Skywatch Line for Monday and Tuesday, July 31st and August 1st, 2023

This is the Dudley Observatory Skywatch Line for Monday and Tuesday, July 31st and August 1st.

The Sun sets at 8:17 PM; night falls at 10:15. Dawn breaks at 3:50 AM and ends with the Sun rising at 5:47.

Southern Capricornus houses the Moon on both nights. Monday’s Moon rises in 8:07 PM, it appears 33 arc-minutes in size, 99% illuminated, 6° high at 9 PM and sets at 5:04 AM on Tuesday. Tuesday’s Moon becomes “Full” at 2:32 PM, also 33 arc-minutes, 100% lit, but barely visible at 9 PM, rises at 8:49 PM and sets at 6:28 AM on Wednesday. Those who live near coasts can see that tides are much higher than normal.

Venus is largely invisible this month due to its approaching Inferior Conjunction with the Sun on the 13th. Both Mercury and Mars are headed in that direction also and reside in Leo. Mars is 34° from the Sun and appears about 4 arc-seconds, minimum first magnitude but 8° high at 9 PM and sets at 9:44 PM. Mercury is closer to the Sun, zero magnitude, 6 arc-seconds, only 3° high and sets at 9:18 PM; Monday, it lies only 4° below the star Regulus.

Saturn is still the first to rise in southwestern Aquarius at 9:31 PM, glimmering with zero magnitude, a moderate 18 arc-seconds, highest at 2:52 AM and 26° at 5:15 AM. Its rings span 44 arc-seconds in your binoculars or telescope. Saturn is in “retrograde motion” which means that it appears to back up against the stars. Saturn and Jupiter compete for the most moons. Information now lists Saturn with 146 Moons (24 ”regular” and 122 “irregular”). Jupiter is now credited with only 95 moons. Neptune, in southwestern Pisces, is found 21° to Saturn’s left; it rises at 10:18 PM, highest at 4:12 AM and 42° high.

Southeastern Jupiter and Uranus share Aries. Jupiter rises at 12:10 AM, glitters with minus 2nd magnitude, almost 40° in size and 53° high. Uranus brings up the rear, rising at 12:31 AM, almost 4 arc-seconds, and 51° high.

Since we discussed Saturn’s newly found moons, let us consider the Solar System’s natural moons. Earth has only one moon, while other planets have many; in fact, there are over 200 moons in our Solar System. Only Mercury and Venus are without satellites. Most moons orbit their planets in the same direction as the planet’s spin. This points to a common origin with the planet. Some moons are different. Our Moon is believed to be born of a catastrophic collision of Earth and another body. The Earth-Moon system can almost be called a double planet, since the Moon is so large. Most satellite systems are a fraction size of their parent planets. The origin of Mars’ two satellites, Phobos and Deimos, are also of questionable origin. Then there is Triton, one of Neptune’s moons; it orbits in a direction opposite to Neptune’s spin. Some researchers speculate that Triton was part of another system and was captured by Neptune, early in the Solar System’s history.