Skywatch Line for Monday and Tuesday, April 30th and May 1st, 2018

This is the Dudley Observatory Skywatch Line for Monday and Tuesday, April 30th and May 1st written by Joe Slomka.

The Sun sets at 7:55 PM; night falls at 9:45. Dawn breaks at 3:59 AM and ends with sunrise at 5:49.

Early twilight contains only one bright planet – Venus. In Taurus, it blazes at minus 4th magnitude and appears about 88% illuminated in our binoculars and telescopes. At about 8:25 PM, it is about 18º high in the southwest and sets at 10:16 PM.

Monday’s Moon, one day after “full,” rises in Libra only 5º from Jupiter at 8:36 PM. Tuesday’s Moon rises about an hour later, is slightly dimmer and thinner and located in Scorpius. It is best observed at 1:54 AM on Tuesday and 2:42 AM on Wednesday.

Also, in Libra, Jupiter rises almost simultaneously with the Moon. But shines at minus 2nd magnitude and appears about 44 arc-seconds in size. Jupiter is approaching opposition and is up almost all night. Telescopic observers can see the Great Red Spot (a giant storm) at 12:49 AM, Tuesday. Monday at 9:02 PM, the Jovian moon IO’s shadow begins to cross the planet, followed by IO itself at 9:14. The shadow leaves Jupiter at 11:12 PM, trailed by IO at 11:23. Jupiter is best seen at 1:28 AM.

Dwarf planet 1Ceres is tonight’s challenge object. The 8th magnitude body lies about 3º from Leo’s nose, appearing about ½ arc-second in size. Finder charts, in astronomical media, are required to locate this tiny member of our Solar System.

Saturn and Mars share Sagittarius. The Ringed Planet rises first at 12:23 AM. By Dawn, it gleams with zero magnitude and appears about 24º high in the East. Saturn’s rings present marvelous views to first-time viewers. Mars, 14º below Saturn, rises at 1:29 AM. By Dawn, is glows at minus zero magnitude, appears 88% illuminated and is 18º high.

Mars also is now becoming worthy of prolonged observation. During May, Saturn slightly brightens and appears a bit larger. Mars, on the other hand, brightens faster and also is markedly larger in our instruments.

Since the almost full Moon dominates tonight’s sky, let’s consider our nearest neighbor. Astronomers have long wondered about the Moon’s origin. Before lunar landings, three theories predominated. The first hypothesized that the Moon was literally spun off of a rapidly rotating Earth. The second was that the Moon was formed by leftovers from Earth’s formation. The third theorized that a wandering Moon was already formed elsewhere in the Solar System and captured by Earth’s gravity. Due to Apollo lunar landings, which brought back moon rocks, a new hypothesis resulted. This theory, supported by moon rock analysis, said that the Earth was hit by a Mars-sized body, which broke off pieces of Earth. Those pieces formed a temporary ring and later coalesced into the Moon.

The Moon’s gravity causes tides on Earth. In fact, in the far distant future, lunar gravity will slow the Earth’s rotation to the point that it will present the same face to the Moon, just as the Moon now shows the same face to Earth.

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