October is the first full month of autumn in the northern hemisphere and usually a great time to get outside and enjoy the many wonders of the night sky before it gets considerably colder.

The wonderful foliage is transforming our landscape on earth, just as our celestial landscape marches on inexorably toward another winter. We will soon lose some summer constellations like Scorpius and Sagittarius, where Jupiter and Saturn are dwelling. To replace them, we will gain Auriga and Taurus, the top part of the Winter Hexagon. All of Orion will not rise until midnight, but by next month it will be prominent by 10 p.m., signaling that winter is once again on our doorstep.

This month has many interesting highlights including six planets visible in the evening sky; the return of both of our celestial next door neighbors, Venus and Mars; several nice conjunctions of the moon with the planets; and two meteor showers.

Two of those six planets will require binoculars or a telescope to see, but it is nice to know where they are. Uranus is at opposition on the 27th in the constellation of Aries. It will get as bright as 5.7 magnitude; for an object to be visible without optical aid, it must have a magnitude of 6.0 or more. Though I have never seen this planet without optical aid, it is technically possible from a dark sky site.  William Herschel discovered Uranus on March 13, 1781. It was the first planet discovered with a telescope. It was originally named Planet George, after Great Britain’s King George III, but was soon renamed to Uranus, after the Greek god of the heavens and the father of the Titans of Greek mythology.

It takes 84 years for Uranus to complete one orbit around the sun, and it is tilted on its side 90 degrees with respect to the ecliptic plane. It rotates the opposite way of all the other planets except for Venus, which also rotates from east to west. Consequently, on these two planets, the sun rises in the west. Uranus has 27 moons and 13 distinct rings, which are different from the rings of all the other gas planets. Some of its rings are 77 Kelvin, or minus 321 degrees F, which is the boiling point of nitrogen, when it turns from a liquid into a gas. The surface of this gas giant planet is even colder, only 47 Kelvin. Its rings were only discovered recently, in March of 1977, nearly 200 years after the planet itself was discovered.

The other faint planet now visible in the evening sky is Neptune, our eighth and last planet, at least for now. Neptune is in Aquarius and was at opposition last month. It takes 165 years for it to complete one orbit. Neptune was discovered on September 23, 1846 by three people. It’s astounding to realize that it has completed only a little more than one orbit since its discovery.

Jupiter continues to set a little earlier and travel a little farther away from us each evening. By the end of this month, it will set just 2  1/2 hours after sunset. It is still in Scorpius and is moving in its normal, prograde or eastward motion against the background of stars. Watch the waxing crescent moon pass just to the left of Jupiter on the evening of October 3.

Saturn is about two hours behind Jupiter and one constellation to the east, or left of Jupiter. The ringed planet will reach about 30 degrees high in our South-Southwestern sky 45 minutes after sunset. It will reach eastern quadrature on October 7, which means that its shadow is cast farthest to the side, giving it its most three-dimensional appearance. It is also moving in direct motion now, and it will set around 10 p.m. by the end of the month. The first quarter moon will be just to the left of Saturn on the evening of the fifth.

Venus will reappear in our evening sky after a long absence. We last saw it on July 21 in the morning sky before it went to superior conjunction with the sun when it is fully illuminated but farthest away at the same time. Look for it low in the western sky right after sunset. Even by the end of the month, Venus will only set one hour after sunset. Mercury will be near Venus in the evening sky all month. On the 19th, it will reach its greatest eastern elongation of 25 degrees from the sun. Next month it will transit the sun — standby for more information.

Mars is reappearing in our morning sky in the constellation of Virgo after an equally long absence from our evening sky — since the middle of July. The red planet will rise nearly two hours before the sun by the end of the month. Mars is quite far away right now, over 2 1/2 times our average distance to the sun, but by next year at this time when Mars reaches opposition, its disk will appear six times larger in our sky. The northern hemisphere of Mars will experience its summer solstice on October 7.

The Southern Taurid meteor shower will peak on October 10.  It is a minor shower caused by Comet Encke, which has the shortest period ( 3.3 years) of any known periodic comet. Even at its peak, it will reach only five meteors per hour, but it is known to generate some brilliant fireballs that can get brighter than the full moon.

The more famous Orionids will peak on the 21st. Those are caused by the earth passing through the debris trail of Halley’s Comet. That comet also creates the Eta Aquarid Meteor Shower every May when we pass through this famous comet’s inbound path. The moon will be full on the 13th of this month, so that means that the moon will be last quarter and rising around midnight to spoil the rest of this show on Monday the 21st. You can expect about 20 meteors per hour at its peak, all emanating from the constellation of Orion, which will rise by 11 p.m. that night.

OCTOBER HIGHLIGHTS

Oct. 1: The Yerkes Observatory in Wisconsin was dedicated on this day in 1897. Designed by George Ellery Hale, its 40-inch refractor was the largest telescope in the world at the time, and even now is the largest refractor in the world. The largest telescope in the world today is a reflector on the Canary Islands, which measures 34 feet (409 inches) in diameter. Three much larger reflecting telescopes are being designed now, one of which will be nearly 40 meters across, over three times larger than that on the Canary Islands. Maria Mitchell, the first professional female astronomer in the United States, discovered a comet on this day in 1847.

Oct. 3: The moon and Jupiter will be just one and a half degrees apart this evening.

Oct. 4: The Russians launched Sputnik on this day in 1957, essentially beginning the space age and the space race.

Oct. 5: The moon and Saturn are just 2 degrees apart this evening. First quarter moon is at 12:48 p.m.

Oct. 10: The Southern Taurid Meteor shower will peak tonight.

Oct. 13: Full moon is at 5:09 p.m. EDT. This is also called the Hunter’s Moon.

Oct. 16: The moon will pass below the Pleiades and above Aldebaran in Taurus tonight.

Oct. 21: The Orionid Meteor Shower will peak tonight. Last quarter moon is at 8:40 a.m. Watch the moon pass below Castor and Pollux in Gemini one hour before sunrise.

Oct. 26: A very thin waning crescent moon will pass just above Mars half an hour before sunrise this morning.

Oct. 27: New moon is at 11:40 p.m.

Oct. 31: On this day in 2005 the Hubble Space Telescope discovered Nix and Hydra, two more moons of Pluto. It would discover Kerberos in 2011 and Styx in 2012. These four moons are only 20 to 30 miles across and they tumble chaotically around Pluto and Charon, which are 1,500 miles and 750 miles in diameter, respectively.

Bernie Reim of Wells is co-director of the Astronomical Society of Northern New England.