To listen to the TV news you’d think the well-publicized planetary lineup is pretty much over. The good news is that this visual treat has just begun. Jupiter, Venus and Mars have been trolling the morning sky for months. A few weeks ago, they were joined by Saturn, emerging low in the southeastern sky at dawn. That made four planets. When Mercury appeared on the scene this week, swinging from the evening sky around the other side of the sun into the morning, the final piece of the puzzle fell into place. Five naked-eye planets! Six if you count Earth.
Right away, when we hear “planetary alignment” you might picture a tight grouping of the planets, but more often the planets are strung out across a broad swath of the sky, necessitating a map to tell them apart from any bright stars that might be nearby. And so it is with this late-January-through-mid-February gathering which spans an arc not one, not two but 11 fists (110°) across the southern sky.
We’ll start on the “easy end” at Jupiter and work our way eastward (to the left as you face south) to Mercury, the lowest and most difficult of the five to see. You’ll need a viewing spot with a great view to the south and especially to the southeast where the innermost planet lurks. You’ll also need to know the time of sunrise, so you can start your planet watch about an hour beforehand.
Face the south direction around 45 minutes to an hour before sunrise and look off to your right to spot a brilliant “star” three fists above the southwestern horizon. That’s Jupiter. Now work your way about three fist to the east (left) and you’ll arrive at Spica, Virgo’s brightest star. Mars is nearly identical in brightness to Spica and gleams a little more than one fist to its left. The two make a pair of level “eyes” in the southern sky.
From Mars, slide left and down about three fists to another pair of bright points in a vertical line almost exactly perpendicular to Spica and Mars. The top one is Saturn and the bottom is Antares, the brightest star in Scorpius. Keep going down and eastward to the brightest of all the planets, Venus. Unmistakable!
Now that you’ve cut your teeth on these, you’re ready for the most challenging object — Mercury. For northern U.S. and southern Canadian skywatchers, it’s only three fingers above the horizon and the faintest of the five. Currently at 2nd magnitude, you’ll almost certainly need binoculars to spot it hiding in the yellow glow of dawn. If you live in the southern U.S., the planet is higher up in a darker sky and a little easier to see.
As we move into the final week of this month and the first week of February, Mercury rises higher in the southeast and brightens. On February 6th, it will join Venus and the waning crescent moon in a very pretty grouping at dawn. All the other planets will still be around, too. As you can tell, there are lots of opportunities in the nights ahead to view all five naked-eye planets.
The last time the planets lined up like this occurred 11 years ago in late December 2004-early January 2005. More often, a couple planets are visible at night and a couple in the morning sky with Venus or Mercury sometimes lost in the solar glare. Seeing all five all at once happens infrequently.
On the maps, you’ll notice that the planets lie along an imaginary line in the sky called the ecliptic. The ecliptic is a projection of Earth’s orbit into space; since all the planets orbit the sun in about the same plane as Earth, they all appear to travel along the same “highway in the sky” along with the moon and sun. Earth’s brothers and sisters always hang out along the ecliptic which runs through the 12 constellations of the zodiac.
If you get totally burned on this event, you won’t have to wait long for the next which occurs in mid to late August, when all five will be bunched up in the western sky at dusk.
Before signing off, while we’re talking about the planets, you MUST see today’s Astronomy Picture of the Day (APOD) which features a spectacular, one-of-a-kind image of the space station passing directly in front of the planet Saturn.
UPDATE: I learned today (Jan. 23) that this image has been misrepresented. It’s a composite of several videos/images taken at different times, so what you see isn’t what actually happened. Sorry.