Skywatch Line for Friday, March 6, through Sunday, March 8, written by Sam Salem
This is Dudley Observatory’s Skywatch Line for Friday, March 6, through Sunday, March 8, written by Sam Salem.
On Friday, Sun rises at 6:23am and sets at 5:51pm; Moon sets at 7:28am and rises at 9:37pm. Daylight-saving time begins at 2:00 am Sunday morning. Clocks “spring ahead” one hour.
Late on Friday evening, the waning gibbous Moon will be near Spica, the brightest star in Virgo the Maiden. You can also catch them before dawn.
On Sunday morning, the waning gibbous Moon will be near Zubenelgenubi, the brightest star in the constellation of Libra the Scales. Then on Monday morning, the Moon will be near the red star Antares, the brightest star in the constellation of Scorpius the Scorpion. Try to spot 3 moderately bright stars known as the Crown of Scorpius. They are positioned above Antares, sometimes referred to as the “forehead” of the scorpion.
In March, look after dusk for the zodiacal light. It looks like a faintly glowing pyramid on the horizon, and it appears when all traces of twilight have left the evening sky. The zodiacal light is visible in dark skies during the months around the equinoxes. Look for it when the Moon isn’t out or is only a slender crescent.
Mercury reaches inferior conjunction, when is passes between Earth and the Sun, on Saturday. Mercury will emerge in the morning sky this month on its way to its greatest distance from the morning Sun on April 3.
Venus and Saturn pair up the first week of March. They’ll be closest to each other on Saturday and Sunday evenings. Look for them in the bright western twilight shortly after sunset. After Sunday, Saturn will soon be lost in the Sun’s glare and slip out of the evening sky.
On Friday, beginning at midnight, Jupiter’s moon “Io” transits the gas giant’s disk. Jupiter is still 40° high in the west at midnight, visible as the brightest point of light in the constellation of Gemini the Twins. Through a telescope, you’ll see Jupiter’s other three Galilean moons lined up west of the planet as Io approaches the southeastern limb. Io’s crossing takes much less time than Ganymede took a few days ago due to Io’s tighter orbit. An hour later, at 1am, Io has reached the middle of the disk. Just minutes after that, Io’s shadow appears at the southeastern limb around 1:05am. By 2am on Saturday, both Io and its shadow are readily visible together on the disk, as Io approaches the western limb and its shadow is nearly central. Io’s transit ends just under 20 minutes later, with the shadow now roughly in the center of Jupiter’s disk. The shadow takes just over another hour to finish crossing.
The 5th-magnitude open cluster M41 sits just 4° south of Sirius. Use binoculars to locate the cluster when the sky is free of troublesome moonlight in early evening. Look the other way from Sirius for the cluster M50. It’s 10° north-northeast from Sirius,
dimmer, smaller and more subtle than M41. Find it by sweeping from Sirius first to Theta Canis Majoris, the 4th-magnitude pointy nose of the Big Dog’s stick figure, then on again nearly as far in the same direction and just a touch to the left. M50 is not exactly easy. You can spot it without much difficulty using 10×50 binoculars through moderate suburban light pollution. Averted vision helps.
Sir John Frederick William Herschel was born on March 7, 1792. An English astronomer and chemist who, as a successor to his father Sir William Herschel, discovered a further 525 nebulae and clusters. John Herschel was a pioneer in celestial photography, and as a chemist contributed to the development of sensitized photographic paper. He also studied physical and geometrical optics, birefringence of crystals, spectrum analysis, and the interference of light and sound waves.