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Moon and Jupiter in Leo on June 10

Tonight – June 10, 2016 – as soon as darkness falls, look for the waxing crescent moon in the western sky. That nearby bright “star” is actually the king planet Jupiter, the brightest starlike object in the evening sky. The fainter light on the other side of the moon on June 10 is Regulus, the brightest star in the constellation Leo the Lion.

There’s no way to mistake Regulus for Jupiter – or vice versa. Jupiter is by far the brighter object, outshining Regulus by some 20 times. That’s not to say that Jupiter is the more luminous of these two celestial lights. It’s not.

Jupiter, being a planet, shines because it reflects the light of the sun.

Regulus is a star, so it shines by its own light.

If Regulus were at the sun’s distance from Earth, it’d visually be 150 times brighter than our sun. Or, another way of putting it, the sun at Regulus’ distance of 79 light-years would appear 1/150th as bright as Regulus. You’d need an optical aid to see the sun at this far away.

Three planets - Jupiter, Mars and Saturn - plus two bright stars - Regulus and Antares - light up the June 2016 evening sky all month long. The green line depicts the ecliptic - the sun's yearly path in front of the constellations of the Zodiac.

Three planets – Jupiter, Mars and Saturn – plus two bright stars – Regulus and Antares – light up the June 2016 evening sky all month long. The green line depicts the ecliptic – the sun’s yearly path in front of the constellations of the Zodiac.

The moon travels in front of all the constellations of the zodiac in about four weeks. As seen from Earth, the moon moves much more quickly relative to the backdrop stars of the zodiac than does any other celestial object.

For instance, the moon will move past Jupiter on June 11, and then will leave the constellation Leo to enter the constellation Virgo after a few more days.

Jupiter won’t enter Virgo until August 8, 2016.

Bottom line: Watch for the moon and the planet Jupiter to light up the constellation Leo the Lion as soon as darkness falls on June 10, 2016.

Bruce McClure

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