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Moon approaching Jupiter on June 29

Tonight – June 29, 2017 – you can’t miss the king planet Jupiter, given a clear sky! As soon as dusk or darkness falls, look first for the rather wide waxing crescent moon. That “star” in the moon’s vicinity tonight is actually Jupiter, the brightest starlike object to adorn the evening sky. The moon is approaching Jupiter as we speak, and will be noticeably closer to Jupiter as darkness falls tomorrow, on June 30.

Do you have binoculars? You can search for the Virgo star Zavijava (Beta Virginis) in the same binocular field with the moon. Although this faint star is easily visible to the unaided eye on a clear, dark night, it might be hard to see in the glare of the June 29 moon. The sky chart below is for mid-northern North American latitudes. On this same date at mid-northern latitudes in Europe and Asia, tonight’s moon will appear farther west (right) of Jupiter and Zavijava than it does in North America.

This chart of the moon and the Virgo star Zavijava (Beta Virginis) is for North America. On this same date in Europe, the moon will be approximately 3o (6 moon-diameters ) west or right of Zavijava. In Asia, the moon will be about 6o (12 moon-diameters) farther west than it is in North America.

As evening deepens, watch for the moon, Jupiter and Zavijava to move westward across the sky. At mid-northern latitudes, all three will set by around local midnight (1 a.m. Daylight Saving Time) tonight. Click here for an almanac telling you when the moon and Jupiter set in your sky.

The star Zavijava (Beta Virginis) almost aligns with the September equinox point. Sky chart via the International Astronomical Union (IAU) and Sky & Telescope.

The star Zavijava sits almost squarely on the ecliptic – the sun’s annual pathway in front of the constellations of the zodiac. But that’s not all. This star nearly marks the September equinox point, or where the sun lodges in the constellation Virgo on the day of the September equinox, which comes this year on September 22, 2017.

Purportedly, this star also played a pivotal role in helping to confirm Einstein’s general relativity theory during the total solar eclipse of September 21, 1922.

Earth’s spin causes the moon and Jupiter to go westward throughout the night. Meanwhile, due to its own motion in orbit, the moon travels eastward relative to the backdrop stars and planets of the zodiac. Tonight – June 29, 2017 – the moon will move eastward, toward Jupiter, at the rate of about ½ degree (the moon’s own angular diameter) per hour. That’s why everyone around the world will see the moon closer to Jupiter on the sky’s dome tomorrow, as darkness falls on June 30.

Bottom line: Tonight – June 29, 2017 – you can’t miss the moon and king planet Jupiter, given a clear sky!

Bruce McClure

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