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 that are especially needed in today’s hectic times on Earth. We sometimes forget that we are all important parts of this continually unfolding and changing natural drama of our greater environment about which we know so little.

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 great Earth tilts farther away from the sun as our days get shorter and shorter and our nights get longer and longer.

There will be several interesting 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 occults 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 the 10th. The next morning, they will be even closer together, 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 the 3rd 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 the 23rd of August.

Venus will pass just 3 degrees below Saturn in this line-up on the 29th and 30th of this month. You can think of this like a giant sling-shot in space. That only appears that way from our Earth perspective, 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 we are, but that is where the similarities end. Venus exhibits the classic runaway greenhouse effect, with a surface temperature of 900 degrees F – hot enough to melt some metals – and a surface pressure of 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 from 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 again 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 the 15th. 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 all 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 the 18th into the 19th. 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 good 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 and not 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 should 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 them, because they 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 showers peaks on Friday night the 21st 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 the 10th.

Oct. 1: On this day 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. He also designed the next three large telescopes, each one the largest in the world at the time. His last one was the 200-inch reflector at Mt. Palomar in 1948.

Oct. 3: The moon passes near Venus this evening.

Oct. 4: On this day in 1957, Sputnik 1 was launched, marking the start of the Space Age.

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

Oct. 7: On this day 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 tonight.

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 tonight, 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 tonight 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: On this day in 2005, the Hubble Space Telescope discovered two new moons of Pluto.


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