Stargazing: Canis Major’s 'dog star' shimmers in night sky

Stargazing: Canis Major’s 'dog star' shimmers in night sky

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At this time of year, the southeastern sky is host to a star that often appears as if it is “shivering” especially when viewed with a pair of binoculars.

That star, Sirius (SEER-ee-us), located in the constellation of Canis Major, the Great Dog, is a brilliant white star and, next to our Sun, is the brightest star we can see from our vantage point in the northern hemisphere.

Located nearly 9 light years away from Earth (which is a good thing), it is a gigantic star whose illumination is 50 times as bright as our parent Sun.

Although visible in the night sky now, it is during the daytime of late summer months that this star gets a bad rap because of summertime heat.

People don’t refer to that time of year as the “Sirius days of summer” it is always the “dog days of summer” and often they have no idea as to where that saying came from.

Being the brightest star in its parent constellation, Sirius is nicknamed the “dog” star and ancient cultures knew it was directly overhead during the late summer and believed its intense light just added to the heat they were enduring.

Why the “shivering” appearance of Sirius?

Starlight traveling through space passes through a variety of air densities and when it gets to Earth it’s the atmospheric refraction of this starlight that causes the twinkling we see. The technical term for that twinkling is scintillation.

Just to the right of Sirius is a fairly bright star named Beta Canis Major. It is also in the same constellation as Sirius but it’s Arabic name of Murzim means “proclaimer” because it rises before Sirius appears thereby heralding its arrival.

Sirius is actually a double star although its companion is classified as a white dwarf. This white dwarf star is called “The Pup.”

When I am giving a talk to groups there are some attendees who have told me they sometimes have trouble understanding what I write about because the subject matter is so complex.

In trying to write about “The Pup” I can understand how they came to that opinion. Consider this: “The Pup” is about three times the size of Earth but has 250,000 times our mass. One cubic inch of its mass would weigh a ton, a cubic yard of material 40,000 tons. Talk about complexity.

As we close out the first full week of the New Year, another bright object in the sky is represented by our “sister’”planet Venus now located about 16 degrees above the southwestern horizon shortly after sunset shining at a magnitude of –4.0.

Venus gets its name from the Roman goddess of love and beauty that may, in part, be due to the brightness of the planet and may date back to the Babylonians in 1581 who referred to Venus as “bright queen of the sky.”

Lying between Earth and the Sun, Venus is designated an inferior planet and as such it exhibits some phases of illumination not unlike those of our own satellite, the moon.

Currently, illuminated about 72%, Venus is best viewed with binoculars during our evening twilight. Observing the planet at that point in time will significantly reduce the planet’s intense reflection and glare of sunlight off it’s surrounding cloud structure.

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