- June 17, 2015 - Planétarium : Astronomical News
Conjunctions between Venus and Jupiter aren’t all that rare; for example, these two planets, the brightest in the sky, come together every 13 months on average. But no matter the frequency, planetary conjunctions are always impressive to see, especially when the Moon enters the scene… and this month, the sky offers the best conjunction of the year!
Two “stars” in the twilight
By mid-June, Venus and Jupiter illuminate the western sky at twilight, 30 minutes after sunset; and since they are the two brightest planets they are impossible to miss. Venus, “the Evening Star”, is the brighter of the two and is located about ten degrees to the lower right of Jupiter... But the situation changes rapidly. The two planets are heading toward each other, and with each passing evening the gap between them diminishes by roughly half-a-degree, which is equivalent to the apparent diameter of the full moon.
The Moon enters the scene
This planetary convergence continues; but in the meantime, a thin lunar crescent enters the scene and rapidly rises above the western horizon. On June 19, the Moon lies directly below Venus; and the following evening, it rests to the lower left of Jupiter. That evening, the trio will form a perfect isosceles triangle. But after June 20, the Moon moves away from the two planets and the triangle breaks up.
Binoculars will enhance your view of the thin lunar crescent, and will also help you observe the soft glow of earthshine — sunlight reflected by our planet onto the dark part of the lunar face. This combination of the crescent Moon and planets, suspended in the twilight, is one of the most beautiful celestial sights there is!
The conjunction reaches its apex
The two planets continue along their path, and the result is predictable: On the evening of June 30, at twilight, Venus comes to rest just one third-of-a-degree below Jupiter! This is the closest conjunction of the year, and an ideal occasion for telescopic observation!
An hour after sunset, the giant planet’s atmospheric cloud bands, and its four Galilean moons, will be visible just above a crescent planet Venus… all in the same eyepiece field of view! An exceptional sight not to be missed!
