This is the Skywatch Line for Monday and Tuesday, May 16th and 17th.
The Sun sets at 8:13 PM; night falls at 10:14. Dawn begins at 3:29 AM and ends with the Sun rising at 5:30.
The ten-day-old Moon dominates the darkening sky. In Virgo, it blazes at minus 10.9 and appears about 80 percent illuminated; Tuesday night finds it even brighter and larger. The Moon sets during Dawn both days.
Jupiter, still in Leo, is also up during twilight. Observers get a two-for-one treat Monday night. Binocular observers, at 9:57 PM, will see all four Galilean moons to one side of the giant planet. At the same time, telescopic observers will see the Great Red Spot, a giant storm, centered on Jupiter’s face. Jupiter sets about 2:46 AM.
Mars rises during civil dusk in Scorpius. As mentioned last week, it is retrograding – moving westward away from Saturn.
Saturn rises in Ophiuchus at 9:26 PM. Antares, the brightest star in Scorpius rises shortly after Saturn. By Midnight, they are high enough for observation. Mars is brightest and blazes at minus 2 magnitude. Saturn is next brightest at zero magnitude, with Antares third at first magnitude. They form a giant triangle in the southern sky. Mars is eleven degrees West of Saturn and seven degrees above like-colored Antares. Saturn completes the triangle by being almost eight degrees away from Antares. All three set after sunrise.
Eighth magnitude Neptune rises at 2:34 AM and appears as a blue green dot in Aquarius. Uranus, in Pisces, rises at 4:04 AM. Observers trying for these outer planets should begin before Dawn, when sunlight will wash out these tiny images.
Last Monday, we observed Mercury transiting across the Sun’s face. Most people know that Mercury is the planet closest to the Sun. Over a 150 years ago, that was not certain. Urbain Leverrier, a French astronomer, had just discovered the planet Neptune by analyzing oddities in the orbit of Uranus, and using Newton’s laws. Astronomers, for some time, knew of similar problems with Mercury’s orbit. Some of these issues were solved, again using Newton’s laws, but others remained unexplained. Leverrier took up the problem. He predicted that a planet could exist between the Sun and Mercury, if it had a certain orbit. In 1859, a French amateur astronomer, Edmond Lescarbault, claimed to have spotted it. Leverrier interviewed Lescarbault, proclaimed his discovery real and appropriately named the new planet Vulcan, after the Roman god of fire. However, another French astronomer named Liais was observing in Brazil at the same time as Lescarbault, and did not see it. Other reports had similar mixed results. Two New York astronomers, Lewis Swift and Christian Peters, who once headed Dudley Observatory, observed during an eclipse in 1878. They failed to find Vulcan, only sunspots. In 1915, Albert Einstein solved the mystery and discredited Vulcan. His Theory of Relativity predicted that Mercury’s orbital precession was due to Relativity effects. Several space probes now orbit the Sun and provide constant imagery; no planet has been seen. It is possible that small asteroids could orbit between Mercury and the Sun, but none have been found to date.