November is a good transition month between fall and winter. Most of our famous foliage is now past its peak, and the nights are getting longer and colder. The big shock will happen when daylight saving time ends on the third, and we will suddenly be plunged into darkness much earlier than we have become used to. By the end of this month, the sun will set just a few minutes after 4 p.m., and the days will be a little over 9 hours long, not much different from at the winter solstice.

Several rare and interesting highlights this month —well worth watching if the weather cooperates — may make up for some of the extremes we are about to experience. These include a rare transit of our first planet, Mercury, across the face of the sun; an even more rare visit of an interstellar interloper named Comet Borisov; the Leonid Meteor Shower; fully half a dozen planets still visible in our evening sky; a close conjunction between our two brightest planets, Venus and Jupiter; and a bright asteroid named Vesta in opposition in Cetus the Whale.

The last transit of Mercury was on May 9, 2016. Now, just 3 1/2 years later, we will see another one on Nov. 11. Here on the East Coast, it will start at 7:35 a.m. and end at 1:04 p.m. We are perfectly placed to see the whole 5.5 hour event, which, to watch safely, requires a telescope and good solar filter. Most of it will not be that visually exciting, but try to catch at least the very beginning and end. It will take 1 minute and 41 seconds for the full disk of tiny Mercury to completely enter the nearly 200 times larger disk of the sun.

Mercury is only 3,000 miles in diameter, just over a third of the size of Earth. Our solar system has two moons that are larger than Mercury: Ganymede and Titan. It’d be nice to find some sunspots visible on the sun for a good size comparison, but that is unlikely because the sun has been very quiet and inactive for most of this whole year.

Transits of our two inner planets, Mercury and Venus, are an interesting study in math and physics. They can only happen at inferior conjunction with the sun when that coincides with an ascending or descending node as they pass directly between us and the sun, creating a mini eclipse. Mercury’s orbital plane is inclined 7 degrees to the ecliptic and Venus’s is 3 degrees, so most of the time these two planets orbit above or below that plane. All Mercury transits happen in May or November, and all Venus transits happen in June or December.

Venus transits are even rarer, happening in pairs eight years apart with a gap of 105.5 years and then another pair eight years apart and then an even longer gap of 121.5 years. I was very lucky to be able to see both of the last transits of Venus, on June 8, 2004 and June 4, 2012. The next one isn’t until December, 2117. I had expected to see the black drop effect, as the planet seems to stretch out just as it enters or exits the sun, but instead I saw something much more dramatic and memorable. I saw the entire atmosphere of Venus outlined against the blackness of space as a brilliantly glowing semi-circular arc of pure silver light just as Venus was exiting the sun; it took about 15 minutes, much longer than it will take Mercury to exit the sun.

Although they happen 13 times per century, the next transit of Mercury will not occur until Nov. 13, 2032 and the next one visible for us not until 2049, so definitely try to see and photograph this one. If it is clear out, we will have telescopes set up outside the Southworth Planetarium on the Portland Campus of USM. If not, try to watch live feeds of this rare event, which have the benefit of live commentary from scientists, teachers and other astronomers.

A comet named Borisov that came in from another solar system is now near Leo, based on its hyperbolic orbit. It is still getting closer and brighter, but it will reach only 15th magnitude and will require at least a 12-inch telescope to see or photograph. Just two years ago we had another visitor from another solar system, which was probably an asteroid. Named Oumuamua, which means “scout” in Hawaiian, it has already exited our solar system. These events may be much more common than we think, but because these are very faint objects, they are hard to detect.

The annual Leonid meteor shower will peak on Sunday morning the 17th, but the waning gibbous moon will rise by 9 p.m., washing out most of these meteors this year. One of the most incredible astronomical events that I have ever witnessed, other than the total solar eclipse two summers ago in Idaho, was seeing nearly 1,000 Leonids per hour for three hours on the morning of Nov. 18, 2001 from our new observatory in Kennebunk.

Most of the action is still taking place in our evening sky. Both Jupiter and Saturn are still the “stars” of our evening sky, but now Venus and Mercury will be joining the pair of our two largest planets that lingered with us all summer and fall. Watch all month long as Venus catches up with Jupiter. It will get to within just one degree by the 22nd and then pass Jupiter, creating a nice line of three bright planets in our evening sky: Saturn, Venus and Jupiter. During the last few days of this month, watch the thin waxing crescent moon pass by all three.

The planets Uranus and Neptune are still near their best in our evening sky, but you will need a telescope to see them. Mars is the only exception as the lone morning planet now, rising about two hours before sunrise.

The fourth largest asteroid, named Vesta, will reach opposition in Cetus, near Taurus, on the 7th. It will reach 6.6 magnitude, not quite bright enough to be seen without optical aid. At 326 miles in diameter, the size of Arizona, Vesta is not quite round enough or large enough to be classified as a dwarf planet like Ceres and Pluto.

NOVEMBER HIGHLIGHTS

Nov. 1: The waxing crescent moon will be near Saturn tonight and the next night.
Nov. 3: Daylight-saving times ends at 2 a.m. On this day in 1957, the Russians launched Sputnik 2, only a month after they launched the first Sputnik satellite.
Nov. 4: First quarter moon is at 5:24 a.m.
Nov.6: On this day in 1572, Tycho Brahe discovered a supernova in Cassiopeia without a telescope, since that was not invented until 36 years later.
Nov. 8: Edmund Halley was born on this day in 1656. The most famous of all comets is named after him, although he never actually saw it himself, nor did he see any of the Venus transits.
Nov. 9: Carl Sagan was born on this day in 1934. Mars and Spica form a nice pair in the morning sky in Virgo 45 minutes before sunrise.
Nov. 11: Mercury will transit the sun today starting at 7:35 a.m. and lasting until 1:04 p.m.
Nov. 12: Full moon is at 8:36 a.m. It’s also known as the Beaver or Frosty Moon.
Nov. 17: The Leonid meteor shower peaks tonight. Caused by Comet Tempel-Tuttle, you could normally expect about 20 meteors per hour, but the moon will rise by 9 p.m.
Nov. 19: Last quarter moon is at 4:12 p.m.
Nov. 22: Venus and Jupiter will be just over one degree apart tonight 45 minutes after sunset.
Nov. 25: Look for Mars and Mercury in the morning sky along with a thin sliver of a moon.
Nov. 26: New moon is at 10:07 a.m.
Nov. 27, 28, 29: The waxing crescent moon will nicely point out Jupiter, then Venus, and then Saturn in succession over these three evenings about 45 minutes after sunset.

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


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