Astronomy news for the week starting Friday, February 26, 2010.
Our perpetual Moon, which has
rounded the Earth for some 4.5 billion years, passes through yet
another full phase this week, on Sunday,
February 28, during daylight in North America. It will thus rise
just short of full the evening of Saturday the 27th, and just a bit
beyond that phase the following night. So we get to see a couple
days of the waxing gibbous, and then a
long run the rest of the week of the waning
gibbous phase, third quarter not
achieved until Sunday the 7th.
The nights of Friday the 26th and Saturday the 27th find the Moon
passing south of the Sickle of Leo, while the night of Monday, March
1 (more the morning of Tuesday the 2nd), look for the Moon to be
eight or so degrees south of Saturn
. A day before full, the Moon passes perigee,
where it is closest to Earth. Watch out for high tides. Though
not in the midwest.
It's time to celebrate
Jupiter, though by its absence, as it finally passes
conjunction with the Sun at the end of our
short month, on Sunday the 28th. The giant planet, which is not so
much a gas giant but a ball of liquid molecular hydrogen, will
thereafter appear in the morning sky, though it will not be visible
in twilight until April warms the ground.
As for large planets, then, Saturn will have to serve. And it and
its ring system do so beautifully, the planet now rising just after
the end of evening twilight, still in Virgo just 3.5 degrees east of the Autumnal Equinox (and in
retrograde, slowly closing in on it). Retrograde, westerly,
planetary motion was of course the original clue that the planets
go around the Sun (rather than Earth), as this backward motion
occurs as we pass them (or they pass us) in orbit. Saturn then
crosses the meridian to the south
around 1:30 AM and is still in the sky, to the east, at
dawn.
But never mind so much Saturn, about keep your eye out for Venus
, which now rises in mid-twilight, and thanks to a high tilt of
the ecliptic is becoming ever
more visible. Once seen, it will be with us most of the year, not
crashing through twilight again until September, creating for us a
glorious summer sight.
That leaves Mars. Though
still bright, it is noticeably fading as it transits the meridian
ever earlier, now around 9:30 PM, the planet setting about as
twilight lights the morning sky. It's in a fine setting between Gemini's Castor and Pollux pair and Cancer's Beehive
Cluster.
If there is a season for Sirius,
the luminary of Canis Major (the
Larger Dog), this is it. At least in early evenings, when the star
shines brightly to the south. One of the closest stars to Earth,
only 8.6 light years away, it is famed for its twinkling sparkle,
the result of variable refraction and dispersion in the Earth's
atmosphere. It's even better known for its companion, a shrunken
white dwarf about
the size of Earth that was at one time by far the more magnificent
of the two.
