Don’t Miss: Moon and Jupiter Pair Up Low in the East
When: Around 10:00 p.m. local time on Sunday, Nov. 9 (look low toward the east-northeast).
Look for a waning gibbous Moon about 72% illuminated with a brilliant, steady “star” just beneath it — in fact, that “star” is the planet Jupiter. The apparent separation between the Moon and Jupiter will be roughly 4.5° (about half a clenched fist held at arm’s length).
Jupiter currently lies among the stars of Gemini, near the point where the ecliptic reaches its most northerly declination (~+23°). That northern position favors observers in the Northern Hemisphere because the planet spends more time above the horizon and climbs higher in the sky at mid-transit. Observers in the southern U.S. may find Jupiter very near the zenith when it crosses the meridian in the early morning.
If you look roughly 3.5° to the upper-left of the Moon you’ll spot the bright star Pollux. Pollux is a first-magnitude star (one of the ~21 brightest in the sky) but shines at only about 1/28 the brightness of Jupiter, so Jupiter will dominate the scene.
The Moon moves eastward relative to the background stars at about its own apparent diameter each hour, so its position relative to Jupiter and Pollux will shift noticeably during the night.
Local alignment times (approximate)
The exact moment when the Moon appears nearly collinear with Pollux and Jupiter — seeming to sit between the star and the planet — depends on your longitude. In the continental U.S. the approximate times are:
- Eastern: ~1:45 a.m.
- Central: ~12:25 a.m.
- Mountain: ~11:20 p.m.
- Pacific: ~10:00 p.m. (very low above the east-northeast horizon)
By dawn Monday the Moon will have moved well to the east, and the configuration will look different.
Viewing tips
Jupiter is currently one of the best planets for observation and will remain so through the winter and into spring. However, atmospheric turbulence (seeing) often limits sharp telescopic detail until a planet climbs to about 30° altitude. That altitude (roughly three fists at arm’s length) is commonly considered the dividing line between objects that appear “low” and those that are “well placed.”
If you use a small telescope this weekend you should be able to see the four Galilean moons: Io and Ganymede on one side and Europa and Callisto on the other. Their changing positions are fun to watch across hours or nights.
Article by Joe Rao, instructor and guest lecturer at New York’s Hayden Planetarium. He writes about astronomy for Natural History, Sky & Telescope and other publications.
