Our night skies are transitioning from Spring to Summer in late May to early June, and you can see two, clear signs of that transition.
The first sign is that Spring, specifically late May and June, is the perfect time to observe globular clusters. Globular clusters are the mysterious giant balls of stars (usually between 100,000 and 1,000,000 stars) that orbit our Milky Way galaxy (and other galaxies) in highly elliptical orbits well outside the galactic disk where most of the galaxy’s stars orbit. Astronomers estimate that there may be 150-200 of these globular clusters orbiting our Milky Way galaxy, and that at least some of these “globulars” may be the cores of smaller galaxies that formed in the early universe even before our own Milky Way and were absorbed by our galaxy later in its development. This could explain why many of these globular clusters contain stars that are 12-13.7 billion years old. M5 is a beautiful binocular and naked-eye globular cluster in the constellation Serpens Caput (the Serpent), and it contains at least 800,000 stars. The constellation Serpens Caput is located in the southeast and is just south of the constellation Hercules. M5 is located south of the head of the serpent (formed by three stars) and will first appear in your binoculars as a condensed fuzzball. The well-known visual astronomer, Stephan James O’Meara, claims that you may even see some color (straw in the middle and blue on the fringes) in M5. Next, the Great Hercules Cluster, M13, is located in the center (known as the keystone) of the constellation Hercules about 2/3rd of the way between the two corner stars of the keystone that form its western side (closest to the northwest corner). In early June, the Hercules constellation is still slightly east of the zenith at 11:00 pm. If you are interested in observing some additional globular clusters be sure to look for M10 and M12 in the nearby constellation Ophiuchus — located east of Serpens Caput.
The second sign is that Vega is rising in the east, and this is a sign of Summer coming because Vega is one of the corner stars of the Summer Triangle (Deneb in the constellation Cygnus and Altair in the constellation Aquila are the other two corners). Vega is the brightest star in the constellation Lyra, a small constellation immediately northeast of the Hercules constellation. While you are observing near Vega, you should search for the fading comet 41P/Tuttle-Giacobini-Kresak (known as Comet TGK). The comet passed by Vega in early May and is now passing through the constellations Hercules and Ophiuchus in June. You can refer to precise star charts for this comet by searching for 41P/Tuttle-Giacobini-Kresak on Google.
Jupiter continues to dominate the evenings in May and June as it shines at magnitude -2.0 (slightly dimmer in June than in May) just west of the star Spica. Spica is the brightest star in the constellation Virgo and it is best found by following the arc of the handle of the Big Dipper (“arc to Arcturus and speed on to Spica”). Jupiter will set at 3:00 am in early June and 1:00 am at the end of June. Be sure to observe Jupiter’s Galilean moons and its highly visible red spot. Saturn rises around sunset and is visible almost all night in June. Saturn is at its largest and brightest in June (near magnitude 0.0), and its rings are very close to their maximum tilt from our line of sight. Venus rises in the east about 1¾ hours before the Sun in early June and 2 hours before the Sun in late June.
Finally, let’s take a quick binocular look at an asterism (a group of stars that seem to form a shape to us but are otherwise unrelated in space or gravitationally). Polaris, the North Star, is easily located as the tip of the handle of the Little Dipper. Polaris is also the diamond in an asterism named the Engagement Ring. There are nine stars visible in binoculars that form a jagged band of stars with Polaris as the diamond.
If you are interested in learning more about what you can see in the night sky right now, visit www.astronomy.com and click on “The Sky This Week” under the Observing tab.