As darkness falls on May 28 and 29, 2015, look for the bright waxing gibbous moon to shine close to Spica, the brightest star in the constellation Virgo the Maiden.
Practiced stargazers often refer to Spica because it’s a bright star of the Zodiac. The constellations of the Zodiac make up the rather narrow band of the starry sky through which the sun, moon and planets all travel. Thus the moon passes Spica every month, and planets routinely appear near Spica as well. One year ago, in fact – in May 2014 – Mars shone quite close to Spica on the sky’s dome. At present, however, Mars is lost in the sunset glare.
As darkness falls on these May and June 2015 evenings, note two other bright star-like points of light near the southeast horizon: the planet Saturn and Antares, the brightest star in the constellation Scorpius the Scorpion. Like Spica, Antares is a bright star of the Zodiac. The moon passes close to Antares once a month, and the planets pass by Antares in predictable cycles. This year, in 2015, the golden planet Saturn shines close to the ruddy star Antares throughout the year.
The ecliptic on the above sky chart highlights the sun’s annual path through the constellations of the Zodiac. The supposed movement of the sun in front of the backdrop stars, though, is really an illusion, a sleight of hand that fooled many (but not all) ancient astronomers. Modern astronomy now knows the sun’s apparent motion upon the ecliptic is really a reflection our planet Earth revolving around the sun.
The moon and planets are always found on or near the ecliptic – Earth’s orbital plane projected onto the stellar sphere. Practiced stargazers use the ecliptic to find the planets, and you, too, can use key zodiacal stars – such as Spica and Antares – to make out the ecliptic with the mind’s-eye. At present, Saturn shines in front of the constellation Libra, very close to the border of the constellation Scorpius. (On a moonless night, you might even be able to spot the star Zubenelgenubi, Libra’s alpha star, in between Spica and Antares.)
Saturn will stay in front of the constellation Libra until October 2015, at which juncture the ringed planet will cross over into the constellation Scorpius.
The moon moves much more rapidly than the planets do through the constellations of the Zodiac. In fact, the moon will pair up with Saturn in just a few more days.
Bottom line: As darkness falls on May 28 and 29, 2015, look for the bright waxing gibbous moon to shine close to Spica, the brightest star in the constellation Virgo the Maiden.