Enjoying EarthSky? Subscribe.

268,131 subscribers and counting ...

See moon and Jupiter before sunup

Get up before sunrise on November 25, 2016 – or any of the mornings around this date – to view the waning crescent moon pairing with the king planet Jupiter in the predawn sky. Also look for the star Spica on these November mornings. Afterwards, you can use this key star of the zodiac to observe the four-month retrograde of Jupiter in 2017.

Let’s back up. You simply can’t miss the moon and Jupiter before dawn now. The moon has been taking aim on Jupiter for several mornings. On November 25, they’re closest for the Americas … beautiful as seen from around the world.

The moon ranks as the second-brightest celestial object in all the heavens, after the sun; Jupiter ranks as the fourth-brightest, after the sun, moon and planet Venus. You’ll find Venus in the evening sky now, so there’s no way mistake Jupiter anything else up before dawn.

If you’re up and about before dawn’s first light, also try to catch Spica, the brightest star the constellation Virgo the Maiden, near the moon and Jupiter. Although Spica pales next to Jupiter, it’s a celebrated 1st-magnitude star, ranking as the 16th brightest star in all the heavens.

Follow the arc to Arcturus, and speed on to Spica.

You can be sure you’ve located Spica by using the Big Dipper as a reference point. As the saying goes: “follow the arc to Arcturus, and speed on to Spica.”

Because Spica is a star of the zodiac, the sun, moon and planets sweep by Spica in predictable cycles. Note Jupiter’s position relative to Spica on the morning of November 25, or any of the mornings around now. Then watch for Jupiter to edge eastward, toward the star Spica, over the next two months. By January 20, 2017, Jupiter will have a conjunction with Spica, passing 4o north of this star on our sky’s dome. Shortly after that, on February 6, 2017, Jupiter will reach its stationary point in front of the stars, as the king planet starts its retrograde (westward motion) in front of the constellation Virgo.

As good luck would have it, Spica serves as a brilliant reference point for watching upcoming retrograde of Jupiter from February 6 to June 10, 2017. In other words, you’ll be able to see Jupiter moving westward with respect to this point throughout this period. Then, after June 10, you can see Jupiter appear to change direction and begin moving eastward on our sky’s dome again.

Midway through this retrograde – on April 7, 2017 – Jupiter will be at opposition. At this time, Earth will pass more or less between the sun and Jupiter for this yearly orbit. Thus in April, Earth will swing closest to Jupiter for the year, and Jupiter, in turn, will shine at its brightest best in Earth’s sky. Moreover, at opposition, Jupiter will shine all night long, from dusk until dawn.

So Spica is really a very useful star to know in 2017. It can help you enjoy and appreciate mighty Jupiter.

And, by the way, only four 1st-magnitude stars lie close enough to the moon’s orbital path to be occulted (covered over) by the moon as it makes its monthly journey across our sky. Spica is one of these. Regulus, Antares and Aldebaran are the other three.

The moon passes fairly close to Spica each month, but hasn’t actually occulted – passed directly in front of – Virgo’s brightest star for quite a few years. The moon’s last occultation series with Spica happened on a monthly basis from July 25, 2012, to December 27, 2013. The next occultation series will occur from June 16, 2024, to November 17, 2025.

In this July 1997 still frame captured from video, the bright star Aldebaran has just reappeared on the dark limb of the waning crescent moon in this predawn occultation.  Image via Wikipedia

Lunar occultation of bright star Aldebaran in 1997. The star has just reappeared on the dark limb of the waning crescent moon. So, you see, occultations are very beautiful! Image via Bart Benjamin, via Wikipedia

Bottom line: The moon sweeps close to Jupiter on the morning of November 25, 2016 and appears near the planet for several mornings around then. Look for the star Spica near the moon and Jupiter, and then use this key star of the zodiac to observe the upcoming 4-month retrograde of Jupiter from February 6 to June 10, 2017.

Bruce McClure