The Moon slides along one of the horns of Taurus tonight. At nightfall, the bull’s bright eye, the star Aldebaran, is to the lower right of the Moon. And the tip of the horn, El Nath, is closer to the left or lower left of the Moon. By the time they set, in the wee hours of the morning, El Nath will stand close above the Moon.
The Moon is in its “waxing gibbous” phase. “Gibbous” means the Sun is lighting up more than half of the lunar hemisphere that faces our way. “Waxing” means that more of that half is being lit up every night. The Moon will keep getting “fatter” until it’s full, a week from today.
“Gibbous” comes from a Latin word that means “hump.” It can be applied to anything that appears to have a hump on its back, such as a camel. A gibbous Moon appears to have a hump on top of its round half.
Planets can appear gibbous as well. Mercury and Venus are inside Earth’s orbit around the Sun, so they can follow the same cycle of phases as the Moon — from thin crescents to almost full. We don’t see them as new or full because, during those phases, they’re passing between Earth and the Sun, or behind the Sun.
Planets outside Earth’s orbit never appear in a crescent phase, but they can appear gibbous, depending on our viewing angle.
Stars, on the other hand, are always full. They generate their own light, so the viewing angle doesn’t matter — unlike the Moon, which will have a “hump” on its back for another week.