Originally published by EarthSky.

Brightest star, Sirius: Star chart with Orion, arrow from 3-star Belt to lone star Sirius below.
No matter when you see it in the sky, Orion’s Belt always points to the sky’s brightest star, Sirius. On October mornings, Sirius and Orion can be found in the south before dawn. Southern Hemisphere? Look north and turn this chart upside down.

Watch for the brightest star, Sirius

The planet Venus is up at dawn now. And it’s very bright, much brighter than any other planet or star. But – at this time of year – we always get questions about another bright object in the dawn sky. Andy wrote:

Early this morning, looking south, I saw a beautiful star, bright and multicolored … Can you identify it for me?

And Paula wrote:

This morning two of us got up early. We found a pulsing star straight down the sky below Orion’s Belt. It was pulsing the colors of green, yellow, blue and red like a strobe light. I will search for it every morning as it was so enchanting.

If you’re up before daybreak on these October mornings, take a moment to see this star, which is the sky’s brightest star, Sirius. This star is so brilliant that you can even see it from a light-polluted city. And you can see it if you stay up late, too! It’s rising in the middle of the night now, as seen from around the globe, and is high in the sky – at its best – by dawn.

Want a specific view from your location on the globe? Visit Stellarium and enter your location.

What is that bright twinkling star?

This star is enchanting, so much so that – every year, beginning in Northern Hemisphere autumn – we get many, many questions about a multicolored star twinkling in the southeastern to southern sky after midnight. This star typically turns out to be Sirius, which is in the constellation Canis Major the Greater Dog and is sometimes called the Dog Star.

Why does Sirius twinkle so much?

Sirius appears to flash different colors when it’s low in the sky. Really, all the stars are flashing different colors, because light is composed of all the colors of a rainbow, and the journey through our atmosphere breaks starlight into its component colors via refraction. But you don’t notice the colors of the other stars much, because they’re not as bright as Sirius, which is the brightest star visible from anywhere on Earth.

Since our atmosphere is causing the light to break into its colors, and since Sirius is often seen low in the sky now (where you are peering at it through a thicker layer of atmosphere than when it’s overhead), the flashing colors of Sirius are very obvious. When Sirius is higher in the sky – which it is close to dawn in the month of October – or in the evening sky in January and February – you’ll find that Sirius shines with a steadier, whiter light.

So, on these October mornings, watch as Sirius winks at you in the wee hours before dawn!

Long green line of a meteor above a beach, with constellation Orion and bright star Sirius below it.
View at EarthSky Community Photos. | Daniel Friedman captured this shot from Montauk, New York, on December 13, 2020. Note bright Sirius is on the left, and Orion’s Belt points to it. Thank you, Daniel!

Bottom line: We get many questions about a bright, colorful, twinkling star on these October mornings. It’s the star Sirius in the constellation Canis Major, and the brightest star in the sky. Plus, you’ll know it’s Sirius, because Orion’s Belt always points to it.