October guide to the Planets

The Greater Hazleton Area Astronomical Society

Chart: Mars next to horizon at nightfall close to line of ecliptic and 3 positions of Harvest Moon.

In late September and early October 2020, the Northern Hemisphere’s Harvest Moon shines in the vicinity of the brilliant red planet Mars. Mars is super bright now! Read more.Mars, 4 positions of moon along ecliptic, with Pleiades and position of Uranus marked with an arrow.

No, Mars won’t be in front of the moon on October 1, 2020. The moon looks larger on the chart than in the real sky. On October 1 and 2, the Harvest Moon and Mars will be close! From most places worldwide, the moon will swing a touch south of Mars on October 2. For the fun of it, we also show the planet Uranus, but it won’t be visible to the unaided eye on these moonlit nights. Read more.Chart: Nearly vertical ecliptic line with three dots close together on it.

On the mornings of October 2 and 3, 2020, Venus (brighter) and the bright star Regulus will appear near one another in the east before sunup. Here’s the view from North America, where Venus will appear about half a degree above Regulus on October 2, and about half a degree below Regulus on October 3. A degree is about the width of your little finger held at arm’s length. Their conjunction will come on October 3, at 00:00 UTC, at which time Venus will pass a scant 0.1 degree south of Regulus. That’s very close! As seen from western Asia, Venus will come achingly close to brushing against Regulus. Read more.Venus and Regulus close to ecliptic with 4 positions of crescent moon.

Watch for the waning crescent moon near the dazzling planet Venus for several mornings, centered on October 13 or 14, 2020. Read more.Saturn and Jupiter along ecliptic with 3 positions of waxing moon.

The moon goes by the two close-knit evening planets Jupiter and Saturn from October 21 to 23, 2020. Read more.Steep line of ecliptic with Mercury and Spica near horizon.

This chart is for the Southern Hemisphere, where people will enjoy the best evening apparition of Mercury for the year in September-October 2020. As seen from the Northern Hemisphere, Mercury will be deeply submerged in evening twilight and hard to see. Read more.Mars with 3 positions of moon and arrow marking position of Uranus.

This month, the moon swings by Mars for a second time in late October 2020. Read more.https://ca59a626045fa6161e33b49747f62304.safeframe.googlesyndication.com/safeframe/1-0-37/html/container.html

Jupiter and Saturn come out first thing at nightfall in October 2020, and will continue to do so until the year’s end. They are near one another on the sky’s dome, with Saturn following Jupiter westward across the sky from dusk/nightfall until late night.

At mid-northern latitudes, Jupiter and Saturn set at late evening; and from the Southern Hemisphere, they stay out till midnight or later.

Several months ago, in July 2020, these gas giant worlds, Jupiter and Saturn, reached their yearly opposition.

Earth – in its yearly orbit – swung between these outer worlds and the sun in July 2020. Thus we were closest to Jupiter and Saturn for the year in July. Jupiter and Saturn, in turn, shone at their brightest best and were out all night long.

Sky chart: Jupiter and Saturn on line of ecliptic, and the Teapot asterism.

If you notice just one object in the sky after sunset, it might be very bright Jupiter. This planet outshines all the stars, plus it’s near another bright planet, Saturn. You can’t miss these two. Jupiter and Saturn are highest up for the night at nightfall in October. Before 2020 ends, Jupiter and Saturn will undergo a great conjunction.https://ca59a626045fa6161e33b49747f62304.safeframe.googlesyndication.com/safeframe/1-0-37/html/container.html

All the same, these two worlds remain bright and beautiful throughout October, plus they appear highest up for the night at nightfall.

If you have a telescope, it’s best to use it when Jupiter and Saturn are highest up for the night at nightfall and early evening. These two worlds will be sinking westward as nighttime deepens, so catch them at early-to-mid evening. Typically, the view of Jupiter’s four major moons and Saturn’s glorious rings through the telescope is sharper when these worlds are higher up than lower down. The thickness of the Earth’s atmosphere near the horizon tends to blur the view of Jupiter’s moons and Saturn’s rings.

Positions of Jupiter’s moons via Sky & Telescope

Look first for brilliant Jupiter; Saturn is the bright object immediately to Jupiter’s east. Although Saturn is easily as bright as a 1st-magnitude star – as bright as the brightest stars in our sky – the ringed planet can’t compete with the the king planet Jupiter, which outshines Saturn by some 13 times. After all, Jupiter almost always ranks as the fourth brightest celestial object, after the sun, the moon and the planet Venus, respectively (although Mars will temporarily reign as the fourth-brightest celestial body – and Jupiter as the fifth-brightest – in October 2020).

For the first time since the year 2000, Jupiter and Saturn will exhibit their great conjunction in December 2020, for the closest coupling of Jupiter-Saturn conjunctions on the sky’s dome since the year 1623. Astronomers use the word conjunction to describe meetings of planets and other objects on our sky’s dome. They use the term great conjunction to describe a meeting of the solar system’s two biggest planets, Jupiter and Saturn. The last great Jupiter-Saturn conjunction was May 28, 2000. The next one will be December 21, 2020. But October 2020 presents a fine time to start watching these worlds.

Watch for the moon in the neighborhood of Jupiter and Saturn for several days, centered on or near October 22.

Mars rises over your eastern horizon by early evening in early October, and coming up earlier daily, heading for its own opposition on October 13, 2020. This month, in October 2020, Mars actually supplants Jupiter as the sky’s fourth-brightest celestial body, after the sun, moon, and the planet Venus. You won’t want to miss this fiery red object lighting up the nighttime sky from dusk till dawn!

In October 2020, Mars exhibits its brightest performance until September 2035. Earth is now rushing along in its smaller, faster orbit, gaining on Mars, the fourth planet outward from the sun. Throughout the first half of October, watch for Mars to brighten as Earth closes in on Mars, passing between it and the sun on October 13, 2020.

Around the world, Mars rises roughly an hour after sunset in early October, around sunset in mid-October, and is up before sunset by the month’s end.

Let the moon help guide your eye to Mars for several nights centered on or near October 2, and then watch again for another several nights in late October, centered on or near October 29.

3 dots lined up across photo, crescent moon in deep blue sky above telephone lines before sunup.

View at EarthSky Community Photos. | From Paul Armstrong, who took this photo of Mars, Saturn and Jupiter on the morning of April 15, 2020, from Exmoor, U.K. Jupiter is at the upper right, Mars at center left, with Saturn between them. In May 2020, Jupiter and Saturn were closer together, whereas Mars was farther away from Jupiter and Saturn. Thanks, Paul!

Venus – the brightest planet – reached its greatest elongation from the sun in the morning sky on August 12 or 13 (depending upon your time zone). But dazzling Venus will remain bright and beautiful as a morning “star” for the rest of this year.

At mid-northern latitudes, Venus rises about 3 1/2 hours before the sun in early October, tapering down to about 3 hours by the month’s end.

At and near the equator, Venus rises 2 1/2 hours before the sun in early October, decreasing to 2 hours at the month’s end.

At temperate latitudes in the Southern Hemisphere, Venus rises about 1 2/3 hours before the sun in early October, tapering to 1 1/2 hours by the month’s end.

Diagram showing positions of Venus in orbit and its phases at inferior and superior conjunction.

Inferior conjunction – when Venus sweeps between the sun and Earth – happened on June 3, 2020. Some 10 weeks later, Venus reached its greatest elongation in the morning sky on August 13, 2020 (when its disk was about 50% illuminated by sunshine). In October 2020, Venus will start the month about 72% illuminated and then end the month about 81% illuminated. Image via UCLA.

Throughout October, Venus in its faster orbit around the sun will be going farther and farther away from Earth. As viewed through the telescope, Venus’ waxing gibbous phase will widen, yet its overall disk size will shrink. Venus’ disk is 72% illuminated in early October, and 81% illuminated by the month’s end; Venus’ angular diameter, on the other hand, will shrink to about 85% of its initial size by late October.

Watch for the waning crescent moon to shine with Venus in the morning sky for several days, centered around October 13 or 14.

Mercury showcases a fine evening apparition during the first week of October 2020 in the Southern Hemisphere. Mercury reaches its greatest evening elongation from the sun on October 1, 2020, and remains a whopping 25 degrees east of the sun until October 7, 2020. Even so, Mercury sits too close to the afterglow of sunset to be visible at northerly latitudes. Mercury shifts out of the evening sky and into the morning sky during the second half of October, and might become visible in the morning sky from northerly latitudes by late October.

Read more: Mercury in the west after sunset

silhouette of a man against the sunset sky with bright planet and crescent moon.

What do we mean by bright planet? By bright planet, we mean any solar system planet that is easily visible without an optical aid and that has been watched by our ancestors since time immemorial. In their outward order from the sun, the five bright planets are Mercury, Venus, Mars, Jupiter and Saturn. These planets actually do appear bright in our sky. They are typically as bright as – or brighter than – the brightest stars. Plus, these relatively nearby worlds tend to shine with a steadier light than the distant, twinkling stars. You can spot them, and come to know them as faithful friends, if you try.

Skywatcher, by Predrag Agatonovic.

Bottom line: October 2020 presents 4 of the 5 bright solar system planets in the evening sky (Mercury only nominally so at northerly latitudes). Catch Jupiter and Saturn at nightfall, Mars at early evening, and Venus in the predawn/dawn sky.