EarthSky

July 16th, 2010 - Tonight

This evening, the fat waxing crescent moon shines by the planets Saturn and Mars in your southwest or western sky. For a sky chart of the evening planets, we refer you to yesterday. In the real sky tonight, be sure to notice how the position of tonight’s moon relative to Saturn and Mars has changed since yesterday.

EarthSky’s meteor shower guide for 2010

Tonight’s chart faces a different part of the sky than where the moon and planets reside. They are in the west after sunset. Tonight’s chart has you looking eastward at the famous Summer Triangle. On July 12, we pointed out the blue-white star Vega and its constellation Lyra. Today, it’s Deneb’s turn. Deneb is the northernmost star in the Summer Triangle. Its constellation is Cygnus the Swan. In a dark country sky, you can see that Cygnus is flying along the starlit trail of the summer Milky Way.

One way to recognize the Summer Triangle is notice that there is a cross within the Triangle. The constellation Cygnus is that cross. In fact, the constellation Cygnus is sometimes called the Northern Cross.

Okay, I’ve given you a lot of names here: Summer Triangle, Cygnus, Northern Cross.

Just remember, the constellation Cygnus the Swan contains the Northern Cross. The Cross is – more or less – just another way to see the Swan. The Northern Cross is what’s called an asterism, or recognizable pattern within a constellation. In this case, the pattern is the whole constellation, pretty much. At least, I never see them any differently.

Except for one thing. Deneb is at the top of the Cross, but at the tail of the Swan (the star name “deneb” always means “tail”). The little star Albireo is at the head of the Swan, but at the base of the Cross. Whew!

Our Summer Triangle series includes:
Part 1: Vega and its constellation Lyra
Part 2: Deneb and its constellation Cygnus:
Part 3: Altair and its constellation Aquila