On July and August evenings, look for the constellation Corona Borealis, also known as the Northern Crown. However, you’ll need a dark sky to see it. If you have one, the constellation is easy and distinctive. In fact, it makes the shape of the letter C. Then, in the middle of the C is a white jewel of a star. This star, the brightest light in the Northern Crown, is called Alphecca or Gemma.
To see this famous C-shaped pattern of stars from the Northern Hemisphere, you’ll be looking high overhead during the evening hours in July and August. From the Southern Hemisphere, the constellation is low in the northern sky.
Look for Corona Borealis between 2 bright stars
The Crown is located roughly along a line between two bright stars. The first is the orange star Arcturus in the constellation Boötes the Herdsman. The second is beautiful, blue-white Vega in the constellation Lyra the Harp.
Arcturus has already passed its highest point in the evening at this time of year and is slowly descending to the west. However, Vega is still high in the east in July and overhead in August evenings. With dark skies you’ll notice the orange color of Arcturus and Vega’s bright blue-white tinge.
Corona Borealis is between these two stars, though closer to Vega. Remember, a dark sky is best for seeing this faint semicircle of stars.
Or find it between two constellations
Gem of the Northern Crown
The brightest star in Corona Borealis is Gemma at magnitude 2.21. The meaning of this Latin star name should be obvious. This star is the gem of the Northern Crown. It is 75 light-years distant.
But, as is the case with many stars, this star has more than one name. It’s also called Alphecca. This second name is from an Arabic phrase meaning the bright one of the dish. So you can see that, throughout history, stargazers have identified Corona Borealis with a common shape: a bowl, a disk, or a crown.
By the way, Gemma, aka Alphecca, is an eclipsing binary system. It consists of a smaller sunlike star that passes in front of a brighter star every 17.4 days, as seen from our earthly vantage point.
Other bright stars in the Northern Crown
The second brightest star, Beta Coronae Borealis, has the name of Nusakan. Nusakan shines at magnitude 3.65. Nukasan and Alphecca are a little less than three degrees apart. Nukasan lies 114 light-years away.
The other stars that make up the curved shape of Corona Borealis are all 3rd and 4th magnitude. Theta lies on the other side of Nukasan and Gamma and Delta lie on the other side of Alphecca. Also, Gamma is a double star, but the two are very close and require high magnification and steady skies to see.
Bottom line: On July and August evenings, look for Corona Borealis’ graceful semicircle of stars between the two bright stars Arcturus and Vega.