ON any night in June, 2015, look for the queen and king of planets – dazzling Venus and bold Jupiter – as these two worlds appear in your western sky first thing every nightfall. They’ll appear in your evening sky throughout June 2015, and they’ll be drawing closer together each evening!
Venus will pass Jupiter in late June/early July, 2015. At that time – especially on the nights of June 30 and July 1 – you can witness the closest Venus-Jupiter conjunction until August 27, 2016.
These very bright worlds will be hard to miss (unless it’s cloudy!) because Venus and Jupiter rank as the third-brightest and fourth-brightest celestial bodies, respectively, after the sun and moon.
As dusk turns into darkness, note the star Regulus above Jupiter, on line with Venus and Jupiter. Day by day, watch as Venus and Jupiter race toward Regulus, the brightest star in the constellation Leo the Lion. In fact, you can use these three luminaries – Regulus, Jupiter and Venus – to imagine the ecliptic crossing the sky with your mind’s-eye. The ecliptic is the Earth’s orbital plane projected onto the sky’s dome. Because the planets orbit the sun on nearly the same plane that Earth does, the solar system planets are always found on or near the ecliptic.
At present, the planets Venus and Jupiter are both heading eastward (upward) along the ecliptic, toward the star Regulus. You might think Jupiter should get to Regulus first, since the king planet lodges so much closer to Regulus, the only 1st-magnitude star to sit almost squarely on the ecliptic. However, the closer that a planet resides to the sun, the faster that the planet travels in its smaller orbit. Venus, the second planet outward from the sun, races along at 35 kilometers per second whereas Jupiter, the fifth planet outward, plods along at 13 kilometers per second.
But that’s not all. Jupiter’s orbital path is a solid seven times longer than that traveled by Venus. For that reason, Venus will zoom toward Regulus day by day, whereas Jupiter will travel at a snail’s pace.
Be sure to circle July 18, 2015 on your calendar as well. Venus will be almost in conjunction with Regulus, a slight bit ahead of Jupiter in the great race to the constellation Leo’s brightest star. On July 18, the crescent moon, Venus and Jupiter will all fit within a circle sporting a diameter of less than four degrees. (Four degrees of sky approximates two finger-widths at an arms length.) Don’t miss out on this close-knit celestial grouping on June 18, featuring the moon, Venus and Jupiter – the brightest, second-brightest and third-brightest orbs of nighttime, respectively.