Find Hercules between 2 bright stars

Sky chart of constellation Hercules
Hercules is faint. But its mid-section contains the easy-to-see Keystone asterism. Find Hercules between the bright stars Vega in Lyra, and Arcturus in Bootes.

Tonight, try locating one of the coolest constellations up there. The constellation Hercules the Kneeling Giant can be seen ascending in the east-northeast on these Northern Hemisphere spring evenings. You can find Hercules between two brilliant stars: Arcturus and Vega. The chart at the top of this post shows the evening sky in late April, when the constellation Hercules, and the two stars so essential for finding it, are well up in the northeastern to eastern sky.

Arcturus is in the constellation Boötes, and Vega is in the constellation Lyra. At nightfall, Vega may still be below in your horizon. If so, wait a while … it’ll rise soon.

A line between Arcturus and Vega passes through what is known as the Keystone – an asterism, or noticeable star pattern – in Hercules. The Keystone is a squarish figure in the center of Hercules. See it on the charts above and below?

Enjoying EarthSky so far? Sign up for our free daily newsletter today!

Outlines of constellation with parallelogram in center in heavier lines.
The constellation Hercules, with its prominent Keystone asterism marked. Image via Wikimedia Commons.

The Keystone is a helpful pattern for more reasons than one. First, it’s noticeable on the sky’s dome, so it can lead your eye to Hercules.

Also, the Keystone in Hercules can help you find the most fascinating telescopic object within the boundaries of this constellation. This object is a globular star cluster known to stargazers as M13 or the Great Cluster in Hercules. M13 is barely visible to the eye alone in the darkest of skies, but binoculars show it as a nebulous starlike patch of light. And telescopes show stars both on the periphery of the cluster and toward its center.

Star chart, black stars on white background.
The chart shows M13 (the great Hercules cluster) in the Keystone. This chart of the constellation Hercules is via the International Astronomical Union.

This beautiful object is one of the galaxy’s oldest inhabitants. It’s a tightly packed spherical collection of about one million stars.

Read more: M13 or the Great Cluster in Hercules

EarthSky astronomy kits are perfect for beginners. Order today from the EarthSky store

Round region of very very many densely packed stars, density fading off at edges.
M13, aka the Great Cluster in Hercules. This object is a globular star cluster, one of our galaxy’s oldest inhabitants. Photo via ESA/ Hubble/ NASA.

Bottom line: Use the brilliant stars Arcturus and Vega to find the constellation Hercules tonight!

Donate: Your support means the world to us

April 22, 2021

Like what you read?
Subscribe and receive daily news delivered to your inbox.

Your email address will only be used for EarthSky content. Privacy Policy
Thank you! Your submission has been received!
Oops! Something went wrong while submitting the form.

More from 

Deborah Byrd

View All