Skywatch Line for Friday, January 31, through Sunday, February 2, written by Sam Salem
This is Dudley Observatory’s Skywatch Line for Friday, January 31, through Sunday, February 2, written by Sam Salem.
On Friday, Sun rises at 7:11am and sets at 5:07pm; Moon rises at 8:33am and sets at 7:51pm.
The waxing crescent Moon lines up with Saturn and Venus on consecutive evenings. On Friday, the Moon and Saturn are 3° apart, then on Saturday, the brilliant Moon-Venus pair are just 2½° apart.
On Sunday, the growing waxing crescent Moon will lie above Venus and Saturn in the western evening sky. Saturn will be edging closer to the horizon all month and slip away by month’s end.
The Moon will reach perigee, its closest point to us in its elliptical orbit around Earth, on Sunday when it’s 228,327 miles away.
Venus, magnitude –4.8 near the dim Circlet of Pisces, shines high and bright as the “Evening Star” in the southwest during twilight, then lower in the west-southwest as evening grows late. It sets almost due west nearly 2½ hours after dark. In a telescope this week Venus appears about 40% sunlit: a thick crescent.
Increasingly far below Venus is fainter Saturn. Saturn, magnitude +1.1 in Aquarius, is a little spark below brilliant Venus during and after dark.
Mars was at opposition on January 15th. It’s now shrinking and fading a bit, to about 14.0 arcseconds in diameter and magnitude –1.1. Mars comes into view in twilight as a steady orange spark low in the east-northeast. As darkness deepens, watch for Pollux and Castor emerge into view upper left of it. Mars climbs high into good telescopic viewing earlier now. It’s best examined from mid-evening through midnight, when it’s high in the southeast to south.
Jupiter, nearly two months past opposition, shines at a bright magnitude –2.5 in Taurus. It dominates the high south in early evening, near Aldebaran and the Pleiades. Jupiter is still 44 arcseconds wide.
On Saturday, Jupiter’s moon Io enters onto Jupiter’s face at 6:41 p.m. coming from the east, then it exits from Jupiter’s western limb at 8:53 p.m.
Following behind Io across the planet’s face, from 7:50 to 10:02 p.m., will be Io’s tiny black dot of a shadow.
The biggest well-known asterism, the Winter Hexagon, fills the sky toward the east and south these evenings. Start with brilliant Sirius at its bottom. Going clockwise from there, march up through Procyon, Pollux and Castor, Menkalinan and Capella on high, down to Aldebaran, then to Rigel in Orion’s foot, and back to Sirius. Betelgeuse shines inside the Hexagon, way off center. If you draw a line through its middle from Capella down to Sirius, the “Hexagon” is symmetric with respect to that long axis. Take the line
from Aldebaran to Capella, turn it to go from Aldebaran to Betelgeuse, and the Winter Hexagon becomes a giant letter G.