Check out this month's star chart (May) and you'll notice that the Milky Way is confined to the northern horizon. Look up in the evening this month and you're looking out of the thin side of the Milky Way galaxy.
The first thing that's noticeable about the spring sky is how sparse the stars are. Gone are the bright stars of winter. Gone is Orion and his merry band. Yet to come is the Summer Triangle, the split Milky Way, and the gold mine of faint wonders in Sagittarius and Scutum. So the spring skies may seem like the intermission between two acts of a play.
In May 1997's Exploring Spring Deep Sky Objects I covered, in general, the many galaxies of the Virgo Cluster visible in the spring. This time we'll look at more wonders near and far.
The first near wonder is an open star cluster. These are also called galactic star clusters, because they lie along the plane of the galaxy. The other kind of star cluster is the globular cluster whose distribution is within a sphere centered on the center of the Milky Way galaxy.
This star cluster, Coma Berenices, is near the north galactic pole, as far as you can get from the milky band. This bright star cluster is not a Messier object, but it is a constellation. We'll talk about Messier objects a bit later. Coma Berenices translated to English is Berenice's hair. The stars of the cluster seem to form lines extending from the top star, that do look like strands of hair.
According to legend Berenice was queen of Egypt. Her husband King Ptolemy went off to war. She was known for her golden tresses. As a sacrifice to the goddess Aphrodite for the king's safe return, she cut off her hair and presented to the goddess's temple. Later the king did return safe and sound. It was then that someone noticed that the tresses that had lain in the temple had disappeared. Asked where they had gone, the oracle of the temple pointed skyward. The gods were so touched by the queen's sacrifice they placed her golden tresses in the sky.
The reason Coma Berenices can be situated near the galactic pole and still be within the galactic disk is because it's close to us, only about 250 light years away. There are less than 40 stars known to be members of the cluster.
There are other wonderful objects visible in telescopes in and around Coma Berenices. The galaxy NGC 4565 is a beautiful edge-on spiral. It looks like a thin spindle of light. M53 is a beautiful globular star cluster. The brightest stars in it can be resolved in a telescope as small as 6 inches in diameter. Charles Messier came across M53 226 years ago. He was interested in discovering comets, so when he found that it didn't move, it couldn't be a comet, and so listed it as an object known not to be a comet, number 53 in his list. Messier's list of non-comets has come down as some of the brightest and most beautiful deep sky objects visible.
Speaking of globular star clusters, M3 is the brightest of the early spring globulars. It is located a bit more than a third of the way between the stars Arcturus and Cor Caroli. It is resolvable with an eleven inch telescope. It's a wonderful prelude to the Great Hercules Cluster M13 visible later in the evening and later in spring.
Looking to the Big Dipper, the hind end of Ursa Major, the Great Bear, we find it the realm of many galaxies. Off the end of the handle of the dipper, and officially within the boundaries of Canes Venatici the Hunting Dogs, is M51, the Whirlpool Galaxy. This galaxy and its companion, linked by a distorted spiral arm is perhaps the easiest to discern the spirals. You need a large telescope, and you've got to believe.
M101, not far away, is large and faint. The trick is spotting it at all. M81 and M82 in front of the bowl of the dipper are bright galaxies. M81 has a beautiful spiral structure, at least in photographs; while M82 is something of a mystery. It seems at some time in the past a huge explosion tore through the nucleus of this possibly spiral galaxy. Besides light it radiates copious amounts of radio energy.
We finish with M97, a planetary nebula, also known as the Owl Nebula because the circular nebula has two dark circles within it that look like large owl eyes. Seeing the dark eyes is difficult. The galaxy M108 lies nearby and is a rather thin ellipse, helping the observer distinguish one from the other.
So even though we're looking out the thin side of our galaxy, there are plenty of wonders to see with the unaided eye, and with the telescope.
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