This is Dudley Observatory’s Skywatch Line for Friday, May 25 through Sunday, May 27, written by Sam Salem.
On Friday, the Sun rises at 5:24am and sets at 8:22pm; the waxing gibbous Moon rises at 4:20pm and sets at 3:37am; the waxing gibbous Moon passes almost 7 degrees north of the bright star Spica, the brightest star in the constellation Virgo the Maiden. On Sunday, the waxing gibbous Moon and Jupiter rise together, separated by less than 5 degrees.
As twilight fades, watch Venus, at magnitude –3.9, low in the west. It remains visible until around 11pm. Meanwhile, in the southeast, Jupiter is beaming away at magnitude –2.5. Jupiter is only 1½ degrees east of the 2.7-magnitude Alpha Librae, also known as Zubenelgenubi, in constellation Libra. Zubenelgenubi is a double star. Zubenelgenubi is an Arabic name indicating that this star was once perceived as the Southern Claw of the neighboring constellation Scorpius the Scorpion. Watch Mars and Saturn one hour before sunrise. Saturn shines at magnitude 0.1, while Mars is considerably brighter at magnitude –1.3.
Observing the Moon, the planets, or bright double stars are the options for this weekend’s moonlit nights. Use a small telescope to locate the trio of double stars in the constellation Boötes, the Herdsman. Start with Xi (ξ) Boötis. You’ll have no trouble locating this nicely colored binary. It sits 8.5 degrees due east of Arcturus. The primary shines at magnitude 4.7 and the secondary at magnitude 7.0.
The second double star is 44 Boötis. You’ll find it in the far northern part of the constellation, 7.3 degrees due north of Nekkar. The brighter of the two stars shines at magnitude 5.3 and its companion is at magnitude 6.2. With a separation of only 1.6″, these two stars will test the limits of 3-inch telescopes. Because of the closeness of the main stars, you’ll need to crank the magnification to split the pair. The primary and secondary stars are yellow-white and yellow-orange, respectively.
The third double star is the easiest to find and to split. It’s Delta (δ) Boötis. The primary star shines at magnitude 3.5 and the secondary glows at magnitude 8.7. Although these magnitudes represent a brightness difference of 120, the 105 arc second separation between the pair makes seeing the fainter star easier. Although you can separate this wide binary through binoculars, use a telescope at a magnification around 50x to bring out the stars’ colors. The primary star is yellow, while the secondary star shines white, or perhaps yellow-white.
Sunday marks the 64th birthday of the American theoretical physicist and cosmologist Lawrence Maxwell Krauss. Krauss was among the first physicists to propose the enigmatic dark energy that makes up most of the mass and energy in the universe. Krauss became the inaugural director of the Origins Project at Arizona State University in August 2008. This is a trans-disciplinary initiative with a mission to explore fundamental questions ranging broadly from the origins of the universe to life, and to broaden public understanding of science issues. He has written a number of science books for the layman.