Spot the dogs in the night sky
As anyone interested in observing the night sky knows, Sirius is the brightest star in the night sky. Located in the constellation of Canis Major — the Big Dog, and situated to the lower left of the constellation of Orion — the Hunter, Sirius is often referred to as the Dog Star.
Canis Major, along with Canis Minor — the Little Dog, are Orion's four-legged hunting companions. From the ancient Greek seirios, meaning glowing or scorching, Sirius was considered a bad omen by the ancient Romans, who were said to sacrifice dogs to protect their crops from disease, which they associated with the presence of the star in the night sky. The ancient Greeks believed Sirius affected the behaviour of dogs during the hottest part of the summer, what they called the dog days, from which we inherited the phrase the dog days of summer to denote abnormally warm weather during the summer months.
ALL ABOUT SIRIUS
Sirius is a binary star system, consisting of a hot, white primary star (Sirius A), and a tiny pup white dwarf star (Sirius B). The Sirius binary system is thought to have originally consisted of two large, bright, bluish stars, with one of them eventually evolving into a red giant, shedding its stellar atmosphere, and collapsing into a white dwarf (Sirius B).
Sirius A is twice as massive as our Sun, and 25 times brighter. At magnitude -1.46, Sirius is located 8.6 light-years (lys) from Earth, making it one of our nearest stellar neighbours; it's the fifth closest star to Earth. For the next 60,000 years, Sirius will slowly move closer to our planet, gradually brightening as it does; it will then begin to move away from Earth but will remain our brightest star in the night sky for approximately the next 210,000 years.
Although it was important to numerous ancient cultures, Sirius was particularly important to the ancient Egyptians. Due to its heliacal rising (which occurs when a star, after being behind the sun — and thus unobservable for a season — appears above the eastern horizon just before sunrise), Sirius marked the pending annual flooding of the Nile River. Its appearance afforded the Egyptian farmers time to move their livestock and temporary buildings from the river's delta area.
OTHER DOG STARS
The other dog star in the night sky is Procyon, the brightest star in the constellation of Canis Minor — the Little Dog, to the upper left of Orion. At magnitude +0.34, Procyon is the eighth brightest star in the night sky, situated a mere 11.46 lys from Earth.
It, too, is a binary star system, consisting of a hot, white, primary (Procyon A) and a small companion, white dwarf star (Procyon B). The name Procyon comes from the ancient Greek Prokyoh, meaning "before the dog," referring to the fact that Procyon precedes Sirius across the night sky, due to Earth's rotation.
Orion, Canis Major (with Sirius), and Canis Minor (with Procyon) are all prominent in the mid-evening, winter night sky, about onethird of the way up the sky above the southern horizon. On a clear, crisp winter's evening, away from city lights, these three constellations and their bright stars (especially Sirius) are breathtaking. If you have your binoculars or are using a telescope, have a look at the magnificent Orion Nebula hanging below the middle star of Orion's belt. As well, have a look at Betelgeuse (a large, red, variable star, magnitude +0.6- +1.6) in Orion's upper left-hand corner, and Rigel (a variable, blue supergiant, magnitude +0.05 - +0.18) in the lower right-hand corner.
THIS WEEK'S SKY
Mars (magnitude +0.6, in Aries — the Ram) remains the only planet visible again his coming week.
The other bright planets (Mercury, Venus, Jupiter, and Saturn) are too close to the sun to be readily observable and Mercury achieves inferior solar conjunction (passing between Earth and the sun) on Feb. 8.
Visible around 6:10 p.m., 61 degrees above the southern horizon as the dusk sky darkens, Mars remains observable until it sets in the southwest around 1:20 a.m. Next week, we'll look at NASA's Mars 2020 landing on the Red Planet on Feb. 18.
Until next week, clear skies.
EVENT
• Feb. 11 — New moon