June nights are short! Fortunately, three bright planets emblazon the evening sky, competing for our cherished moments of observation.
Honour to whom honour is due: Jupiter continues to shine in the twilight and is first to capture our attention, as it should if we expect to see it while it’s still high enough in the sky. But time is of the essence! As the month begins, Jupiter appears 45 degrees up in the southwest at twilight; by the end of June, the giant planet is barely 30 degrees above the horizon as night falls, and the situation worsens in July. In telescopes of all sizes, Jupiter presents a host of interesting characteristics: From its Galilean moons to it atmospheric cloud-bands, it offers a veritable feast for the eyes!
Jupiter currently shines beneath the belly of Leo, to the left of a sickle-shaped group of stars that represents the head of the celestial lion. Observing the giant planet carefully with the naked eye for a few evenings, one will notice that it moves toward the left with respect to the background stars: Next year, Jupiter will be in Virgo, one constellation over from Leo. On the evening of June 11, the first quarter moon will sit 4 degrees to Jupiter’s left.
Mars blazes at the night
As the evening advances and Jupiter sinks toward the western horizon, Mars and Saturn rise steadily in the southeast, in the same part of the sky. Mars was at opposition during the latter half of May and is currently closer to Earth than it will be for the next two years. Right now, it’s practically as bright as Jupiter and shines with a distinctive orange colour, hence the name “Red Planet”. On June 30, Mars reaches the western end of its retrograde loop in Libra: the next day it begins moving eastward, and over the coming months you can track its dizzying dash among the constellations. The gibbous moon will form a flattened triangle with Mars and Saturn on the evening of June 17.
The Red Planet is twenty times smaller than Jupiter, but it’s much closer to Earth. Seen through a telescope, the apparent diameter of the Martian globe is currently half that of Jupiter. At moderate magnification, subtle surface details are difficult to observe and require some effort to discern. Though Mars demands patience, the rewards are great for those willing to devote the time and energy needed.
Saturn at opposition
Saturn, the other “star of the evening”, arrives at opposition on June 3 in Ophiuchus. This gas giant is somewhat smaller than Jupiter, and twice as far from Earth. Through a telescope, though Saturn appears half Jupiter’s size, the planet’s magnificent rings more than compensate. Saturn is currently situated several degrees to the left of Mars and culminates in the south, slightly more than an hour after the Red Planet. During the night of June 18 to 19, a gibbous moon will sit just 3 degrees below Saturn.
Short solstice nights
This year the summer solstice occurs on June 20 at 6:34 p.m. EDT. We know that in the Northern Hemisphere this marks the longest day, but it’s also the shortest night. For the past several weeks, we’ve seen that the Sun not only sets late (and rises early), but that twilight also seems to take forever: Along the horizon, colours can still be seen late into the evening, and they reappear several hours before sunrise. Astronomers consider that nightfall is complete when the Sun is 18 degrees below the horizon: This marks the end of astronomical twilight, which can be calculated in the same way as sunrise or sunset.
As such, at the latitude of Montreal (45.5° N), true darkness only lasts three hours on the day of the solstice. At the latitude of Québec City (46.8° N), it’s reduced to 2 hours 20 minutes; and in Saguenay (48.4° N), it lasts barely 40 minutes! In Sept-Îles (50.2° N), astronomical twilight never fully ends during this period. More northerly regions, near the Arctic Circle (66.5° N), find themselves under the influence of the famous midnight sun, with varying amounts of daylight illuminating the nighttime hours.