This is the first full month of autumn, and it will bring with it a radical transformation of our lush green summer landscape into the dramatic and memorable flaming foliage of fall for which New England is so famous. This is also a great time to get outside under the night sky to experience more of its ongoing and completely natural wonders.

We tend to have more clear nights this month than during other months, and they tend to be cool and crisp as our summer humidity disappears and the Earth tilts farther away from the sun, making our days shorter and shorter and our nights longer and longer.

SKY GUIDE: This chart represents the sky as it appears over Maine during October. The stars are shown as they appear at 10:30 p.m. early in the month, at 9:30 p.m. at midmonth and at 8:30 p.m. at month's end. Mars is shown in its midmonth position. To use the map, hold it vertically and turn it so that the direction you are facing is at the bottom. Sky chart prepared by George Ayers

There will be several highlights this month that will be well worth watching, including the return of Jupiter and Mercury to our morning sky; Venus catching up with and crossing under Saturn in Scorpius; Uranus at opposition in Pisces along with the dwarf planet Ceres; the moon occulting Aldebaran in Taurus; comet 43P/Wolf-Harrington in Hydra; asteroid Parthenope in Cetus the Whale; and the Orionid meteor shower caused by Halley’s Comet.

Jupiter returns to our morning sky after disappearing near the sun for a month. Look for the king of the planets just 1.6 degrees below Mercury on the morning of Oct. 10. The next morning they will be even closer together, and then Jupiter climbs higher even as Mercury sinks lower again.

Venus continues to climb a little higher and move 1 degree east per day. Watch as a slender waxing crescent moon passes just above Venus on the evening of Oct. 3, half an hour after sunset. Then, keep watching as Venus will shoot the gap between Saturn and Antares in Scorpius, just like Mars did on Aug. 23. Venus will pass just 3 degrees below Saturn in this lineup on Oct. 29 and 30. You can think of this like a giant slingshot in space. They only appear that way from our perspective on Earth, but it is a good chance to think more carefully about the motions of these three objects and what they are really like up close.

Venus is sometimes called our sister planet because it is nearly the same size and mass as Earth, but that is where the similarities end. Venus exhibits the classic runaway greenhouse effect, with a surface temperature of 900 degrees, hot enough to melt some metals, and a surface pressure nearly 100 times greater than we experience on Earth. The pressure on the surface of Venus is equivalent to being 3,000 feet below the surface of our ocean. Venus orbits at 22 miles per second and takes 225 days to get around the sun. It spins so slowly that its day is longer than its year, at 243 Earth days. It also spins in the opposite direction of Earth, since its axis is flipped over. The sun would rise in the west on this incredibly dangerous planet.

There are several new missions now being proposed that will revisit this planet and see it in much better detail to uncover a few more of its important mysteries that will also help us understand Earth better. NASA is in the process of deciding between Veritas, which would remain in orbit around Venus like the Magellan spacecraft that arrived in 1990, and Davinci, which would drop a probe onto its surface.

If you have a good pair of binoculars, you can find the planet Uranus in Pisces. It is at opposition on Oct. 15. That means it rises at sunset and stays in our sky all night long and is at its closest and brightest for the year. Once you spot its eerie blue-green glow in your binoculars, you should be able to see it without them, since it will glow at 5.7 magnitude. The faintest objects the unaided human eye can see in a dark sky are at sixth magnitude, which is a little fainter than 5.7 magnitude.

Ceres, the largest of our millions of asteroids, is also at opposition now in Pisces. This 600-mile-wide dwarf planet will shine at 6.7 magnitude, so you would need binoculars or a telescope to see it. We recently found mysterious white spots in one of its craters.

The waning gibbous moon will occult Aldebaran, the brightest star in Taurus, on the night of Oct. 18 into Oct. 19. Check the website on lunar occultations for more details. I have seen similar events several times, and it is a great way to get a sense of the moon’s second-by-second eastward motion around the earth as it moves right in front of a bright star, causing it to disappear instantaneously not to reappear until one hour later.

Comet 43P/Wolf-Harrington will be visible in a telescope in Hydra this month. It should reach around 11th magnitude in our morning sky. It is part of Jupiter’s family of periodic comets. We haven’t had many bright comets lately, but that should end soon with brighter comets scheduled to visit us in December and January.

The asteroid named Parthenope, after a siren of the sea in Greek mythology, will be at its best in Cetus the Whale near Uranus and Ceres this month. This 100-mile-wide main-belt asteroid orbits between Mars and Jupiter at about 6 miles per second relative to Earth, which is about the speed that Saturn orbits the sun. It will only reach ninth magnitude, so you would need a telescope to see and appreciate this large chunk of metallic nickel-iron with magnesium and iron silicates. While looking at this asteroid in a telescope you could also see some of the geosynchronous satellites that always orbit the earth at 22,300 miles high. Some of them will reach fourth magnitude in October. Once you find one, turn off the drive on the telescope and you can keep watching it, since geosynchronous satellites always stay over the same spot above the Earth as we spin on our axis at about 700 miles per hour at this latitude.

The Orionid meteor shower peaks on the night of Friday, Oct. 21, into Saturday morning. Unfortunately, the last quarter moon will rise around midnight to spoil some of the show. Try to catch some meteors before that happens, or face west in the sky to get away from the rising moon. You can expect about 15 meteors per hour, tiny sand grain-sized particles of Halley’s Comet. These meteors are all caused by the Earth moving through the debris trail of Halley’s Comet. This famous comet also causes the Eta Aquarid meteor shower every May 4. You could also look for a lesser shower, the Southern Taurids, caused by Comet Encke on Oct. 10.

OCTOBER HIGHLIGHTS

Oct. 1: In 1897, the Yerkes 40-inch refractor was dedicated. Designed by George Ellery Hale, it was the largest telescope in the world at the time. Hale also designed the next three large telescopes, each of them the largest in the world at the time. His last one was the 200-inch reflector at Palomar Mountain in California in 1948.

Oct. 3: The moon passes near Venus.

Oct. 4: In 1957, Sputnik 1 was launched, marking the start of the space age.

Oct. 6: The moon passes 4 degrees north of Saturn.

Oct. 7: In 1885, Niels Bohr was born. He was one of the pioneers in the quantum mechanics revolution, which made a lot of our modern technology possible.

Oct. 8: The moon passes near Mars.

Oct. 9: First quarter moon is at 12:33 a.m. Kepler’s supernova was seen on this day in 1604.

Oct. 15: The planet Uranus is at opposition in Pisces, reaching 5.7 magnitude.

Oct. 16: Full moon is at 12:23 a.m. This is also called the Hunter’s Moon.

Oct. 21: Dwarf planet Ceres is at opposition in Pisces. The Orionid meteor shower peaks.

Oct. 22: Last quarter moon is at 3:14 p.m.

Oct. 25: Venus passes 3 degrees north of Antares in Scorpius.

Oct. 28: The moon passes near Jupiter this morning.

Oct. 30: New moon is at 1:38 p.m.

Oct. 31: In 2005, the Hubble Space Telescope discovered two new moons of Pluto.

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

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