Northern Sky: May 12 - 25

Northern Sky -  by Deane Morrison - May 12-25 2018
 
 
For a week starting Saturday, May 12, we have morning and evening skies that are free or nearly free of moonlight, and that makes for good starwatching. The moon becomes new in the early morning of the 15th, then starts its next march eastward across the evening sky. As it goes, it gets bigger and brighter and sets later, so we have less and less time to see celestial objects without the moon washing everything out.
 
On evenings around new moon, look for Leo, the lion, high in the southwest. Its most prominent feature is a backward question mark of stars, known as the Sickle. The dot of the question mark is Regulus, the brightest star in Leo. Regulus is also the sharp point of a stellar triangle; the other two stars are brilliant Arcturus, which is high in the south at nightfall, and Spica, which is below Arcturus. Arcturus is the anchor for the kite-shaped constellation Bootes, the herdsman, and Spica is the only bright star in Virgo. These days Spica and Arcturus are also part of another triangle, with Jupiter. Jupiter is a beacon in the east, near the peak of its brightness. Also, just to the southwest of Spica you’ll find a four-sided figure. This is Corvus, the crow—another of those constellations that aren’t very prominent but can be fun to find.
 
On Wednesday, the 16th, look for a very young crescent moon down by the horizon below Venus—that brilliant light in the west. The next night, the 17th, the waxing moon will have moved to about the same level as Venus. On the 18th, a fatter crescent appears below Pollux, the brighter of the Gemini twins. The other twin, Castor, is to the right of Pollux. On Monday the 21st, a first-quarter moon will be practically sitting on top of Regulus. And the evening of the 25th, a bigger, brighter moon appears above Spica.
 
If you have a lawn chair, you may want to grab it and look for Ursa Major, the great bear. It’s really high after nightfall these days, close to the overhead position, hence the advisability of observing from a reclining position. You may also need a star chart to make out the whole constellation. The Big Dipper is the bear’s hindquarters and tail, and the arc of the tail—which is also the handle of the dipper—leads you to Arcturus. Just remember “arc to Arcturus.” At the bend of the handle is a famous double star. Binoculars will bring them out nicely. The stars are Mizar, the brighter one, and Alcor, its fainter companion. These two have also been dubbed the horse and rider.
 
Also, I enjoy looking for three tight pairs of stars that represent the paws and one hind foot of the great bear—although not all star maps indicate that. The three pairs of stars form a diagonal line below the bowl of the Big Dipper and they have been named the Three Leaps of the Gazelle. They’re also not prominent, but they’re one—or three—more things that can be fun to find.
 
In astronomy news, NASA just launched its InSight mission to Mars. InSight is designed to find out, as NASA puts it, “what makes Mars tick.” The lander will plant a seismometer on Mars. It’ll study Mars quakes, and the mission will also track how heat in the interior of the planet gets dispersed, and how Mars wobbles. It may even be able to detect liquid water or plumes of active volcanoes below the Martian surface. All this data will shed light on the formation of other rocky planets, including Earth and the moon. Landing is scheduled for November 26th.