This is the Dudley Observatory Skywatch Line for Monday and Tuesday, January 30th and 31st written by Joe Slomka.
The Sun sets at 5:06 PM; night falls at 6:43. Dawn breaks at 5:33 AM and ends with sunrise at 7:10.
The three-day-old Moon, in Aquarius, dominates the southern sky at sunset. It shines at minus fifth magnitude and appears about 9 percent illuminated. Tuesday, it relocates to Pisces, shines two magnitudes brighter and lit about 16 percent. Tuesday finds the Moon in a tight, 5 degree, triangle with Venus and Mars – a sight to behold. The Moon sets at 8:10 PM on Monday, and at 9:17 PM on Tuesday.
Venus, the next brightest object lies 11 degrees to the Moon’s upper left on Monday. It sparkles at minus fourth magnitude, appears 40 percent illuminated and is 30 arc-seconds in size. Venus sets at 9 PM. Mars, the third part of the heavenly triangle, glows at first magnitude and appears a tiny 5 arc-seconds in size; it is about five degrees to Venus’ upper left. Mars’ distinctive red color makes identification easy. Mars sets at 9:26 PM.
Nightfall reveals three dimmer members of our Solar System. Neptune, in Aquarius, is 5 degrees to the Moon’s lower right. It is a dim eighth magnitude and a tiny 2 arc-seconds in size.
Neptune sets at 7:35 PM. Uranus is 19 degrees to Mars’ upper left in Pisces, is brighter at 5.8 magnitude and a bit larger at 3.5 arc-seconds. Uranus sets at 11 PM.
Minor Planet 4Vesta is currently in Gemini. The sixth magnitude asteroid is tiny, only 82 miles in diameter. Vesta is less than one degree from the star Al Kirkab, also called Kappa Geminorum. Vesta is best observed at about 11 PM and remains up most of the night. Observers wanting to see Neptune, Uranus or Vesta should use finder charts from astronomy sources.
Jupiter rises at about 11 PM in Virgo, above the bright star Spica. Observers can witness the moon Io’s shadow begin to cross Jupiter’s face at Midnight Tuesday, followed by Io itself at 1:10 AM; the shadow exits Jupiter at 2:12 AM, with Io exiting at 3:20 AM. The Great Red Spot is visible at 3:17 AM, Wednesday.
Saturn rises in Ophiuchus at 4:13 AM. It is bright at 0.5 magnitude and appears 15 arc-seconds in size. The rings are visible in binoculars and telescope before the sky becomes too bright.
Mercury is the last to rise, at 6:05 AM. It glows at minus 0.2 magnitude and is 80 percent illuminated. It can be located about 25 degrees to Saturn’s lower left, 5 degrees above the horizon.
Alvan Graham Clark, 155 years ago Monday night, was testing a newly made 18 and one-half inch refracting telescope. He trained it on Sirius. He saw a faint companion to the main star – the first known white dwarf star. Sirius B, as this companion is called, orbits the main star in about 50 years. It is far hotter than Sirius, slightly smaller than Earth, but nearly the Sun’s mass. Sirius B is actually a remnant of a far larger star that died, and is slowly cooling off.
The telescope that Alvan tested was installed at Northwestern University and is still in use.