This is Dudley Observatory’s Skywatch Line for Friday, March 10, through Sunday, March 12, written by Sam Salem.
On Friday, Sun rises at 6:16am and sets at 5:56pm; the 96% illuminated Waxing Gibbous Moon reaches transit altitude of 57 degrees south at 11:00pm and sets before sunrise at 5:12am. The Daylight Saving Time begins at 2:00am on Sunday. Saturday night’s Moon will appear full to the eye all night long. However, the Moon turns exactly full on Sunday at 10:54am.This is the third full Moon this year, which is called the Worm Moon, Crow Moon, or Sap Moon. This full Moon is the closest to the March 20 Spring Equinox. On Sunday night, look eastward as darkness falls to see the Moon. Watch for Jupiter to follow the Moon into the night sky by early evening. The Moon and Jupiter will climb upward during the evening hours, reaching their high point for the night somewhat after midnight.
As darkness falls on Friday, Regulus, the brightest star in the constellation Leo, the Lion, appears near the Moon. The Moon will be 2.5 degrees lower left of Regulus. Spotting Regulus in the glare of the Waxing Gibbous Moon might not be easy. Regulus is one of the four Royal Stars of ancient Persia. These Royal Stars, Regulus, Antares, Fomalhaut, and Aldebaran, mark the four quadrants of the sky. Thousands of years ago, the Royal Stars defined the approximate positions of Equinoxes and Solstices in the sky. Regulus, often portrayed as the most significant Royal Star, ruled as the summer Solstice star, Antares as the autumn Equinox star, Fomalhaut as the winter Solstice star, and Aldebaran as the spring Equinox star.
Uranus, at 5.9 magnitude, resides in constellation Pisces in the west at nightfall between Mars and Venus. Direct observations of Uranus rings from Earth had not been possible because the rings are lost in the planet’s glare as seen through terrestrial optical telescopes. Friday marks the 40th anniversary of the discovery of Uranus’ rings from Earth. On March 10, 1977, a star occultation with Uranus unexpectedly revealed its rings. The ringed planet blocked the starlight, but the star disappeared from view five times. This data suggested that Uranus was surrounded by at least five rings. Four more rings were suggested by subsequent occultation measurements from the Earth, and two additional ones were found by space probe Voyager 2. Two outer rings were found in 2003–2005 in Hubble Space Telescope photos. William Herschel, who uncovered Uranus in 1781, reported observing a ring system around Uranus more than 200 years ago. It is not known whether something had caused the rings to brighten at that time, or was Herschel’s observation in error.
Saturday marks the birthdate of the French Astronomer Urbain-Jean-Joseph Le Verrier. Born in 1811, Le Verrier predicted by mathematical means the existence of the planet Neptune. He calculated the position of Neptune from irregularities in Uranus’s orbit. As his contemporaries described it, he discovered a planet with the tip of his pen, without any instrument other than the strength of his calculations alone. In 1856, the German astronomer Johan G. Galle discovered
Neptune within one degree of the position that had been computed by Le Verrier, the same night he received the coordinates. The discovery of Neptune is one of the most remarkable moments of 19th century science giving the most striking confirmation of Newton’s theory of gravitation.