This is the Dudley Observatory’s Skywatch Line for Monday and Tuesday May 16th, and 17th, written by Joe Slomka.
The Sun sets at 8:12 PM; night falls at 10:13. Dawn begins at 3:30 AM and ends with the Sun rising at 5:31.
The Full Flower Moon was officially Full after its Total Eclipse last night. Monday, the Moon rises at 9:16 PM, 33 arc-minutes in size, 99% illuminated and sets at 6:24 AM Tuesday. Note that Monday’s Moon rises with the bright star Antares, only 2° below; a great binocular view. Tuesday’s Moon resides in Scorpius, the same size but slightly thinner, rises at 10:35 PM and sets at 7:17 AM, Wednesday.
Mercury is the only evening planet, but not for long. We mentioned, last week, that Mercury was fading. Monday, it sets at the Civil Twilight (8:45 PM). The planet is preparing for Inferior Conjunction May 21st, after which it becomes a Dawn planet.
The Planetary Parade continues, but with Uranus missing; it sets before sunset. The first to rise is brilliant southern Saturn; it rises in Capricornus at 2:03 AM, shines with zero magnitude, a moderate 16 arc-seconds and is 26° high by Civil Dawn (4:58 AM). Pisces houses Neptune, Jupiter and Venus. Neptune, 30° to Saturn’s East, is next, rising a 3:13 AM, glowing with 8th magnitude, 2 arc-seconds and 19° high. Mars, 15 arc-minutes from Neptune, rises at the same time as Neptune, also 8th magnitude, 6 arc-seconds in size and also 19° high. Mars is becoming more prominent; Tuesday, Mars and Neptune are in conjunction, only 0.6° apart. Jupiter, the fourth to rise at 3:47 AM, shines with minus 2nd magnitude, a large 36 arc-seconds and also 19° high. Finally, Venus brings up the rear, rising at 4:03 AM, blazing with minus 4th magnitude, a moderate 15 arc-seconds, 73% lit and 10° high. All set during daytime.
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 challenge and predicted that a planet could exist between the Sun and Mercury, if it had a specified orbit. In 1859, a French amateur astronomer, Edmond Lescarbault, claimed to have spotted it. Leverrier interviewed Lescarbault, proclaimed his sighting 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.