A Morning Moon, Mars on the Move, and Venus and Jupiter Kiss at Sunset!
The Moon and Planets
At 11:41 pm on Wednesday evening, the Moon reaches Last Quarter. At that moment, the Sun, Earth, and Moon form a 90 degree angle in space, so we see the Moon half lit — from the east. For the rest of the week, it swings towards the sunrise, closing the angle, and reducing the amount of our side that is illuminated. Meanwhile, the far side becomes more and more filled with light. There is no dark side of the Moon!
The days surrounding first and last quarter are the best for seeing the topography of the Moon illuminated by steeply slanted sunlight that casts long dark shadows behind mountain peaks and crater rims. But Last Quarter Moon observers need to stay up late, or rise early, because it’s a pre-dawn object. Last Quarter Moons rise after midnight and remain visible in morning daylight in the south and western sky.
Speaking of early rising, on Thursday morning, August 25, the Moon will occult (or temporarily pass in front of) a medium bright (magnitude 3.6) star in Taurus the Bull named Hyadum I. The star marks the chin of Taurus’ triangular face. The event can be observed with unaided eyes, binoculars, and any sized telescope. At 4:53 am EDT, the Moon’s steady eastward motion will carry it between us and the star.
For northern hemisphere observers, the star will be to the Moon’s right, i.e., the lit up half. (Be sure to start watching a few minutes beforehand as the time may be slightly different for your longitude.) At 6:07 am, the star will emerge from behind the opposite, dark half of the Moon. For the Eastern time zone, emersion occurs in a brightening sky, but binoculars or a telescope trained on the right hand edge should pick it up as it re-appears. While you wait, be sure to enjoy the soon-to-arrive winter sky objects, including The Pleiades and Orion the Hunter.
Mercury, Venus, and Jupiter are situated in the low western sky after sunset. Mercury is a bit too dim and low to spot, but bright white Venus and almost as bright Jupiter are readily visible if you know where to look. All week, they are about 20° (or two fist diameters) to the south of the Sun. Tonight (Sunday) the two planets are 6° (a palm’s width at arm’s length) apart, with Jupiter to the upper left (further south) of Venus. Every evening this week, they move towards one another, culminating in a rare close grouping on Saturday evening, August 27th, when they will be so close together that they will appear as one bright object to unaided eyes! In fact, they will be only 6 arc-minutes apart (one twentieth of the Moon’s diameter) and they’ll easily fit together in your telescope’s field of view! This is a worldwide visible event that won’t occur again until 2065, so let’s hope for clear western skies after sunset!
To see them, you’ll need a low, cloud-free western horizon. You can start looking for them beforehand, but wait until the Sun is safely down, about 8 pm, before using binoculars or a telescope. At sunset, the planets will be about 10° above the horizon. They set just before 9 pm local time. I suggest you start practicing finding them now, so you’ll know where to look on Saturday.
Despite being much farther from Earth now, reddish Mars continues to catch the eye in the evening southwestern sky. It’s not alone, AND it’s on the move! As darkness falls, Mars is about 20° (two fist diameters) above the southern horizon. Dimmer, yellowish Saturn sits about 4.5° (four finger widths) above Mars, and the twinkling bright reddish supergiant star Antares sits about 2° below Mars. Tonight (Sunday), Mars is slightly offset to the west (right) of Antares and Saturn. Every evening, Mars hops a finger width eastward, landing between Antares and Saturn on Tuesday and Wednesday evenings, and then pulling away. This group of objects sets just before midnight this week.
The Solar System’s two ice giant planets, Uranus and Neptune, rise by about 10 pm this week. Due to their extreme distance, they change location very little from week to week.
While the Moon is out of the evening sky this week, look just to the east of Mars for the Teapot-shaped stars of Sagittarius the Archer, and the “steam” of the Milky Way rising from the teapot’s spout, from the southern horizon. (More about this soon.) And, if you missed last week’s tour of the “Tim Hortons” constellation Lyra the Lyre, it’s here.
Stargazing News for this week (from August 21st) by Chris Vaughan.
