadrans (the Quadrant) near the Big Dipper and peaks the mornings of January 3 and 4.

The giant planet rises just before 8 PM to the west of the star Regulus in Leo. Before that, if you have a clear western horizon, you might spot brilliant Venus, which sets shortly before the end of evening twilight. It's playing games with Mercury, the two no more than a degree apart the last part of the week, Venus the brighter of the pair. Fading (though still first magnitude) Mars faithfully sets at 8 PM (as Jupiter rises), which it will do through the winter and early spring as it climbs slowly to the north, this week in eastern Capricornus.

The biggest planetary event is of Earth, which passes perihelion, its closest point to the Sun, around midnight the night of Saturday the 3rd, when it will be 1.47096 million kilometers (91.40 million miles) from the Sun, 0.983 times average. That perihelion occurs during the coldest time of the northern year shows that distance from the Sun has little to do with the seasons, which are caused by the tilt of the Earth's rotational axis relative to its orbital axis.

In mid-evening, Perseus, the hero of the Andromeda myth, is in full glory, shining down from nearly overhead, its fainter stars unfortunately washed out by the bright Moon. To the northwest of him shines W-shaped Cassiopeia, to the east the Pentagon of Auriga with bright Capella. South of Auriga, Orion climbs the eastern sky, Taurus in between.

One of the better and more interesting meteor showers, the Geminids, peaks the morning of Saturday the 14th. Capable of more than a meteor a minute, the shower will be marred by a quarter Moon. The Geminids are the debris of Comet 3200 Phaeton. Once thought to be an asteroid, Phaeton orbits the Sun in a short period of just 1.43 years and comes well inside the orbit of the Earth (but does not intersect us).

Right in the middle of things, in early evening find the Great Square of Pegasus high to the south, Andromeda streaming off its upper left corner. Then around midnight climbs one of the great glories of the sky, Orion, the Hunter, with his silvery three-star belt and the magnificent red supergiant Betelgeuse at the upper left. Wait a bit then to see the rising of brilliant Sirius, the brightest star of the sky.

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