Spotlight on the Moon

Skywatchers in North America, and particularly in Quebec, won’t be treated to any special lunar events this month: July’s solar and lunar eclipses won’t be visible from our neck of the woods. But there’ll be plenty of talk about our celestial companion over the coming weeks…

The Apollo 11 lunar module landed on the surface of the Moon at 4:17 p.m. (EDT) on Sunday, July 20, 1969. A few hours later, at 10:56 p.m., Neil Armstrong became the first human to set foot and walk on the lunar surface.

This summer therefore marks the 50th anniversary of the Apollo 11 mission, and the Moon is putting its best face forward all month long for the occasion. Beginning the morning of July 1, a half-hour before sunrise, the thin lunar crescent will join Venus just above the east-northeastern horizon, and on July 3, a half-hour after sundown, it will form a triangle with Mercury and Mars, very low on the west-northwestern horizon.

During the night of July 13-14, the waxing gibbous Moon will hang a few degrees to the left of Jupiter, above the southern horizon, and will appear to chase the giant planet all night long. The following night, the Moon will shine between Jupiter and Saturn against the backdrop of the Milky Way. It will then appear within a hair’s breadth to the right of Saturn during the night of July 15-16 and will pass less than 1 degree below the gaseous planet in the southwest at dawn.

On the evening of July 20—the anniversary of the first lunar walk—the Moon will be in its waning gibbous phase and clearly visible from 11:30 p.m. onward. Illumination conditions will be favourable for observing the famous “lunar seas.” These vast basalt plains, appearing as huge, darker-grey expanses covering almost a third of the Moon’s visible side, are easy to spot. The Sea of Tranquility, which was the landing site for Apollo 11, will be visible to the naked eye or through binoculars near the terminator (the dividing line between the sunlit and night-time hemispheres).

But don’t expect to find the lunar module! Contrary to what one may think, and as big as it may be, the module is impossible to spot with a telescope. That’s doubly true for the American flag, as these objects are simply too small to be seen from Earth. In fact, only in the last few years have probes orbiting the Moon been able to take photos of the Apollo mission landing sites!

The planets in July

Mercury and Mars are hard to spot in the evening sky at the very beginning of the month. The pair will only be visible low over the west-northwestern horizon shortly after sunset and will disappear into the twilight glow in the days that follow. Venus will also be very difficult to view in the morning sky, low on the east-northeastern horizon, about 30 minutes before sunrise. The dazzling Morning Star draws ever closer to the Sun and will also vanish around mid-July.

Hence, the gaseous giants Jupiter and Saturn are the indisputable planetary “stars” of July. Jupiter is visible from nightfall until 2:30 a.m. but sets increasingly earlier with each passing day. Saturn, for its part, is at opposition on July 9, directly opposite the Sun in the sky: It appears in the southeast at twilight and will be visible throughout the night, until it vanishes in the southwest at dawn. But the best time to check out the planet’s famous rings through a telescope will be when it culminates southward in the middle of the night.

Clear skies!