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.
