This Week’s Sky at a Glance, June 9 – 16 ~by Curt Nason
Globular clusters are among the oldest and largest objects associated with our galaxy, being about 12 billion years old and containing tens to hundreds of thousands of stars packed into a compact sphere. There are more than 150 globulars orbiting in the halo of the Milky Way galaxy, and many more are known to be orbiting larger galaxies like M31 in Andromeda. Many can be seen in binoculars as a fuzzy patch of light, perhaps resembling those little white patches you see below bird feeders. A good sized telescope is able to resolve some of their stars. The larger globulars seen from a dark location have been described as granules of sugar against black velvet.
Summer is the season for observing globular clusters. M4 is just to the right of Antares in the constellation Scorpius and it is one of the closest to us at 7000 light years. M13 in the Keystone of Hercules is relatively close at 22,000 light years. One that would outshine M13 if it were higher in our sky is M22, just left of the lid of the Teapot in Sagittarius. Another easy target is M3, located halfway between Arcturus and Cor Caroli, the brightest star in the small constellation Canes Venatici below the handle of the Big Dipper. Two other standouts are M92 in Hercules and M5 in Serpens. From a dark sky, many dimmer globulars can be picked out in the region of Sagittarius and Ophiuchus.
The concentration of globular clusters in this region of sky is not by accident, and it played a role in another lesson of humility for humanity. Harvard’s Harlow Shapley studied globular clusters a century ago and noticed that most were located around Sagittarius. If they were evenly distributed around the core of our galaxy, as believed, then the centre of the galaxy must lie in that direction. Just as Copernicus and Galileo demoted Earth from the centre of the solar system, Shapley showed that the Sun was not at the centre of the Milky Way.
This Week in the Solar System
Saturday’s sunrise in Moncton is at 5:28 am and sunset will occur at 9:09 pm, giving 15 hours, 41 minutes of daylight (5:36 am and 9:10 pm in Saint John). Next Saturday the Sun will rise at 5:27 am and set at 9:12 pm, giving 15 hours, 45 minutes of daylight (5:33 am and 9:14 pm in Saint John).
The Moon is new on Wednesday and, if you can spot it around 10 am on June 16, look for Venus within a binocular field above it. If you are successful with that, try for Venus without the binoculars. Jupiter is at its best for observing around 11 pm, and with a telescope you might see its Red Spot around 10 pm on Wednesday and midnight on Friday. Saturn rises around 10 pm above the lid of the Sagittarius Teapot. Mars continues to brighten in the morning sky; it will be the main attraction for observers this summer.
The William Brydone Jack Astronomy Club meets in the UNB Forestry / Earth Sciences building in Fredericton on Tuesday at 7 pm. All are welcome. The first RASC NB star party of the year takes place at Kouchibouguac National Park on June 15-16.
Questions? Contact Curt Nason.