Astute skywatchers may have already seen the striking line of planets across the night sky in January. This week Mercury joins the queue. Now every other world in our solar system will be visible among the stars at the same time — if you know where to look.
According to Gerard van Belle, director of science at Lowell Observatory in Arizona, an alignment of seven planets is neither mystical nor particularly rare.
“On the scale of supermoon to death asteroid, this is more a supermoon sort of thing,” Dr. van Belle said. Still, the planetary parade, as the event is colloquially named, “makes for a very nice excuse to go outside at night, maybe with a glass of wine, and enjoy the night sky.”
Why are the planets aligned?
Whenever planets are visible in the night sky, they always appear roughly along the same line. This path, known as the ecliptic, is the same one that the sun travels along during the day.
This happens because the planets orbit around the sun in the same plane. Dr. van Belle likened the configuration to a vinyl record: The sun is in the center, and the grooves are the orbits of the planets around it.
Our point of view from Earth, then, is along one of those grooves, “looking out along the platter,” he said. This week, the planets are configured in such a way that all of them will be present in the sky at dusk from mostly anywhere on Earth.
Around the end of the month, Saturn will slip below the horizon and into daytime skies, ending the seven-planet parade. But stargazers will get another chance to see a planetary alignment in August, when several of our celestial neighbors will be visible in morning skies.
How can I see the parade?
Only a handful of the planets can be seen with the unaided eye, and the best evening to catch them all may vary by location. Astronomers recommend using a software program like Stellarium to figure out when and where to look.
To see the parade, find a dark place with a clear view of the western horizon at nightfall. Mercury and Saturn will be low in the sky, brushing past each other in the fading glow of the evening sun, which will make the pair difficult to spot.
Trace that line of sight higher to find Venus, the most brilliant planet in the sky.
“Venus, you cannot miss,” said Thomas Willmitch, director of the planetarium at Illinois State University. “You could be in a haze under streetlights, and there’s Venus, shining like a beacon to the west.”
Even higher up, almost directly overhead, will be Jupiter, sparkling at about one-tenth the brightness of Venus.
The string of planets ends in the eastern sky with Mars, easily discernible because of its pinkish tone. The planet is a few weeks past a close encounter with Earth, making it appear bigger than usual. According to Mr. Willmitch, this proximity has also cast the Red Planet in somewhat of a golden hue.
The other two planets are too far away to be seen without binoculars or a telescope. Uranus is about two fists west of Jupiter, Mr. Willmitch said, while Neptune is hiding between Venus and the western horizon.
But even if you can’t catch them all, Mr. Willmitch advised layering up and looking up anyway. “The sky is really beautiful in winter,” he said. “It’s a great time to go out and do some stargazing.”
