Venus, the brilliant evening “star” in the west at dusk in June, brightens nearly to its peak while closing in on faint Mars and Regulus. Golden Arcturus, high is south at dusk, is the brightest actual star currently visible at nighttime. The Summer Triangle in the east and Antares in the southeast announce the imminent arrival of the Milky Way. Jupiter dominates the predawn.
The June 2023 Sky Calendar illustrates many of the events described in this column. It, together with a constellation map for the month’s evening sky, is available by subscription at www.abramsplanetarium.org/skycalendar.
Evenings: Venus reaches a maximum of 45° to the upper left of the setting Sun on June 3, and brightens from magnitude -4.4 to -4.7 during June. On June 1, Venus is 68 million miles from Earth. Through a telescope, it then displays a disk 23” (arc seconds) across and half illuminated. On June 30, Venus is 46 million miles from our planet and shows a disk 34” across and one-third full. The crescent becomes large enough to detect even with binoculars, if observed in daylight or bright twilight, before the contrast of Venus against a darkening sky becomes too great. Seen from Reno, Venus on June 1 is 36° up at sunset, and sets 3.3 hours after the sun. On June 30, though Venus is still nearly 42° from the sun, it’s only 26° up in the west at sunset, and sets 2.3 hours after sunset.
Watch Venus close in on Mars! On June 1, Venus is 5.2° to the left of Pollux, and aligns with the Twins, Pollux and Castor, 4.5° apart. Mars is then 10.5° to the upper left of Venus. Binoculars show stars of the Beehive cluster surrounding Mars that evening and the next. Both planets are moving east against background stars throughout June—Venus by nearly 1°, slowing to about 0.6° per day, and Mars by 0.6° daily. The gap between Venus and Mars shrinks to 8° on June 8, and 7° on June 11. Use binoculars to watch Venus pass north of the Beehive June 12-14. The brilliant planet appears within 5° to the west (lower right) of Mars from June 19-July 10. Least separation of 3.6° occurs on June 30, with Venus still west of Mars. An approach of one planet within 5° of another without overtaking it is called a quasi-conjunction. The planets now begin to spread apart and won’t appear as close again until the latter half of February 2024.
Mornings: Jupiter, of magnitude -2.1 to -2.2 in Aries, is the standout object of dawn, starting low in the east and climbing as the month progresses. Saturn, of magnitude +0.9 to +0.7, begins June in the southeast, and climbs higher toward the south. Saturn begins retrograde on June 17, 4.8° west-southwest of fourth-magnitude Lambda in Aquarius. Around then, the rings are tipped 7.3° from edge-on, the least for this year. On June 19, 2.5 years after their very close pairing in December 2020, Jupiter and Saturn are 60° apart. Mercury has a very poor apparition for northerners, climbing only 2° above the horizon in mid-twilight early in June, as seen from Reno. Using binoculars June 1-17, look 13° to 34° to the lower left of Jupiter. The waning moon at dawn appears near Saturn on June 9 and 10, near Jupiter on the 14th, and near Mercury on the 16th
Moonlight, all night: On the night of June 3-4, the full strawberry moon appears 4° to the lower left of Antares at dusk, and 7° to the upper left of the star at dawn.
The moon returns to the early evening sky on June 18 as a thin, 1 percent crescent, very low in the west-northwest, 34° to the lower right of Venus 30-40 minutes after sunset. It will provide a chance to catch the young moon within 24 hours after new. To succeed, seek out a spot where mountains won’t block your view, and use binoculars.
On following nights, the moon sets later, in a darker sky, and will be easy for unaided eye. On June 19, find the 4 percent moon 22° to the lower right of Venus, and within 3° to 4° to the lower right of Pollux. On June 20, the 9 percent crescent will appear 11° to the lower right of Venus and 9° to the upper left of Pollux.
On June 21, a four-day old, 14 percent moon closely paired within 3° to the upper right of a 39 percent Venus proves that the planet, facing a greater portion of its sunlit hemisphere toward us, must be the more distant object. Note Mars 4.5° to the upper left of Venus, and the star Regulus, heart of Leo, 11° to the upper left of Mars. Later that evening, shortly after 10 p.m., the crescent moon’s southern cusp (the lower point of the crescent) passes just 2.6° to the upper right of Venus.
On the 22nd, the 22 percent crescent moon is 5° to the right of Regulus. Mars and Venus are 7° and 11° to lower right of the moon, respectively.
On June 23, the 30 percent moon has passed all three objects. Regulus, Mars and Venus appear to the moon’s lower right, by 9°, 18° and 22°, respectively.
Continuing its eastward motion through the zodiac, on the 27th at dusk, the 88 percent moon passes within 4° to the upper left of Spica, the spike of grain in the hand of Virgo.
Three nights later, at dusk on June 30, the star Antares appears about 2° to the lower left of a 93 percent moon. Binoculars will be useful for seeing the star deep in the lunar glare, especially later that night, as the moon closes in. Around 2 a.m. on Saturday, July 1, the moon’s southern edge passes just more than a half of a moon’s width north of the star.
When the Summer Triangle of Vega, Deneb and Altair has completely risen by nightfall, and the Scorpion moves into the southern sky, we know that the season for evening viewing of the Milky Way is at hand. On dark, moonless nights, look for the Teapotasterism formed by eight bright stars of Sagittarius, the Archer. It follows Antares and the Scorpion across the southern sky, while the Summer Triangle climbs high in the east. The Milky Way looks like a cloud of steam rising out of the spout of the Teapot, and passing through the Summer Triangle, along the neck of Cygnus, the Swan. As we face the “Great Sagittarius Star Cloud” above the Teapot spout, we’re looking toward the inner regions of our Milky Way, and as we look at the “Cygnus Star Cloud,” we’re looking ahead of the sun, into our own spiral arm, which binoculars readily resolve into many stars!
The Milky Way is in an ideal position for observation in a dark, moonless sky, with the center of our galaxy highest and due south at June 12 at 1:25 a.m., getting four minutes earlier each night, until June 22 at 12:45 a.m.
There are other good viewing times! If you look on earlier dates or times of night, the Milky Way won’t be as high in the sky. Later, the southern parts of the Milky Way will start to descend lower. In July, the ideal viewing times will back into convenient evening hours. Try to avoid moonlight, or areas with bright artificial lights.
Robert C. Victor originated the Abrams Planetarium monthly Sky Calendar in October 1968 and still produces issues occasionally, including May and July 2023. He enjoys being outdoors sharing the beauty of the night sky and other wonders of nature. Robert D. Miller, who provided the evening and morning twilight charts, did graduate work in planetarium science, and later astronomy and computer science at Michigan State University, and remains active in research and public outreach in astronomy.