Believe it or not, there are four dogs that are currently traipsing through our early spring skies.
Two are scampering for attention in the west that contain constellations associated with the winter season and will soon be bidding us a fond adieu. But there are two more ascending in the east — a star pattern that will be with us all through spring and summer months. Here, we'll describe each one. It's the 'leash' we can do.
(By the way, if you're looking for binoculars or telescopes to spot the stars of these cosmic pooches, check out our guides for the best binoculars and best telescopes. Our best cameras for astrophotography and best lenses for astrophotography guides can also help you find the right gear for your next starry night photo session.)
The dog star
The brightest of all the stars shines prominently this week about 90 minutes after sunset, about one-third of the way up from the south-southwest horizon. Sirius, the 'Dog Star' is the brightest star of the constellation which bears the Latin name Canis Major — the Big Dog. It is also the unquestionable ruler in its own section of the sky; a truly dazzling object, shining with an unmistakable brilliance. In color, the star is a brilliant white with a definite tinge of blue, but when the air is unsteady it then seems to flicker in rapid scintillation with all the colors of the rainbow. At a distance of 8.7 light-years, Sirius is the fifth nearest star known. Among the naked-eye stars, it is the nearest of all, with the exception of Alpha Centauri.
Four thousand years ago, the ancient Egyptians noticed that Sirius would rise just before dawn at the time of the summer solstice apparently heralding the coming rise of the Nile, upon which Egyptian agriculture and all life in Egypt depended. Hence, Sirius became known as the 'Nile Star' or 'Star of Isis.'
More recently, the scorching heat of July and early August was attributed by some to when Sirius rises with the sun at that time of the year. Its brightness purportedly adds to the sun's energy, producing additional warmth and bringing forth fever in men and madness in dogs. Thus, the term 'Dog Days'.
Overshadowed by Sirius
Maybe you've heard of the idiom: 'The tail wags the dog'. Similarly, Sirius seems to get all the attention compared to the rest of its host constellation.
Indeed, the rest of the constellation of Canis Major is quite overshadowed by the allure and radiance of its most noteworthy star. The rest of the dog is there, composed of triangular hindquarters and a long body. His muzzle and paws are uplifted as though he was bounding across the skies after his master, Orion the Mighty Hunter. Sirius is considered by some to be the Big Dog's nose; others say it marks his dog tag.
Sirius' blinding presence also overwhelms a neighboring star, Adhara, located within the triangle of stars situated to the lower left of the Dog Star. Adhara marks the lower right of the triangle and shines at magnitude +1.50 and ranks as the twenty-second brightest overall in the sky. Yet by virtue of binning, misses by just a shade, the cutoff for first-magnitude classification. Here's another dramatic example of how appearances can be deceiving. Adhara is actually over 1,500 times more luminous than Sirius. But because it's 430 light-years away as compared to just 8.7 for Sirius, Adhara appears only 1/15 as bright.
Orion's 'second hound'
The intriguing names of the constellations may lead one to expect astronomy books to show groups of stars in the shape of a lion, an eagle, a bear and other animals and figures. But many show nothing of the sort. Some books show the constellations as involved geometrical shapes, which in many cases do not look like anything and have no relation to their names. And when darkness falls this week, we see the antithesis of a complex sky pattern in Canis Minor, the Little Dog, Orion's other dog and Canis Major's playful smaller companion.
This smaller canine is situated about halfway up in the south-southwest and almost directly above Sirius. The Little Dog is composed of just two stars. The brighter of these two is the 'Little Dog Star' known as Procyon, the eighth-brightest star in the sky. The fainter of the two is called Gomeisa.
Procyon is a yellow-white star, seven times as luminous as the Sun and 11 light-years away. The name Procyon has been in use since the days of ancient Greece. It is the equivalent of the Latin word 'Antecanis' or 'Before the Dog,' an allusion to the fact that Procyon rises immediately preceding Sirius, and thus heralds the appearance of the great Dog Star. From mid-northern latitudes, Procyon comes above the east-northeast horizon about 25 minutes before Sirius first appears to blaze in the east-southeast.
Interestingly, though, at this time of year, we notice that Procyon actually marches behind its more brilliant companion. How is it possible that the Little Dog rises before the larger one and yet follows it across the southern sky? The answer is that while Procyon is east of Sirius, it is also farther north so that it rises earlier, just as the sun comes up sooner in the morning when it's well north of the celestial equator in the summertime.
Both Canis Major and Canis Minor are associated with the winter season, so they will both soon be departing our evening sky. Sirius and the Big Dog will be gone by the end of April; Procyon and the Little Dog, however, will linger in the west-northwest until the start of June.
Two more hunting dogs in the night sky
About halfway up in the east-northeast sky during the mid-evening hours, this week is a star pattern known as Canes Venatici, the Hunting Dogs. Located about a third of the way from the end of the Big Dipper's handle and below it, these dogs were placed in the sky to assist Boötes, the Bear Driver in his daily task of pursuing the Big Bear (Ursa Major) around the pole of the heavens. They used to be imagined as chasing the Great Bear around the pole.
Like Canis Minor, there are only two stars that mark the Hunting Dogs, the brightest of which is Cor Caroli, known as 'the Heart of Charles.' A popular story is that the star was so-named by Edmund Halley in honor of King Charles II of England. This was supposedly done at the suggestion of the court physician Sir Charles Scarborough, who claimed that 'It shone with a special brilliance on the eve of the King's return to London on May 29, 1660.' However, upon delving deeper into this star's history, it is found that this star's original name was 'Cor Caroli Regis Martyris' honoring the executed Charles I. Cor Caroli marks the position of 'Chara,' one of the two hunting dogs in the mythological outline of the constellation. The other dog is named 'Asterion' and is marked by another, fainter star.
Cor Caroli is noteworthy today because of its high abundance of manganese, silicon, chromium, strontium, and the rare Earth metal europium. Its nonpolitical name, used by astronomers, has become the general term for a class of stars with the same peculiar makeup: the Alpha Canum Venaticorum stars.
Canes Venatici will remain in view all through the rest of the spring and summer, before finally slipping out of sight in the northwest evening sky by early fall.
The constellation of the hot dog
As was noted earlier, both Canes Venatici and Canis Minor are each composed of just two stars. It is hard enough to try and envision a little dog (or anything else for that matter) out of just two stars. When I'm either outside pointing out the stars to campers or inside the 'pretend universe' of a planetarium, I ask my audience to envision the two stars of Canis Minor as a hot dog — but without the bun.
Many years ago, in a pre-recorded sky show at New York's Hayden Planetarium, the lecturer on the tape said: 'You are somehow expected to see a little dog here, using Procyon and a neighboring star.' A voice in the dark called out, 'I see it!' The next line on the tape was, 'If you do see a dog here, perhaps you had better see a doctor too.'
The lecturer's next few lines were hard to hear over the laughter of the audience.
Joe Rao serves as an instructor and guest lecturer at New York's Hayden Planetarium. He writes about astronomy for Natural History magazine, the Farmers' Almanac and other publications. Follow us on Twitter @Spacedotcom and on Facebook