The coming month brings shooting stars, pretty planets, and plenty more reasons to look up at the night sky. You’ll even have the chance to catch the eerie pyramid-shaped zodiacal light.
So dust off those binoculars and mark your October calendar!
Mercury at it Best—Week of October 1
Skywatchers this week get a chance to get their best view of the year of Mercury, the trickiest planet to spot with just your unaided eyes.
Check out the innermost planet in the solar system just after it passes its greatest elongation September 28, which is the farthest the planet can get from the sun from our vantage point on Earth. About 45 minutes before sunrise, hunt down the most challenging planet to see with the naked eye.
Mercury is the smallest major planet in the solar system, only slightly larger than Earth’s moon. And it lies so close to the sun that it takes only 88 days to complete one orbit around the star. To spot Mercury, look for a faint star-like object eight degrees above the horizon—equal to the the width of your clenched fist held at arm's length.
The planet will be at its most visible because it will be higher in the eastern sky, away from the glare of the rising sun, than on any other morning in 2016.
And here’s a viewing tip: Binoculars will help you initially track down the faint planet and crescent moon in the glare of the morning twilight. Also even a small telescope can also reveal Mercury as a disk that appears half lit, like a tiny version of the quarter moon.
Here are some of the other exciting astronomical wonders in store for sky-watchers this week.
Zodiacal Lights—October 1-15
Starting about an hour before sunrise on Saturday, October 1, and lasting the next two weeks, keen skywatchers in the Northern Hemisphere can hunt down one of the most elusive astronomical phenomena visible in the sky: the zodiacal light.
This pyramid-shaped beam of light is easily mistaken for the lights of a far-off city just over the dark horizon in the countryside, and has also been called “false dawn.” But this light is more ethereal; it is caused by sunlight reflecting off cosmic dust between the planets.
Amazing to think that today we’re peering at billions of dust-sized particles that were left behind after the planets formed about five billion years ago.
Orionids Ramp Up—October 2
In the pre-dawn hours, the Orionid meteor shower kicks off with a sprinkle of shooting stars. But the best of this sky show will peak on the 21st with as many as 20 shooting stars per hour.
Even if you’ve never heard of the Orionid meteor shower, you’ve probably heard of its source. The shooting stars you’re seeing now are part of the debris shed from the most famous of all Earth's icy visitors, Halley’s Comet. (Learn more about the Orionids.)
Moon and Venus—October 3
A half-hour after your local sunset, look toward the very low southwestern sky for a razor-thin crescent moon pairing up with bright star-like Venus. The two objects will only be five degrees apart—equal to the width of your three middle fingers held together.
Uranus Primetime—October 15
The green ice giant Uranus officially reaches opposition, which means the outer planet will be at its biggest and brightest in our skies for the entirety of 2016.
Uranus will appear opposite the sun in the sky and rises in the east after sunset in the constellation Pisces. Nearby, the full moon will make it easier to find the tiny disk: look for the planet less than four degrees underneath the moon. Both objects should fit easily into the field of view of a standard pair of binoculars.
You can try spying Uranus, which is at magnitude 5.7, with the naked eye if you’re in dark countryside. You may, however, find it easier to pick out its tiny green-blue colored disk with binoculars or a small telescope. Its distinctive hue is caused by absorption of the red portion of the spectrum of sunlight by molecules of methane in its atmosphere; blue and green are reflected back to our eyes.
Bull’s-Eye Winks—October 18
After darkness falls, look toward the eastern sky for a gibbous moon positioned close to the orange star Aldebaran, which is the red eye of the constellation Taurus, the bull.
Lucky skywatchers across Mexico, Central America, southeastern Canada, the eastern United States, southern Europe, and Northwestern Africa should actually see the moon cover, or occult, Aldebaran.
Orionids Peak—October 21
Look for the Orionids to reach their most prolific, with numbers reaching upwards of 20 shooting stars per hour visible from dark locations.
The meteors appear to radiate from the northern part of the shower’s namesake constellation Orion the Hunter, which rises in the northeast just before local midnight for mid-northern latitudes at this time of year.
Orion is one of the easiest star patterns to recognize thanks to its three bright stars that line up in a perfect row, marking the mythical figure's belt.
Moon and Lion’s Heart—October 25
In the pre-dawn hours, face due east and watch the thin crescent moon hanging underneath the bright star Regulus, which marks the heart of the constellation Leo, the lion. The two bright objects will be less than two degrees apart—a bit wider than your thumb held at arm’s length.
Jupiter and Moon—October 28
Once again the moon catches up with a planet, but this time it's the largest planet in the entire solar system and one of the brightest in the night sky.
Jupiter and the moon will make for a stunning sight with just the naked eye—and this is a great photo opportunity against the brightening dawn skies due east.
Saturn and Venus—October 30
Just as the evening twilight sets in, look for Venus and the much fainter Saturn to make a pretty pairing in the low southwest skies.
Joining them is an orange star named Antares, the eye of the constellation Scorpius. Binoculars will help show the planetary pair in all their glory, while a small telescope will reveal Saturn’s rings and the tiny disk of Venus too.