Canes
Venaticiwas delineated by Johannes Hevelius to represent Asterion and Chara, the two dogs of Boötes as he hunted the northern skies for the bears, Ursa Major and Ursa Minor. You can find these hounds by looking to the right of Boötes and south of the tail of the Great Bear. But you will have to look closely, for the brightest star of the 23 that Hevelius described is but magnitude 2.9. This is Cor Caroli—a fine double star. If, on a mid-May evening at about 9:30 or ten o'clock, you were to drop a plumb bob from Cor Caroli, it would come to Earth somewhere in the vicinity of Sonoma or Napa, in Northern California. It was Edmond Halley who named Cor Caroli in honor of King Charles II of England.
There are only two other stars bright enough to merit names of their own. Chara is Beta-Canum Venaticorum; and there is a star of magnitude 5.5 that has been called La Superba, a peculiar type of star with “superbly flashing brilliancy of its prismatic rays.” It is a brilliant red star whose light varies over a period of half a year between magnitude 5.2 and 6.6.
But what the Hunting Dogs lack in bright stars, they make up for with a wealth of galaxies. Five Messier objects are among the hundred deep-sky objects that may be found with even a small telescope. M51 is the Whirlpool Galaxy (NGC 5194), one of two connected galaxies—a pretty face-on spiral galaxy joined at the end of one of its spiral arms to the irregular galaxy NGC 5195. A 10- or 12-inch telescope and a dark sky are needed to discern the spiral arms, while smaller telescopes or large binoculars should reveal two fuzzy dots.
The Hubble Space Telescope has snapped a
view of several star generations in the central region of the
Whirlpool Galaxy (M51), a spiral region 23 million light-years
from Earth in the constellation Canes Venatici. The galaxy’s
massive center, the bright ball of light in the center of the
photograph, is about 80 light-years across and has a brightness
of about 100 million Suns. Astronomers estimate that it is about
400 million years old and has a mass 40 million times that of
our Sun. The concentration of stars is about 5,000 times higher
than in our solar neighborhood, the Milky Way. The dark Y across
the center is a sign of dust absorption. The bright dot in the
middle of the Y has a brightness of about one million suns, but
a size of less than five light-years. Its power and its tiny size
suggest that we have located the elusive central black hole that
produces powerful radio jets. Surrounding the center is a much
older stellar population that covers a region of about 1,500 light-years
in diameter and is at least 8 billion years old, possibly as old
as the Universe itself, about 13 billion years. Further away,
there is a “necklace” of very young star-forming regions,
clusters of infant stars, younger than 10 million years, which
are about 700 light-years away from the center. Normally, young
stars are found thousands of light-years away. Astronomers believe
that stars in the central region were formed when a dwarf companion
galaxy—which is not in the photograph—passed close to
it, about 400 million years ago, stirring up dust and material
for new star birth.
The
large globular cluster, M3 (NGC 5272), shows as a pretty ball
of sparkling points in this CCD photo by Conrad Jung, taken with
his 6-inch Maksutov.