Bootes the Herdsman is well placed for viewing during early evening hours in late May. He keeps two dogs which represent the neighboring constellation Canes Venatici. Credit: Urania’s Mirror
Some constellation names are easy to pronounce at first sight like Leo, Hydra and Cygnus but then there’s Bootes. On first encountering the word as a young teen, I still remember calling it ‘booties’. That’s what it looks like after all. ‘Boots’ is another variation I’ve heard many times since. And yet somehow you know the ancients wouldn’t have created a cultural myth based on a pair of galoshes.
It’s really pronounced ‘Boe-OH-teez’ and represents a herdsman. The word’s origin isn’t certain but it may come from the Greek word for ‘noisy’ and refer to the herdman’s shouts to his animals. Or it might be rooted in the ancient Greek word for ‘ox driver’. The nearby constellation of Ursa Major (the Great Bear) was sometimes depicted as a cart pulled by oxen.
The cone-shaped constellation Bootes extends north of the bright star Arcturus, an orange giant star 37 light years from Earth. This map shows the sky facing south around 10 p.m. in late May. Maps created with Stellarium
In the 21st century I’ll often refer to it as the ‘ice cream cone constellation’ because Bootes’ outline resembles a sugar cone topped by a single scoop. Whatever it is, it’s not hard to see, because the group contains the fourth brightest star in the sky, Arcturus.
Face south at nightfall and you’ll see two bright ‘stars’ halfway up in the southern sky. Those are Saturn and Spica and they’re separated by one fist held at arm’s length. Now tip your head back and gaze off high and to their left to spy aÂ brilliant orange-pink star. That’s Arcturus, a Greek word for ‘bear guard’. If you’re crazy enough to tip your head even further back and risk falling over, you’ll understand the name’s origin. Arcturus follows the Big Dipper, part of the Great Bear, which is nearly overhead.
Arcturus forms a large, temporary figure in the late spring-early summer sky sometimes referred to as the Spring Triangle. The ice cream cone part of Bootes is composed of a handful of stars extending two fists to the north or above Arcturus. Two little ‘antennae’ poke out on either side of the brilliant star to complete the constellation’s outline. That wasn’t too hard, was it?
M3 forms a right triangle with Arcturus and the star Eta or a nice equilateral triangle with Arcturus and Rho. The cluster is about two binocular fields of view away from Arcturus. Both M3 and the marked star are 6th magnitude. Stars are shown to magnitude 7.5.
Next we’ll use your new-found knowledge of Bootes to visit one of spring’s most outstanding star clusters, the globular cluster M3 in nearby Canes Venatici. For this you’ll need a pair of binoculars – even small ones will do. Once your eyes are adapted to the darkness, point your binoculars at Arcturus and the fainter star Eta Bootis to its right. The cluster is about two binocular fields of view directly above Eta and forms a right triangle with Eta and Arcturus.
M3 will look like a bright, ‘fuzzy’ star right next to a similarly-bright but real star. It’s most convenient the two are next door to each other because the star helps us tell the two apart.
M3 shows its true colors as one the sky’s finest globular star clusters in this photo made with a 32″ telescope. It’s 33,900 light years away and 180 light years across. Globular clusters are rich, spherical collections of stars in the outer halo of our Milky Way galaxy that revolve around the galaxy’s core. Credit: Jim Misti
“Magnificent” will probably not be the first word to pop out of your mouth upon seeing M3, but we are using binoculars after all. In truth, there are a half million stars packed into that tiny undistinguished spot. To get a sense of this cluster’s true beauty, a modest 6-inch telescope and dark skies are required. They you’ll begin to tease out dozens upon dozens of tiny stellar points winking like fireflies around M3′s radiant core. Larger scopes provide a most impressive view that will keep an observer glued to the eyepiece for many minutes.
M3 was discovered by Charles Messier on May 3, 1764 and added to his catalog – the Messier catalog – of fuzzy objects not to be confused with his favorite quarry, comets.
There are two main types of clusters in our sky – the wider, spread-out variety like the Seven Sisters (Pleiades) called open clusters and the densely-packed, spherical globular clusters. Open clusters populate the Milky Way’s spiral arms and are generally much younger than the globulars, which occupy a great halo of space around the center of galaxy. They’re the mighty ancients of the universe with ages of 10 to 12 billion years. In contrast, most open clusters break apart into individual stars after several 100 million years.
When you look at M3, whether by telescope or binoculars, it’s hard to imagine its size and star density. 500,000 stars gathered into a sphere that spans five times the distance between Earth and the star Arcturus. Just think of that. What human imagination could have ever conceived of the wonder that nature rolls out with casual ease on warm May evenings.