A couple of weeks ago we
looked at members of the cat
family in the evening spring sky. So this week, to give equal time to dog
lovers, we'll examine some of the star patterns that are dedicated to dogs.
In our current evening sky,
there are four canines in view as darkness falls.
In one of these, shines
the brightest of all stars. You can see it blazing prominently low in the southwest.
Sirius, the "Dog Star," is the brightest star of the constellation
which bears the Latin name Canis Major -- the Greater Dog. It is also the unquestionable
ruler in its own section of the sky; a truly dazzling object.
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. Its color appears a brilliant
white tinged with a distinctive bluish hue.
An admirer of Sirius once
compared its sparkle to that of a brilliant diamond. Its name appears to be
derived directly from the Greek word for "sparkling" or "scorching,"
and one can understand how it received these titles upon seeing as it approaches
its setting, which occurs nowadays at around 10:00 p.m. local daylight time.
When at such a low altitude, the thicker layer of air near to the horizon causes
its light to scintillate rapidly, causing it to seem to flicker with all the
colors of the rainbow.
Ironically, this is when
Sirius seems to attract the most attention; people call their local planetariums
inquiring about "that strange and colorful UFO that was dancing above the
west-south horizon."
The rest of the stars of
Canis Major, with some imagination, can be made out to somewhat resemble a dog.
In his classic sky guide, "The Stars/A New Way to See Them," the late
H.A. Rey (1898-1977) used Sirius for a dog tag.
The antithesis of the complex
pattern of the Big Dog can be found in Canis Minor, the Little Dog. It is composed
of just two stars (perhaps instead of the Little Dog, we should call it the
"Hot Dog!").
The brighter of these two
stars is the "little Dog Star," known as Procyon, the eighth brightest
star in the sky. It is a yellow-white star, six times as luminous as the Sun.
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 about 20 minutes before Sirius (at
midnorthern latitudes), and thus heralds the appearance of the great Dog Star.
Lastly, now soaring high
in our eastern evening sky are the Hunting Dogs, known as Canes Venatici. 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 Boö tes, the Bear Driver in
his daily task of pursuing the Big Bear (Ursa Major) around the pole of the
heavens. 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.
In this region of the sky
are several interesting deep-sky objects, which are all worth looking for with
a telescope. One of these is Messier 3, a beautiful, bright and condensed globular
star cluster. It was discovered by Charles Messier in 1764 and can be seen as
a hazy sixth-magnitude "star" in binoculars (Sixth magnitude is on
the limit of naked-eye visibility).
There are also three faint
galaxies in this region of the sky, located between Canes Venatici and the Big
Dipper's handle. Just to the north and forming an isosceles triangle with the
dogs two stars is Messier 94, a very compact spiral galaxy. Photographs of M94,
which is about 20 million miles away, strongly resemble a hurricane that lacks
an eye.
Messier 63, about 35 million
light-years distant, appears nearly twice the size of M94. Photos show a very
narrow pattern of spiral arms resembling some vast celestial flower. For this
reason this galaxy has received the popular name Sunflower, though in a modest
telescope it appears only as an oval haze.
Nearby is Messier 51, the
famous
Whirlpool Galaxy, 35 million light-years away, was the first observed nebula
in which a spiral structure was observed, in 1845, by Lord Rosse with his giant
six-foot reflector at Parsonstown, Ireland. A small telescope shows it as a
pair of hazy spots; each one the center of two connected galaxies.
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Joe Rao
serves as an instructor and guest lecturer at New York's Hayden Planetarium.
He writes about astronomy for The New York Times and other publications, and
he is also an on-camera meteorologist for News
12 Westchester, New York.
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