Insider’s Guide to the Galaxy – Observing Suggestions for mid-April

The multiple star Castor in Gemini, as viewed in a telescope.

While the moon is bright in the night sky, it’s still possible to view the brighter stars with your unaided eyes, and you’ll see even more through binoculars and backyard telescopes.

Double stars are sets of two (or more) close-together stars. In many cases, the partner stars show differences in colour and/or brightness, making them fun and easy to look at. They can be gravitationally bound together, orbiting one another on times scales of years to decades or centuries. We can such systems binary stars.

Stars can also appear to be close together in the sky, even though they are actually completely unrelated to one another. They just happen to sit in the same direction, as viewed from Earth. We call those line-of-sight double stars.

Binaries or double stars that sit wide apart from each other can be seen with your unaided eyes. An example of that is the star Mizar, which marks the bend in the Big Dipper’s handle. A small star next to it named Alcor can be seen by most people with just their eyes.

Closer together binaries and doubles can be seen in binoculars – such as Sigma Orionis, a multiple star located just below Orion’s left-hand (eastern) belt star. Another pair is Theta Tauri, located just below the bright star Aldebaran.

Telescope-worthy double stars are Castor in Gemini (the Twins), Meissa in Orion (the Hunter), Izar in Bootes (the Herdsman), Cor Corali in Canes Venatici (the Hunting Dogs), Algieba in Leo (the Lion), and Polaris in Ursa Minor (the Little Bear). After ten pm, the fantastic Double Double Star, also known as Epsilon Lyrae, rises.

Have a go at looking at these stars on the next clear night! Stellarium can show you where they are. In a future session, we’ll cover doubles in more detail.