October always marks the first full month of fall for us in the northern hemisphere. As you watch the transformation of the landscape through the emergence of New England’s flaming foliage, be aware that the skies are also slowly transforming, letting us know winter isn’t far ahead.

The winter hexagon is now beginning to rise before 9 p.m. and this entire group of the brightest stars of the winter sky will have cleared the horizon by midnight by the end of this month, letting us peer right into a window in the sky, revealing some bright winter constellations that foretell what our sky will look like throughout the next season. You can also view this same winter hexagon in August, but would have to be up at 4 a.m. to see it.

The highlights this month include the breakup of the great planetary lineup of the four brightest planets in our evening sky for most of the summer, since a very brilliant Mars joined the other three in late July. We will lose Venus by the first week of this month, but it will pop back up again in our morning sky by the end of the month. There will be several nice conjunctions as usual, but there will also be another potentially bright comet and two meteor showers.

The other three bright planets will hang on a little longer, but the next two in sequence, Jupiter and Saturn, will sink below our western horizon before midnight as the earth pulls farther ahead of them. Jupiter in Libra will set just one hour after sunset by the end of the month. Then Saturn in Sagittarius will set by 9 p.m., or three hours after sunset, by the end of the month.

I well remember seeing the seven largest of Saturn’s 62 moons through a large 18-inch reflecting telescope from the top of Mt. Cadillac recently before it was even completely dark and before the masses of people joined us at the top for marvelous views of the Milky Way, the great planetary lineup and dozens of other denizens of the night sky that always reside just beyond our vision. Those moons range from Titan at 3,000 miles in diameter, bigger than Mercury and twice as large as Pluto, down to Mimas at 250 miles across.

Each of those little orbiting dots clustered together in the telescope were in reality extremely different and unique alien worlds, one billion miles away, or about 84 minutes at the speed of light. Iapetus is half white and half dark, Mimas has a huge crater one third of the size of the moon, and the strangest and potentially the most exciting of the bunch, since it well have life on or just under its surface, is Enceladus.

About a dozen giant plumes of water vapor and ice were discovered erupting from its south pole by the Cassini mission before we crashed it into Saturn last September. The signature of complex organic molecules has been spotted in these plumes and methane has been found on its surface. Its subsurface salty ocean could be teeming with at least microscopic life, a mere 84 minutes away at the speed of light.

Mars will hang around the longest because it’s the easternmost planet in this great lineup. It will get twice as dim again by the end of this month as Earth pulls well ahead in our faster orbit around the sun. But it’s still much brighter than usual and you can still see some nice features on its surface through a good telescope.

Look for a waxing crescent moon above Jupiter on the 11th and close to Saturn on the 14th. Then keep watching as the moon catches up with Mars in the middle of the triangle that marks Capricorn on the night of the 17th.

This month’s featured comet will be 38P/Stephan-Oterma. Last month it was Giacobini-Zinner in Auriga and the month before it was PanSTARRS in Cassiopeia. 38P was discovered in 1867 in France, then rediscovered by Liisi Oterma in Finland in 1942. Oterma was the first woman to receive a PhD in astronomy in Finland. You can see her comet now in Orion just above and to the left of its most famous star, the red supergiant named Betelgeuse. You will need a good pair of binoculars or a small telescope to see it since it’s only expected to get to about 10th magnitude, or 40 times fainter than what you could see with the naked eye. Orbiting the sun every 38 years, this is a fairly short period comet. Halley’s Comet orbits every 76 years and won’t show up again until 2062.

The first meteor shower for this month is the Draconids on the 8th. This shower doesn’t usually produce much more than the background rate of five or so meteors per hour, but it could be much better this year since its parent comet, Giacobini-Zinner, just reached perihelion and perigee last month. There will be no moon to interfere, so look toward the north in the constellation of Draco the Dragon to see these meteors.

Then the next shower, which is much more famous than the Draconids, are the Orionids that peak on the 21st. Caused by Halley’s Comet, you can expect up to 20 meteors per hour. The moon will be waxing gibbous, just three days before full, so it will interfere with this shower until setting at 3:30 a.m. Meteor showers are usually much better after midnight. Look toward the constellation of Orion high in the sky by this time of the morning. You will see tiny pieces of Halley’s Comet burning about 70 miles high in our atmosphere as we pass through its debris trail at 67,000 miles per hour. We will also pass through Halley’s Comet’s trail again on May 4, also known as the Eta Aquarid Meteor Shower. This is the only comet that creates two meteor showers for us each year.

OCTOBER HIGHLIGHTS

Oct. 1: The 40-inch refractor at the Yerkes Observatory on Lake Geneva in Wisconsin was dedicated on this day in 1897. Designed by George Ellery Hale, this was the largest telescope in the world at the time and it is still the largest refractor in the world.

Oct. 2: Last quarter moon is at 5:47 a.m.

Oct. 4: The thin waning crescent moon and the Beehive star cluster rise together in the eastern sky before sunrise. On this day in 1957 the Soviet Union sent the first ever man-made satellite into space, Sputnik 1, thereby beginning the space race.

Oct. 5: Neil DeGrasse Tyson was born on this day in 1958.

Oct. 7: Niels Bohr was born on this day in 1885. He was one of the pioneers of the quantum revolution that makes most of the modern technology that we use every day possible.

Oct. 8: New moon is at 11:48 p.m. The Draconid Meteor shower peaks.

Oct. 9: Kepler’s supernova in Ophiuchus was discovered on this day in 1604.

Oct. 10-16: Look toward the east before dawn and you may see the subtle glow of the zodiacal light. I saw it over the ocean at Acadia National Park a couple of weeks ago.

Oct. 21: The Orionid meteor shower peaks this morning.

Oct. 24: Full moon is at 12:46 p.m. This is also known as the Hunter’s Moon.

Oct. 26: Watch for the waning gibbous moon in the Hyades star cluster in Taurus all night.

Oct. 31: Last-quarter moon is at 12:41 p.m. On this day in 2005 the Hubble Space Telescope discovered the second and third moons of Pluto, Nix and Hydra.

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

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