Friday, May 9
As twilight fades this evening, there's a lot going on across the
western side of the sky. The Moon hangs just below the lengthening line
of Mars, Pollux, and Castor, as shown at right. Down to their lower left
shines Procyon. Farther to their lower right twinkles Capella (out of
the frame). And the Saturn-Regulus pair poses high off to the upper
left.
And there's more going on lower down! Between 8 and 9 p.m. daylight
saving time (depending where you live in your time zone), viewers at
mid-northern latitudes can see Mercury at exactly the same altitude in
the west-northwest as Vega is on the other side of the sky in the
northeast — on the night they're exactly the same magnitude, 0.0. Clear,
unobstructed horizons are important, as both will be less than about 9°
high. (Thanks to David Likuski for spotting this event.)
The Moon, nearly first quarter now, forms a long arc with Mars,
Pollux, and Castor, as shown above. Seen from eastern North America this
evening, the Moon skims the edge of the Beehive star cluster (M44); use
binoculars or a telescope at low power.
First-quarter Moon (exact at 11:47 p.m. Eastern Daylight Time).
Saturn and Regulus shine to the right of the Moon this evening, as
shown here.
Face southeast after dark and look very high for bright Arcturus, 37
light-years away. Look low in the northeast for equally bright Vega, 25
light-years away. These are the two brightest stars of late spring and
summer. Their nearness has a lot to do with this; stars visible to the
unaided eye are typically 100 to more than 1,000 light-years distant.
Look a third of the way from Arcturus to Vega for the dim little
semicircle of Corona Borealis, the Northern Crown. It's highlighted by
one modestly bright star, Gemma or Alphecca, magnitude 2.2.
A small telescope will always show Titan, Saturn's largest and
wildest moon. Tonight through Saturday, Titan is three or four
ring-lengths to Saturn's west. A 6-inch telescope will begin to show the
orange color of its smoggy atmosphere. A guide to identifying all six of
Saturn's satellites that are sometimes visible in amateur scopes is in
the May
Sky & Telescope, page 60.
Look above the waxing gibbous Moon this evening for the hot star
Spica, pale blue-white. Arcturus is far off to their upper left.
How low can you see to your north horizon? That's where you'll find
W-shaped Cassiopeia around 10 or 11 p.m. this week. If you're far
enough north, that is! From the latitudes of Atlanta, Houston, and San
Diego, part of the Cassiopeia W will be below the horizon. From South
Florida, the W goes below the north horizon completely.
Saturday, May 10
Sunday, May 11
Monday, May 12
Tuesday, May 13
Wednesday, May 14
Then look two thirds of the way from Arcturus to Vega for the Keystone of Hercules, highlighted by nothing at all.
Thursday, May 15
Friday, May 16
Saturday, May 17