At a time of year when the nights are shortest, two bright planets will attract our attention at nightfall.
On June 21 at 12:24 a.m., the solstice arrives and astronomical summer begins in the northern hemisphere. After the dark, cold winter months, we can finally bask in the long hours of sunlight that the solstice brings. Yet for lovers of the starry sky, this means that darkness occurs later and that the pitch-black night lasts only a few hours.
Nevertheless, in the minutes after sunset, when the sky begins to darken, a bright object appears above the south-southwest horizon. Though it may look like a star, it’s in fact a planet. Two months after its opposition, the gas giant Jupiter catches our eye and rules the sky on June nights.
Through a telescope, Jupiter reveals turbulent and colourful cloud bands, cyclones, festoons, and shadow transits of four Jovian moons. Whatever your observation equipment or level of experience, the spectacle is dazzling. Observe Jupiter whenever you can while the planet is still high enough in the sky. Try to make out the subtle differences in the light and dark bands. You’ll eventually have a rare evening when our own atmosphere is extremely stable, and as though you’re removing a distorting lens, the details visible in Jupiter’s atmosphere, 750 million kilometres away, will appear much sharper and clearer. An observation like this is an unforgettable experience.
On the evening of June 3, the gibbous Moon lies at less than 1.5 degrees above Jupiter. The first quarter Moon is also close to the planet on the night between June 30 and July 1.
Jupiter is now shining in Virgo. Note the presence of Spica, the Alpha star in this large constellation, a few degrees to the lower left of the planet. Its Latin name refers to the spike (or ear of wheat) that the Virgin holds in her hand. Spica’s blue-white glow contrasts with the creamy white of Jupiter. Spica also serves as a reference point for following Jupiter’s movement over the celestial sphere. In the coming weeks, the gas giant will gradually approach the star.
Located 250 light-years from Earth, Spica is in fact a binary system, two stars that orbit each other in just over four days. Its bluish colour is evidence of the high temperature of its two components. One star is 10 times more massive than the Sun and has a surface temperature of 22,000 degrees (the Sun’s temperature is “only” 5,700 degrees). Its companion is almost seven times more massive than the Sun and has a temperature of over 18,000 degrees. Together, the two stars emit more than 13,000 times the Sun’s energy, but mostly as ultraviolet rays.
Saturn and the Milky Way
Just as Jupiter is attracting our attention, another bright body, Saturn, makes an appearance in the southeast at twilight. The ringed planet is in opposition on June 15. During this period, it’s visible all night, culminating in the south in the middle of the night and disappearing below the southwest horizon at dawn. This year, the gas giant lies again in Ophiuchus, just above Scorpius and Sagittarius. This is unfortunately the southernmost part of the ecliptic (the apparent path of the Sun, Moon and planets across the sky). Consequently, in our latitudes, Saturn rises just about 20 degrees above the horizon. The view of its famous rings is therefore not ideal even though they’re at their maximum tilt in 2017. Still, it’s worth observing the planet through a telescope. On the evening of June 9, barely 2.5 degrees separate the full Moon and Saturn as the two bodies rise together. They remain neighbours throughout the night.
Saturn lies in a field of stars. Indeed, the region of Sagittarius and Scorpius coincides with the centre of the Milky Way, which is found on the southern horizon in the middle of the night in June. Far from cities and light pollution, you can make out this diffuse arc, which rises toward the northeast and crosses the Summer Triangle. The triangle, which includes the stars Vega, Altair and Deneb, forms a big “V” for “vacation” and arrives in time to mark the end of the school year.
Venus at the break of dawn
As mentioned earlier, the nights around the solstice are short. Just over four hours after twilight ends, the first light of dawn can be seen even though it’s is only 3 a.m. Thirty minutes later, as the stars begin to fade into the blue of the sky, brilliant Venus emerges above the east-northeast horizon. The bright planet is at its greatest elongation on June 3, 46 degrees to the west (right) of the Sun. Through a small telescope, its disc appears as a half Venus early in the month and gradually changes into a gibbous Venus later in June. The crescent Moon lies near the Morning Star on June 20 and 21.