Leo the Lion is mostly a constellation of late winter and spring. But he's not gone yet. As twilight ends look due west, somewhat low, for Regulus, his brightest and now lowest star: the forefoot of the Lion stick figure. The Sickle of Leo extends upper right from Regulus. The rest of the Lion's constellation figure extends for almost three fists to the upper left, to his tail star Denebola, the highest. He'll soon be treading away into the sunset.
As we count down the days to official summer (the solstice is June 20th), the big Summer Triangle shines high and proud in the east after dark. Its top star is bright Vega. Deneb is the brightest star to Vega's lower left. Look for Altair farther to Vega's lower right.
FRIDAY, JUNE 5 ■ Catch Mercury in twilight! It's under Pollux and Castor this week, as shown below. Mercury is ending its last good evening showing until winter 2021. Mercury is still visible in the western twilight, under the heads of Gemini, but it's fading. This scene is drawn for…
Bright Capella is still up in the northwest in twilight, but it sets in the northwest fairly soon after dark. That leaves Vega and Arcturus as the brightest two stars in the evening sky. Both are magnitude 0. Vega shines in the east-northeast. Arcturus is very high toward the south.
Venus is a super-thin crescent as it plunges down to the sunset horizon this week. Bring out the telescope and/or binoculars. Mercury, also in the western evening twilight, is a tiny "half Moon" with a much less intense surface brightness.
Look high in the west for Pollux and Castor, the heads of the Gemini twins. They form the top of the enormous Arch of Spring. To their lower left is Procyon, the left end of the Arch. Farther to their lower right is brilliant Capella.
Venus continues to shine high in the west at nightfall for many weeks on end. But as the season advances, its starry background slides toward the lower right behind it. For instance not long ago the Pleiades were very high above it, but as of this evening they're 20° apart.
Venus shines near the Moon and Betelgeuse is brightening again — find other night sky sights in this week's roundup.