Astronomy news for the week starting Friday, April 22,
2011.
The beginning of our new week sees the Moon in its waning
gibbous phase as it prepares to pass third
quarter on Sunday, April 24, shortly before Moonrise in North
America. It then spends the remainder of our period as a waning
crescent that will not reach new Moon until the night of May
2nd. The morning of Friday the 29th will find the Moon beginning
a visit with Venus, when the planet will be well down and to the left of
the narrowing crescent. The crescent will also pass well to the
north of Neptune on Wednesday the 27th and then do the same with Uranus the night of Friday the 29th, the events of no real
consequence. We then end the week with the Moon a day shy of apogee, where
and when it is farthest from Earth in its monthly round.
With Venus sinking into morning twilight (the planet not rising
until half an hour after the sky begins to brighten), with
Mars and
Jupiter yet to emerge from it, and with Mercury stashed within dawn's light (down and to the left
of Venus) as well, we are left to admire Saturn
, which is on beautiful display. Rising well before sunset, it
is nicely up in the east by the time the sky darkens, crosses the
meridian to the south around 11:30
Daylight time, and does not set until after the onset of dawn.
Being so far from the Sun, nearly 10 times farther than Earth, it moves so slowly
against the stellar background that it maintains its position
within a given constellation of
residence for a long time, as witnessed by its continuing proximity
to Spica, which has been lying to
the southeast of the planet for some time, the two making a fine
sight as they cross the nighttime sky. Even a small telescope will
give a good view of the rings, which are by
far the brightest such structures in the Solar System. Their
origins long unclear, they are now thought to have been caused by
the tidal destruction of an icy satellite.
To the north and a bit to the west of Saturn and Spica rises one of
the most glorious stars of the sky, Arcturus. Brightest of the
northern hemisphere, and fourth brightest in the heavens (after
southern Sirius, Canopus, and Alpha Centauri, the latter two invisible from all
but the deep southern parts of the US), it is quite recognizable
south of the handle of the Big
Dipper by its orangish color. Look then for the rest of its
constellation, Bootes, the
Herdsman. Stretching out to to north-northwest of Arcturus like a
giant kite, Bootes drives the Great
Bear (of which the Dipper is a part) around the pole.
