It’s Not Over Till The Fast Planet Sinks

This week and early next will be your last chance to see five planets — six if you count Earth — at dawn. Nature's even throwing in a bonus Mercury–Moon conjunction.

The author demonstrates the wide span — 115° this week — between the five morning sky planets at dawn on Sunday, January 31st, when a bright last-quarter Moon dominated the sky.
Bob King

People ask me whether they might still see "five planets in a row," and my answer remains an emphatic "yes!". But there's a deadline coming, so I encourage you to have a look at dawn either this week or early next. By Valentine's Day, the show's pretty much over. Five will drop to four.

Five planets and a bright Moon at dawn photographed over Rome on February 1, 2016.
Gianluca Masi

Although the Moon shined over-bright during my morning foray on Sunday, it thins this week to a crescent and meets Mercury in a striking conjunction two days before new Moon. Right now is also the best time to catch Mercury, which crests around 7° altitude (from 40° N)  before it's lost in bright twilight. The planet has been pushing west into the morning sky since late January, rising a little higher each morning. Come February 7th, it reverses direction and traipses back toward the Sun.

Here's the view on Thursday morning, February 4th, about 45 minutes before sunrise from the central U.S. at 40° north latitude. Moon positions are shown through Saturday, February 6th
Stellarium

As pointed out in an earlier story by Sky & Telescope's Kelly Beatty, the planets neatly follow the arc of the ecliptic, the plane of Earth's orbit projected as a line into space and traced out by the Sun once a year. Rarely has the essential flatness of the solar system been rendered so obvious to the naked eye. For the new student of astronomy trying to make sense of where the planets travel, there's no more instructive time than now to see the concept in the flesh.

The last time the planets lined up like this occurred 11 years ago in late December 2004 to early January 2005. It next occurs in August, making 2016 rich in multiple-planets-at-a-glance sightings.

A closer look at the conjunction of the thin Moon and Mercury, with Venus nearby, before sunrise on Saturday morning, February 6th.
Stellarium

To plan your outing, find a suitable location with a wide open view to the south and particularly to the southeast, where the low-lying planets Venus and Mercury will be hiding out. Arise about 1½ hours before sunrise when the first hint of dawn brightens the eastern sky and get set up for viewing.

Jupiter stands relatively high in the southwestern sky at this time; its brilliance makes it easy to identify. To find the other four, reach your balled fist to the sky and count off three fists to the left of Jupiter to arrive at Spica, Virgo's brightest star. Two fists farther left (east), you'll bump into fire-colored Mars. A fainter star teases your eye a little more than 1° to the lower right of the planet. That's the tongue-teaser Zubenelgenubi, Libra's second brightest star, which sits almost directly on the ecliptic.

After a reshuffle, five planets will again be visible at dusk in August this year.
Stellarium

Slide nearly three more fists to the east while dropping southward, and say hello to Saturn and Antares. Saturn's the brighter and higher "star." Three more fists east and south will bring you to Venus, shining brilliantly despite its low altitude. Mercury glows just 5° — or three fingers — farther east and south.

Mercury was even lower in the sky on January 31st when this photo was taken but still very easy to see. This week it's higher yet. Click photo to see a live orrery showing the layout of the planets in the solar system.
Bob King

Take in the sight, the swelling light, and you'll be in orbit the rest of the day.