This week seems to have a few showers and thunderstorms (very cloudy skies) ahead, but despite this, there will be some clear (or at least partially clear) nights. The nightly low temperature hovers around 60°F and will provide a nice comfortably cool temperature for both you and your stargazing gear. Sunset this week will be passing 8:50 PM meaning the first stars will appear around 9:20 PM and fainter stars will be visible by 9:50 PM. This week be on the lookout for globular clusters, Mercury and Venus passing each other, Antares the star, and the 2.5 month-old Nova Cassiopeiae.

As summer approaches in the northern hemisphere, the arms of the Milky Way get higher in the sky at night. Since most stars and nebulae sit within the plane of the Milky Way, or the arms of the Milky Way, lots of star clusters become visible (in addition to other deep-sky objects). Arguably more interesting, however, are globular star clusters. These ultra-dense gatherings of old stars sit far out in the halo of the Milky Way and are not highly concentrated in the plane of the galaxy. Despite looking like faint fuzz balls through a telescope, globular clusters may contain 30,000 stars, and some upwards of a million.

Messier object 13 (M13), also known as the Hercules Globular Cluster, is one of the more famous globulars and it can be seen with a pair of binoculars looking 45° above the eastern horizon after sunset.

The positions our our Milky Way’s globular clusters. Notice how they collect near the bright center of the galaxy.

Starting Friday the 28th, right after sunset use binoculars or a telescope to spot Venus low in the west. You may notice that no more than 0.5° away is Mercury. Close encounters like these with the inner planets is a little more common than Jupiter-Saturn conjunctions since they orbit around the sun faster and have more opportunities to overlap.

Venus as seen on May 28. The pair will remain close for a few days after that.

At 9:30 PM any time this week, look low on the southeast horizon to find a bright red star – this is Antares. Around 11 PM or so when Antares is more overhead use binoculars to spot some neighboring young blue stars. If you are an astrophotographer, Antares is part of the Rho Ophiuchi cloud complex. This is a very wide-field object that is a beautiful arrangement of stars, gas, and dust. The red Antares and blue neighboring stars give great popping colors and there is a long tail of dust and gas almost resembling a massive shooting star.

Antares, and the colorful Rho Ophiuchi region. The colors can be seen in photographs, but are too faint to be made out with the eye at a telescope.

In March, a new nova in Cassiopeia made some astronomy headlines. For some time, it shined at magnitude 7.7 making it visible with binoculars and telescopes. In early May this nova rapidly flared up in brightness and shined at magnitude 5.4 making it a naked-eye object. It has since dimmed back to its original magnitude 7.7. You can find this nova by hopping equidistant and in the same direction from the two stars on the “steep” side of the Cassiopeia constellation. This nova also sits very near to the famous Bubble Nebula.

Enjoy the clear nights scattered between thunderstorms this week. The cool temperatures will be great for laying out a blanket or a lawn chair to stare upwards into the cosmos. Try to visit a dark sky park to truly experience the night sky especially now since the Milky Way core is higher in the sky. Look this week for some globular clusters, the close conjunction between Mercury and Venus, Antares and the Rho Ophiuchi complex, as well as the two-month-old nova in Cassiopeia.

Clear Skies!

Jared May: What's up the Last Week of May