Astronomy news for the week starting Friday, February 24, 2012.
We can spend the early part of the week admiring the waxing crescent Moon, at least until the
night of Wednesday, February 29 (that's right, 29th, don't forget),
when we get the first quarter high in
North American skies. We then see a couple days of the waxing gibbous, full phase not reached until late
next week.
This week we get to see some fine pairings, but only in early
evening western skies. The night of Friday, February 24, the Moon
will make a beautiful partnering with Venus, the planet up and to the left of the
crescent. The following night, that of Saturday the 25th, the
Moon will be only three or so degrees up from our brilliant
neighbor, with Jupiter up and
to the left of the pair. Then the next night, that of Sunday the
26th, the crescent Moon similarly takes on Jupiter, the Moon just
a few degrees to the right, Venus now below. Then keep watching.
The night of Monday the 27th finds the Moon, Jupiter, and Venus in
a ragged descending line. Our Moon then visits with the Pleiades of Taurus the evening of Tuesday the 28th (the cluster to the right) then
with the Hyades and Aldebaran, which will lie below and
a bit left of the quarter Moon the night of Wednesday the 29th
(there it is again).
Ignoring the Moon, Jupiter and Venus (the lower and by far the
brighter of the pair) dominate early evening western skies. With
Venus moving east of the Sun, Jupiter toward it (the two drawing
together), the difference in setting times is diminishing, Venus
now setting around 9:30, Jupiter just an hour later. The night of
Thursday, March 1, the two point downward toward Mercury, which
in twilight will be hovering just above the horizon. On the other
side of the sky, in the east
Mars is already well up (still in southeastern Leo) as twilight ends, with Saturn following well
behind, rising around 10 PM still with Spica to the southwest of it. Mars
then culminates the meridian to the
south not long past midnight, Saturn around 3:30 AM.
The leap year was invented in 46 BC under Julius Caesar, whose
astronomer Sosigenes added a day every four years (now our February
29) to make the average length of the calendar year 365.25 days,
very close to the true value of 365.2422...days. Good but not
perfect. In the 16th Century, Pope Gregory XIII ordered (on advice
from his astronomers) leap years to be dropped in century years not
divisible by 400, making for an average over 400 years of 365.2425
days, almost perfect, allowing the calendar to stay in close
synchrony with the seasons.
And though they are slipping away, the constellations of winter still ride
the early evening skies, Orion
and his two Dogs (Canis Minor with
Procyon, Canis Major with Sirius) parading through the south
and west, Sirius crossing the meridian around 7:30 PM. Look
directly above it to find Gemini
with Castor and Pollux forever (so far as we are
concerned) together, dim Cancer and
then Leo with Mars to the east, Leo, now holding Mars, a welcome
harbinger of spring.
