This is the Skywatch Line for Monday and Tuesday, March 6th and 7th.
The Sun sets at 5:51 PM; night falls at 7:25. Dawn breaks at 4:47 AM and ends with the Sun rising at 6:21.
The Moon and two bright planets grace the darkening sky. The nine-day-old Moon rises about Noon on Monday in Gemini and blazes at minus 10th magnitude, appearing about two-thirds lit. Tuesday finds it slightly brighter and fatter. The Moon sets at 2:53 AM on Tuesday, and at 3:46 AM on Wednesday.
Three planets inhabit the moderately low western constellation of Pisces. Venus is next brightest at minus 4th magnitude, appearing large in our telescopes, but a slender 11 percent illuminated. This month, it dims slightly and its crescent thins to a hairline, but it appears slightly larger in our instruments. It sets at 8:20 PM. Mars, 17 degrees to Venus’ left, is next brightest at first magnitude and is easily identified by its red color. Mars sets about 9:22 PM.
Nightfall reveals Uranus, about 5 degrees to Mars’ lower right. This blue-green planet is much dimmer at sixth magnitude and appears tiny in telescopes; the observer should consult sky charts from astronomical media for a detailed location. Uranus sets at 8:53 PM.
Minor planet 4Vesta is also visible at twilight’s end. It shines at 7th magnitude, appears a tiny 0.4 arc-seconds, and lies about two degrees below the star Upsilon in Gemini. Again, detailed star charts help find it. It sets at 4 AM.
By 10 PM, Comet 45P appears above Leo’s back. Another challenge object, it is a dim 14th magnitude and a tiny size.
It is best observed at about 11:49 PM, again assisted by sky charts.
Jupiter rises in Virgo at 8:42 PM. It blazes at minus 2nd magnitude, above the 1st magnitude star Spica. This month Jupiter begins a retrograde (westward) trek; it also brightens and enlarges slightly. At 1:02 AM on Tuesday, the telescopic observer can witness the moon Europa disappear behind Jupiter and reappear at 4:52 AM. Jupiter is best observed at 2:17 AM.
Finally, Saturn rises in Sagittarius at 2:06 AM. It shines at zero magnitude and is moderately large in our telescopes. By Dawn, it is high enough to enjoy views of its beautiful rings.
Since Jupiter and Saturn are visible simultaneously, comparisons are in order. Both are gas giants – planets composed mostly of gas. Jupiter is larger; Saturn is about a third of Jupiter’s mass. In telescopes, Jupiter’s colored bands signify active weather systems; one storm, the Great Red Spot, has been continuously observed for centuries. Saturn’s weather appears more subdued, with occasional faint features. Saturn’s ring system is easily visible from Earth. Jupiter’s rings are observable only from space-borne telescopes. Both planets’ 120 moons account for most of the Solar System’s total. Four of Jupiter’s moons appear in binoculars, while Saturn’s satellites can only be spotted through a telescope. Jupiter’s moon Io is the most volcanically active moon in the Solar System, while Europa, Ganymede and Callisto may conceal oceans beneath their icy surfaces. Saturn’s moons Enceladus and Titan are geologically active, which spurt ice fountains. Titan is the only moon to have an atmosphere; however, its atmosphere contains cold methane, rather than oxygen. Titan also has vast lakes of liquid methane on its surface.