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1st quarter moon with Jupiter June 30

Tonight – June 30, 2017 – be sure to watch the magnificent pairing of the moon and Jupiter as darkness falls. The moon and Jupiter rank as the brightest and third-brightest heavenly bodies of nighttime. What’s the second-brightest? It’s the blazing planet Venus, which resides exclusively in the morning sky for the rest of 2017.

Also, look for a bright star near Jupiter and the moon. This star is Spica – near Jupiter throughout 2017 – brightest light in the constellation Virgo.

The moon reaches its first quarter phase on July 1, 2017 at 0:51 UTC. Converting Universal Time to the clock time at North American time zones, the moon’s first quarter phase happens on June 30, at 9:51 p.m ADT, 8:51 p.m. EDT, 7:51 p.m. CDT, 6:51 p.m. MDT 5:51 p.m. PDT and 4:51 p.m. AKDT.

The Earth and moon are like mirrors to each other. If you were on the moon tonight, you’d see a last quarter Earth. Simulation of last quarter Earth as viewed from 1st quarter moon (2017 July 1 at 0:51 UTC). The terminator or shadow line represents Earth’s line of sunsets. Image via Fourmilab.

At quarter moon, the moon’s disk is half-illuminated by sunlight and half-immersed in the moon’s own shadow. The lunar terminator – the shadow line crossing between the moon’s day and night sides – shows you where it’s sunrise on the waxing first quarter moon. The moon is said to be at first quarter because, in its cycle of phases, the moon is one quarter the way from one new moon to the next.

Read more: Understanding moon phases

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As always, the moon moves eastward in front of the constellations of the zodiac. Watch for the moon over the next several nights, as its distance from Jupiter on our sky’s dome increases. You’ll really be watching the moon’s own motion in orbit around Earth.

Jupiter ended its retrograde motion earlier this month (June 10), which means the best time of 2017 for viewing this dazzling planet has ended.

Thus Jupiter is now moving eastward along the ecliptic again – going toward Spica, Virgo’s brightest star. Keep watching as Jupiter moves toward Spica, to pass 3o north of this star on September 5, 2017.

Because Jupiter is roughly in the same area of sky as the moon this evening, you might expect this world to exhibit a similar phase to tonight’s moon. Not so. Jupiter is so far distant from Earth that it always appears nearly 100% illuminated from our earthly perspective.

Bottom line: The dazzling planet Jupiter is near the first quarter moon on June 30. Enjoy the waxing moon and Jupiter on July 1, too!

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Bruce McClure

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