In the Sky This Month

Sagitta, the arrow, is a small constellation lodged in a prominent part of the sky, between Aquila, the eagle, and Cygnus, the swan. It is high in the southeast as night falls and shoots over to the west as the evening goes on.

Some stars spin so fast that they are shaped more like lozenges than balls. An example is 51 Ophiuchi, in Ophiuchus, which is in the south and southwest at nightfall. The star spins more than 100 times faster than the Sun, causing it to bulge at the equator.

The Moon reaches last quarter at 9:37 p.m. At last quarter, half of the side that faces Earth is bathed in sunlight, while the other half is in darkness. When the Moon is at last quarter it is leading Earth in our planet’s orbit around the Sun.

Aldebaran, the star that marks the eye of the bull, will stand to the lower left of the Moon at first light tomorrow. It will be even closer to the upper right of the Moon on Monday.

Sagitta, the third-smallest constellation, lies between Altair and Vega, two of the stars of the Summer Triangle. Many civilizations saw this pattern as an arrow knifing through the heavens. It stands high over in the northeast at nightfall.

Look low in the east shortly after sunset for a blue-gray band atop the horizon with a thin layer of pink above it, fading into the blue of the daytime sky. The dark band is Earth’s own shadow, which extends far into space.

The “teapot” of Sagittarius steams low across the southwest on late-summer evenings. The spout of the teapot lines up in front of the center of the galaxy, which is about 27,000 light-years away.

The constellation Bootes, the herdsman, stands high in the west in early evening. Its leading light, yellow-orange Arcturus, is one of the brightest stars in the entire sky.

The “evening star” is sneaking up on Spica, the leading light of Virgo. The star is close to the upper right of brilliant Venus as night falls. They will get even closer by Friday night. After that, Venus will move away from the star, adding separation each night.

Orion, the hunter, one of the signature star patterns of winter, is in good view in the early morning sky. Orion clears the eastern horizon a couple of hours before sunrise and is high in the sky at first light.