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See Sirius, the sky’s brightest star


Tonight is Oct 13, 2015

Moon Phase Courtesy U.S. Naval Observatory

View larger. | Brightest star Sirius on left, with constellation Orion. See how three stars of Orion’s Belt point to Sirius? This photo from EarthSky Facebook friend Susan Jensen in Odessa, Washington. Thank you, Susan!

Tonight, stay up very late – or get up early tomorrow morning – to see the sky’s brightest star.

Andy wrote:

Early this morning, looking southeast, 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.

This star is enchanting, so much so that – every year, beginning in N. hemisphere autumn – we get many, many questions about a multicolored star twinkling in the southeastern to southern sky after midnight. This star is Sirius in the constellation Canis Major the Greater Dog. It’s sometimes called the Dog Star. Sirius is now rising in the southeast in the hours after midnight and can be found in the south at dawn. Notice that a line from Orion’s Belt points to Sirius.

Sirius appears to flash different colors when it’s low in the sky … really, all the stars are flashing different colors. That’s because light is composed of all the colors of a rainbow, and the journey through our atmosphere breaks starlight into its component colors (refraction). But you don’t notice the colors of the other stars as 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 only visible 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.

But when Sirius is higher in the sky – which it is close to dawn – or in the evening sky in late winter – you’ll find that Sirius shines with a steadier, whiter light. On these chilly October mornings, however, watch as Sirius winks at you in the wee hours before dawn!

By the way, there are two bright planets up before dawn now, both brighter than Sirius. Venus and Jupiter are closer to the sunrise, in the east before dawn.

More about Sirius: Dog Star and brightest star

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, brightest star in the sky. The bright planets Venus and Jupiter are also up before dawn now. But you’ll know Sirius, because Orion’s Belt always points to it. See it tonight!

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