Astronomy: The Week Ahead – Mon 18 May thru Sat 23 May

MilkyWay in Mountains


Monday May 18

The constellation Bootes, The Herdsman, is well up in the east now, an hour after sunset. It is very recognizable by its kite shape, and the bright star Arcturus, anchoring its southern vertex.

This is an ancient constellation, and one of the Greek astronomer Ptolemy’s original 48 constellations. Its roots are in Greek mythology, telling the tragic story of Icarius, the grape farmer, his daughter Erigone, and winemaking. The daughter is remembered as Virgo, and Icarius’ dog, Canis Major or Minor.


Tuesday May 19

The star Izar, also known as Epsilon Bootes, is a fine tight double, which may be split into its two components in a three-inch or larger telescope. The primary component shines at magnitude 2.37, easily visible with the unaided eye. Its companion sits 2.8 arcseconds away, and is magnitude 5.12. They have a 1,000 year orbital period, around their barycenter, and sit 203 light years from our eyes.


Wednesday May 20

The Fall constellations Pegasus and Andromeda are rising over the eastern horizon in the predawn skies. A great sight in a pair of binoculars is M31, also known as the Great Andromeda Galaxy. Grab your binos for a nice view of this very large close neighbor of ours. Its extent, seen in a dark sky, spans over three Full Moons. Your view will be of a large oval haze. Find the Square shape of Pegasus, then follow the arcing chain of stars to Beta Andromeda, and move slightly upward past the dimmer star in the upper chain of stars. M31 should be pretty obvious.


Thursday May 21

Tonight, let’s do some astronomy with just our unaided eyes. The western skies an hour after sunset features three solar system objects. Jupiter is highest up, and brilliant Venus lower to its right midway in the constellation Gemini, which seems to stand upright, heading toward sunset. To Venus’ left, a four-day-old waxing crescent Moon is visible. Surrounding these objects are some of the brightest stars in the sky. Regulus by Jupiter, in Leo, Castor and Pollux above Venus, Capella to its right in Auriga, and Procyon, near the Moon in Canis Minor. Go enjoy this rich view as twilight fades to night.


Friday May 22

Saturn is at opposition tonight. In the image at left we show a flat featureless horizon, showing the planet just visible at sunset. It will remain visible in the sky until sunrise. This is called opposition, as Saturn is directly opposite the Sun from Earth. Watch it rise, in the zodiacal constellation Libra, and below Virgo. Saturn’s rings are nicely inclined, and will be a pretty view in any size telescope. Tonight, it is 8.9667 Astronomical Units from Earth (an Astronomical Unit is the average distance between earth and the sun – 93,000,000 miles).


Saturday May 23

The great globular cluster M2 (Messier 2) is often overlooked due to a lack of bright landmark stars nearby. But it is easily visible in binoculars, about midpoint between Altair in Aquila, and Fomalhaut, in Pisces Austrinus. The Alpha (A) and Beta (B) stars of Aquarius, though not first magnitude, are easy to find, and serve as jumping off markers to this big cluster.

M2 is just beyond average naked-eye threshold, at magnitude 6.47. It is easily visible in binoculars, and resolves into hundreds of stars in a telescope. Its distance is about 37,000 light years.

Happy viewing!