The month of October always marks the first full month of fall for us in the northern hemisphere. The nights are getting considerably longer and cooler now, which also allows our famous New England fall foliage to blaze forth in all of its wide range of vibrant colors.

Just as with the change in seasons in the northern hemisphere, the celestial vault above our limited terrestrial view is being transformed. The top of the Winter Hexagon begins to appear once again over our eastern horizon before 10 p.m., and we say goodbye to summer as Scorpius and Sagittarius disappear below our southwestern horizon. Notice that any given star will rise four minutes earlier each night, so that the whole sky seems to move ahead two hours each month. The sky will look the same at 8 p.m. on Nov. 1 as it does on Oct. 1 at 10 p.m.

There are many interesting highlights in October, such as Jupiter still being very close to its Sept. 26 opposition. That marked its closest approach to Earth since 1963. It will reach minus 2.9 magnitude, only 6 times fainter than Venus at its best at minus 4.9 magnitude. Saturn still looks bigger and brighter than usual since it just reached opposition on Aug. 14. Mars is getting bigger and brighter and closer every night now, approaching its Dec. 8 opposition.

The annual Orionid meteor shower peaks on Oct. 21 with no moon to interfere until 3 a.m. The moon will occult Uranus on Oct. 12 and Mercury on Oct. 24. The second largest asteroid, Vesta at 320 miles in diameter, or about the size of Arizona, will reach 7th magnitude and be easily visible in a pair of binoculars in Capricorn near Saturn. There will be several nice conjunctions of the moon with the planets, as usual, but since we are in a new eclipse season now, there will be a partial solar eclipse over Europe, parts of Asia and northern Africa. It will reach 80% of total over parts of Russia, but no part of it will be visible for us. However, we will be able to see a total lunar eclipse two weeks after that time on Nov. 8 early in the morning, just as the moon will be setting.

Jupiter is in the western part of Pisces the Fish now, just below the circlet of six stars. Since it takes Jupiter 12 years to orbit the sun, it will spend one full year in each of our 12 zodiac constellations along the ecliptic. That includes its annual retrograde loop, when it appears to be moving backwards or westward against the fixed background of stars in our sky for four months. It will remain in retrograde until Nov. 23. There will be several nice transits of its largest moons across the face of Jupiter visible in a telescope this month. I have seen that many times and it really gives you a good insight into the motions of this miniature solar system. Their orbits range from two to 16 days and some of them change noticeably in just a few minutes when they are close to the planet. Its four largest moons, also called the Galilean moons since he discovered them just over 400 years ago, are visible in just a pair of binoculars. Jupiter has at least 79 moons, only 53 of which are officially named.

Saturn is still providing us with above average views in the eastern part of Capricorn. You can see it about 30 degrees to the right and slightly above Jupiter. It shines with a slightly golden light at 0.5 magnitude, or about 15 times fainter than Jupiter. Saturn takes 30 years to orbit the sun, so it will spend just over 2 years in each zodiac constellation along with two retrograde loops. The ringed planet will end its retrograde motion on Oct. 23, just nine weeks after its opposition occurred on Aug. 14. Saturn has 82 moons, only 53 of which are named.

Mars is getting bigger and brighter and closer to us each night as Earth is rapidly catching up with the red planet in our orbits around the sun. Mars orbits at 15 miles per second while the earth averages 18.6 miles per second, so we catch up with and pass our neighbor every 26 months. That will happen again on Dec. 8. Mars now looks like a brilliant imposter in the familiar Winter Hexagon. It can be found in the middle of Taurus, forming a stunning triangle with two other red objects, Aldebaran in Taurus and Betelgeuse in Orion. Compare the brightness and color of these three objects and you will see that Mars is the brightest and reddest and will keep getting brighter until Dec. 8, while the two stars will remain at about the same brightness since they are both slightly variable stars.

The Orionid meteor shower will take place from Oct. 2 through Nov. 7, but it will peak on Friday morning Oct. 21. Its radiant in Orion will rise at 10:30 p.m. and the waning crescent moon will not rise until 3 a.m. You can expect about 20 meteors per hour from a dark sky site with no light pollution from any towns.

There will be a partial solar eclipse at new moon this month on Tuesday, Oct. 25. It will reach its maximum of about 80% over parts of Russia. Remember that a total solar eclipse will pass right over Maine on April 8, 2024, just before the second Artemis mission is scheduled to fly to the moon with humans aboard, but they will not land on the moon until their third mission around 2025. Then we may be walking around on Mars by 2037.

OCTOBER HIGHLIGHTS

Oct. 1: In 1897, the 40-inch refractor at the Yerkes Observatory was dedicated and became the largest telescope in the world. It is still the largest refractor in the world. George Ellery Hale designed it along with the next three largest telescopes in the world, culminating in the 200-inch reflector at Mt. Palomar in 1948.

Oct. 2: First quarter moon is at 8:14 p.m.

Oct. 4: The moon is at perigee, or closest to Earth today at 229,488 miles. In 1957 the Russians launched Sputnik 1 and began the Space Age and the Space Race.

Oct. 5: The moon passes 4 degrees south of Saturn tonight.

Oct. 7: The asteroid Vesta is stationary and at its best in Capricorn near Saturn tonight.

Oct. 8: The moon passes two degrees south of Jupiter tonight. Pluto is stationary, ending its retrograde motion in Capricorn. Since it takes 248 years to orbit the sun once, Pluto spends nearly 21 years in each zodiac constellation.

Oct. 9: Full moon is at 4:55 p.m. This is also called the Hunter’s Moon. The German astrophysicist Karl Schwarzschild was born in 1873. He calculated the event horizon for black holes using Einstein’s field equations.

Oct. 15: The moon passes 4 degrees north of Mars tonight. The American astronomer Asaph Hall was born on this day in 1829. He discovered the moons of Mars – Phobos and Deimos – in 1877.

Oct. 17: The moon is at apogee or farthest from Earth today at 251,238 miles. Last quarter moon is at 1:15 p.m.

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

Oct. 22: Venus is in superior conjunction and will not be visible for a while until it becomes an evening planet next month. Karl Jansky was born in 1905. He is the father of radio astronomy and he first found radio signals from the center of our Milky Way galaxy.

Oct. 23: Saturn is stationary, ending its retrograde motion in Capricorn.

Oct. 25: New moon is at 6:49 a.m.

Oct. 30: Mars is stationary, beginning its retrograde motion leading to its opposition on Dec.8.

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

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