This is Dudley Observatory’s Skywatch Line for Friday, May 4 through Sunday, May 6, written by Sam Salem.
On Friday, the Sun rises at 5:46am and sets at 8:00pm; the waning gibbous Moon sets at 9:08am. As dawn begins on Saturday morning, the waning gibbous Moon shines between Saturn and Mars. Saturn resides to the Moon’s right, and Mars is to the Moon’s lower left. The Moon is 3 degrees north of Mars on Sunday morning.
Venus shines opposite of Jupiter at evening dusk. It sets beneath the western horizon around 10:30pm. Meanwhile, Jupiter is out all night long, from dusk till dawn. Venus gleams at a magnitude –3.9 in the west-northwest at dusk. As twilight fades, see Venus set among the bright winter stars. Jupiter, at magnitude -2.5, rises as darkness falls, and sits due south around sunrise. Jupiter’s Great Red Spot crosses the planet’s central meridian around 11:56 pm on Saturday.
Mars and Saturn gradually reach the meridian before dawn. Saturn shines at magnitude 0.3. The nearby Mars glows at magnitude –0.4. Saturn rises around midnight. Mars rises around 1:20am. Saturn is 1.6 degrees north of M22 this week. Use Saturn to locate M22. Messier 22, also known NGC 6656, is an elliptical globular cluster in the constellation Sagittarius, near the Galactic bulge region. M22 is one of the brightest globulars in the night sky. Its brightest stars are 11th magnitude, with hundreds of stars bright enough to resolve with an 8″ telescope.
On Sunday, the Eta Aquariid meteor shower reaches its peak in the predawn hours. This shower particularly favors the Southern Hemisphere. For our area, the shower’s radiant doesn’t rise very high above the southeast horizon before the morning twilight. And the light from a waning gibbous Moon will wash out all but the brighter streaks. Saturday could be the better morning to watch the meteor shower, as the Moon will set at an earlier hour than it will on Sunday morning. You don’t have to locate the radiant to watch the meteor shower. The Eta Aquariid meteors streak all over the sky, but they appear to radiate from the Y-shaped group of stars called the Water Jar. The Water Jar is part of the constellation Aquarius. That’s how the meteor shower got its name.
The Summer Triangle is beginning to make its appearance in the east. The first in view is Vega, shining low in the northeast as twilight fades away. Next up is Deneb, lower left of Vega by two or three fists at arm’s length. Deneb takes about an hour to appear after Vega does. The third is Altair, which shows up far to their lower right by midnight. One other signal that summer is just around the corner is the return of bright globular clusters to the evening sky. As darkness arrives, M3 is in prime position nearly overhead. M3 resides in the constellation Canes Venatici. The easiest way to locate M3 is to draw an imaginary line connecting Arcturus and third-magnitude Cor Caroli. Locate Arcturus, the brightest star in constellation Boötes. Then locate Cor Caroli, the brightest star in constellation Canes Venatici. M3 is situated slightly less than half way from Arcturus to Cor Caroli. The cluster is an easy catch in binoculars. Small telescopes used at moderate magnification will start to resolve individual cluster members.
Sunday marks the 146th birthday of the Dutch astronomer and cosmologist, Willem de Sitter. He is best known for his contributions to cosmology. Willem de Sitter developed theoretical models of the universe based on Albert Einstein’s general theory of relativity. His 1917 solution to Albert Einstein’s field equations showed that a near-empty universe would expand. Later, he and Einstein found an expanding universe solution without space curvature. de Sitter re-determined the fundamental constants of astronomy and determined the variation of the rotation of the earth.