Planets and bright stars in June
At 5:51 a.m., June 21, our longest day, Summer Solstice officially begins astronomical summer. Earliest sunrise is about a week earlier, latest sunset about a week later. For refreshers on why those don't all occur on June 21, type "earliest summer sunrise" in a search engine.
Mosquitoes and ticks will be abundant soon.
Jupiter dominates the SE evening sky now but by June's end it will set only an hour after Sol. Mercury is barely visible in bright evening twilight in the WNW now but will soon disappear into Sol's glare. It will be between us and Sol on June 19, but not directly. The eight planets' orbits around Sol are not exactly in the same plane, so transects of Sol by Venus and Mercury are exceedingly rare.
Mars is due south at dusk Sunday, but moves west by month's end. It is about as bright as Arcturus in Boötes, almost overhead, but redder. We are leaving it behind, which helps move it eastward through Virgo toward whitish Spica, which it will pass on Bastille Day.
At dusk, Saturn is high in the south. We've passed it in our much faster orbit around Sol, so it is retrograding against the stellar background, making one of those loops in the sky that puzzled ancient geocentric stargazers. Copernicus solved that one, but it was a long time before church and civil authorities bought his heliocentric ideas. Human history is strange.
Venus, our Morgenstern, is a predawn object, due east. A thinning crescent Luna will pass to
its right on June 23-25. Don't wake me.
In addition to Arcturus, bright evening June stars include Regulus in Leo, Spica in Virgo, and
Antares in Scorpius, all three in the zodiac, the 13 constellations in Sol's apparent path against the "fixed" stars, the ecliptic.
The other three brightest stars this month are the "summer triangle," each in its own constellation. The brightest is Vega in Lyra, high in the east. Next is Altair in Aquila, much lower in the east, and Deneb, in Cygnus, between Vega and the NE horizon. Of the three, Deneb is dimmest, about as bright as Regulus. But apparent brightness depends both on intrinsic brightness and distance.
Regulus, some 3.5 times Sol's mass, is a young ordinary star, only a few million years old. It is some 77 light years away. Deneb is a white supergiant, intrinsically one of the brightest stars in the sky, some 60,000 times brighter than Sol. That far away, its distance is hard to measure, perhaps 1,400-1,600 light years. It is some 200 times the diameter of Sol, is near the end of its brief extravagant lifetime, and will become a red giant within the next few million years. Don't wake me.
Hazard, a retired BSU biology professor, also writes "Threescore and Ten" for The Pioneer's "Prime Time."