In the Sky This Month

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.

The full Moon is passing through Aquarius tonight. The constellation is home to a planetary system, known as Trappist-1, which contains at least seven planets. All of them are about as big as Earth, and three are in the star’s “habitable zone.”

Mercury, the Sun’s closest planet, is putting on a good show in the morning sky. It is north of due east at dawn and quite low, so you will need a clear horizon to spot it. It’s bright, though, and it will get brighter over the next two weeks.

Look for Mars close to the lower right of the Moon this evening, and staying close to the Moon throughout the night. It looks like a bright orange star. Although Mars has faded over the past month, it’s still one of the brightest lights in the night sky.