April is the last month to see the full set of brilliant winter stars which now fill the western evening sky. Dazzling Orion is in the southwest at dusk. His three-starred belt is halfway between reddish Betelgeuse and bluish Rigel. Orion’s belt points rightward to Aldebaran in Taurus the Bull. To Orion’s upper left are the twin stars Castor and Pollux, marking the heads of Gemini, the Twins. You can find Sirius, the brightest star we ever see at night, by drawing a line from Orion’s belt towards the left. Forming a triangle with Sirius and Betelgeuse is Procyon, the Little Dog Star.
Joining the winter stars are stars of spring rising in the east. Ursa Major, the Great Bear, which includes the Big Dipper, is high above the North Star on spring evenings. Extend the Big Dipper’s handle to ‘Arc to Arcturus’ and then ‘speed on to Spica’. Look for Leo, the Lion high in the sky at dusk. There are fewer bright stars in this direction because of where the plane of our galaxy is in the sky. The area of sky between Gemini and Taurus and over Orion’s head is the galactic anticenter, which means that we face directly away from the galactic center when we look in this direction. Those bright winter stars setting in the west are the stars in our galactic arm, right behind the Sun. On the other hand, if you look at the sky between Ursa Major, Leo, Virgo, and Bootes, you’re looking straight up out of the galactic plane, towards the galactic pole. There are fewer stars in this direction.
Venus is in the west at dusk this month. Look for it low to the horizon, over the point of sunset. Venus outshines everything in the sky but the Sun and Moon, so you can look for it even in twilight. Venus remains the evening star all spring and summer.
Jupiter is now a late evening object. Look for it low in the southeast by 10:40 pm tonight (April 2). By the 30th, Jupiter rises at 8:30, which is during evening twilight. On May 8, Jupiter is up literally all night long.
Mars is within 1.5 degrees of Saturn on April 2, then pulls away from it during April and May. Slightly brighter than Saturn now, Mars will brighten much more as it approaches opposition in July. Both planets are in the south at dawn.
Moon Phases in April 2018:
Last Quarter: Apr. 8, 2:18 a.m. New: Apr. 15, 8:57 p.m.
1st Quarter: Apr. 22, 4:46 p.m. Full: Apr. 30, 7:58 p.m.;
George Observatory is open to the public once again! Come join us any clear Saturday night.