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Waning moon, Venus and Jupiter spectacular at dawn August 23

2014-aug-22-jupiter-venus-moon-night-sky-chart

Tonight is Aug 23, 2014

Moon Phase Courtesy U.S. Naval Observatory

Think photo opportunity at dawn on August 23, 2014 as the waning crescent moon swings close to the brilliant planets Venus and Jupiter. Darkness will be ebbing to morning twilight. You’ll need an unobstructed eastern horizon, and you’ll want to look low in the sky some 75 to 60 minutes before sunrise. This gorgeous celestial trio – the moon, Jupiter and Venus – is so very bright that some sharp-eyed people might even see the brilliant threesome after sunup. After all, the moon, Venus and Jupiter are the three brightest heavenly bodies to light up the sky, after the sun.

Wake up one and one-half hours or more before sunrise, and you might be able to spot the Beehive star cluster next to Jupiter through binoculars. Click here to find out when Jupiter climbs into your sky. Remember that the listed rising time of Jupiter (or any celestial body) presumes a level horizon.

Wake up before dawn's first light and you might catch the Beehive star cluster in the same binocular field with Jupiter. Good luck!

Wake up before dawn’s first light and you might catch the Beehive star cluster in the same binocular field with Jupiter. Good luck!

Jupiter, the largest planet of the solar system, rotates full circle upon its rotational axis in less than 10 Earth-hours. No other planet spins full circle upon its rotational axis in such a short period of time. Luckily, Jupiter’s speedy rotation often places the Great Red Spot on the Earth-side of Jupiter. You need a telescope to see the great Red Spot, a gigantic high-pressure hurricane that’s twice as large as our planet Earth. Click here to find out if the Great Red Spot is facing Earth right now – or at some given time.

In contrast to Jupiter, Venus is the solar planet that rotates most slowly. It takes Venus some 243 Earth-days to rotate full circle. The surface of Venus lies underneath perpetual cloud cover, so astronomers had to use radar to determine Venus’ rotation rate.

The Earth rotates 360o relative to the backdrop stars in about 23 hours and 56 minutes, and about 361o relative to the sun in about 24 hours. The Earth travels about one degree of its orbit in a day, so the Earth must rotate an extra degree (for a total of 361o) for the sun to return to its noontime position.

The Earth rotates 360o relative to the backdrop stars in about 23 hours and 56 minutes, and about 361o relative to the sun in about 24 hours. The Earth travels about one degree of its orbit in a day, so the Earth must rotate an extra degree (for a total of 361o) for the sun to return to its noontime position.

Rotation is based upon the planet spinning full circle relative to the backdrop stars – not the sun. This is known as the sidereal day. One rotation relative to the sun (noon to noon) is known as the solar day. Here, on Earth, the sun rotates full circle relative to the stars in about 23 hours and 56 minutes – and to the sun in about 24 hours. At Jupiter, the sidereal day is about 9 hours 55 minutes and 30 seconds – whereas the solar day is some three seconds longer. On Venus, where the planet rotates in retrograde (east-to-west), the sidereal day lasts for about 243 Earth-days – and the solar day for nearly 117 Earth-days.

What is sidereal time?

Jupiter, Venus and the moon on the morning of August 22, 2014, via Jeff Sullivan Photo.

Jupiter, Venus and the moon on the morning of August 22, 2014, via Jeff Sullivan Photo.

Bottom line: Be sure to see the waning crescent moon and the planets Jupiter and Venus adorning the morning dawn on August 23, 2014. This gorgeous celestial trio is so very bright that some sharp-eyed people might even see the brilliant threesome after sunup.