Moon and Antares on June 22

Star chart showing the moon and Antares.
Look for the moon and Antares, a bright red star, on June 22, 2021.

The June 22 moon and Antares

On June 22, 2021, let the nearly-full waxing gibbous moon introduce you to the star Antares. It’s a red star and the brightest light in the constellation Scorpius the Scorpion.

If the moon is too bright and washes Antares from view, place a finger in front of the moon.

If you can’t see this star’s red color, wait a night or two until the moon has moved away. Or aim your binoculars at Antares.

If your sky is dark enough, also look for the graceful shape of Antares’ constellation Scorpius. It’s one of the easiest constellations to recognize because of the elegant, curved, shape of the Scorpion’s tail.

Read more: Antares in science and skylore

Star chart superimposed over a photo of the Milky Way, with an arrow pointing to Antares.
Outline of constellation Scorpius, with red star Antares at the Scorpion’s Heart. Via
Sphere with roiling red surface with brighter yellow areas on it.
Artist’s concept of the red supergiant star Antares in the constellation Scorpius. Image via ESO/ M. Kornmesser.

Antares is a red supergiant

Any red-looking star that you can see with the unaided eye is either a red giant or red supergiant star. Antares is a red supergiant, a star in the autumn of its years. It’s expected to explode as a supernova one of these days. No telling when, though. It might be tomorrow, or a million years from now.

Although Antares lies way out there, at about 550 light-years distant, this star easily shines at 1st-magnitude brightness. In other words, it’s one of our sky’s brightest stars.

In order to beam so brightly, this star must be extremely luminous, that is, intrinsically very brilliant in and of itself, as opposed to merely appearing bright because of a nearer distance.

Antares’ red color indicates a relatively cool surface temperature, and cool stars actually shine less brilliantly than hot stars of the same size.

But Antares is just so big! Its sheer size makes this star more luminous than many stars with higher surface temperatures.

Read more: Ruby red Antares is the Scorpion’s heart

Gigantic yellow-red circle with dotted line labeled orbit of Mars within it, next to small circle and tiny dot, our sun.
If Antares replaced the sun in our solar system, its circumference would extend beyond the orbit of the fourth planet, Mars. In this illustration, Antares is shown in contrast to another star, Arcturus, and our sun. Image via Wikimedia Commons.

Bottom line: On June 22, 2021, let the moon be your guide to Antares, a red supergiant star.

June 22, 2021

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Bruce McClure

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