This is the Dudley Observatory Skywatch Line for Wednesday, May 30th, and Thursday, May 31st, written by Louis Suarato.
Civil Twilight, when the Sun’s center is 6 degrees below the horizon, occurs around 9 p.m. in our region. This twilight phase reveals the two brightest planets, Jupiter and Venus. Look about 25 degrees over the southeastern horizon for Jupiter, shining at magnitude -2.47. Jupiter’s moon Io, begins to cross in front of the planet at 10:37 p.m., Wednesday. The shadow of Jupiter’s moon Io begins to transit the gas giant at 11:07 p.m., Wednesday. Io and its shadow cross the solar system’s largest planet until Io’s transit ends at 12:46 a.m., Thursday. Io’s shadow transit ends at 1:17 a.m., Thursday. Brighter Venus, blazing at magnitude -3.98, can be found about 20 degrees over the west-northwestern horizon as twilight begins. Venus, the solar system’s hottest planet, is 80.5% illuminated. If you star hop from Jupiter to Venus, the first bright star you’ll come across is Spica. Further west is Leo’s brightest star, Regulus. Between Regulus and the Gemini twins, Castor and Pollux, is M44, the Beehive cluster.
The 98% illuminated, waning gibbous Moon, rises at 9:27 p.m., in the constellation Ophiuchus. The bright Moon overwhelms star clusters M23, and M24, 3 degrees to its east. Asteroid 4 Vesta is located between the two star clusters. With a diameter of 326 miles, Vesta is the second only to Ceres in size of asteroid belt objects. Discovered by astronomer Heinrich Wilhelm Olbers on March 29, 1807, Vesta is the brightest asteroid visible from Earth. Saturn, three days past opposition and shining at magnitude 0.16, , rises in Sagittarius an hour after moonrise. Thursday night, the Moon passes 1.6 degrees north of Saturn. Look through binoculars to see both in the same field of view. Look two degrees below Saturn for globular cluster M22. Mars rises 23 minutes after midnight in Capricornus. Mars shines at magnitude -1.22. By July 27th, when Mars reaches opposition, its brightness will increase to -2.78.