Shine On, Shine On...
The Harvest Moon is the full Moon usually associated with September, so why is the full Moon in October being given that name? That's because September's full Moon occurred on September 1, and the name Harvest Moon is reserved for the full Moon occurring nearest the Autumnal equinox, which was 21 days later, on September 22. The full Moon of October, on the other hand, is closer to the equinox, being only nine days later, on October 1.
On October 13, Mars reaches opposition, meaning that it and the Sun are exactly opposite each other as seen from Earth, with Mars rising at sunset and setting at sunrise. This is also when Mars is closest to Earth, so it looks largest and brightest through telescopes (although still tiny—it's 39 million miles away, after all). Certain features can be seen at this time, such as the growing and shrinking polar ice caps and the sometimes planet-wide dust storms that occasionally obscure the surface.
Various space agencies also launch robotic missions to the Red Planet roughly around opposition to minimize travel time and fuel costs, and three spacecraft from the United States, China, and the United Arab Emirates are currently en route, scheduled to arrive in February.
Tears of the Hunter
The peak of the annual Orionid meteor shower occurs on the night of October 20-21. Active from October 2-November 7, when Earth passes through the trail of dust left in the path of Halley's Comet. As the dust particles rain through the atmosphere and burn up, they're seen as brief streaks of light that appear to radiate from the stars of Orion the Hunter, hence the name of the display. Under ideal conditions (a moonless sky and viewed after midnight from a dark, rural observing site), this shower averages a moderate 10-20 meteors per hour. This year's peak coincides with a waxing crescent Moon that sets before midnight, so moonlight shouldn't interfere during the optimal viewing window between midnight and morning twilight, when Orion is low in the east.
METEOR-WATCHING TIPS (also applies to Leonid and Gemind showers below): Meteor-hunters should allow at least 20 minutes for proper dark adaptation and not look at any bright lights or mobile devices while viewing. Pick a dark spot with a wide-angle view of the sky and as few obstructions such as buildings or trees as possible. Get comfortable and prepare to observe for at least a couple of hours. Don't expect a steady stream of meteors, as they might occur in bursts, and don't look just toward the radiant or the constellation after which the shower is named, or you'll catch only brief, foreshortened streaks. To see longer meteor streaks, look away from the radiant so that the meteors are crossing your line of sight.
A Blue Moon (or Should That Be "Boo" Moon?)
The second full Moon in the same calendar month—such as the one occurring on Halloween night, October 31—has come to be called a blue Moon. However, that's only one usage of the term, and it's the result of a 1946 editorial error in the interpretation of an older definition (in use since at least 1819) which defined a blue Moon as the third full Moon during a season that has four full Moons—and the next time we'll see one of those, according to the older meaning, is on August 22, 2021. In either case, both definitions apply to yet a third and even older usage of the term, which simply describes something that's rare ("once in a blue Moon"). In none of these cases, however, does the Moon ever really appear blue-colored.
The Lion's Fiery Roar
Active November 6-30, when Earth passes through the dusty path of Comet Tempel-Tuttle, the Leonid meteor shower peaks during the predawn hours of November 17. This display is historically important because of its "storm"-level activity every 33 years, producing 1000 meteors per hour.
Presently about midway between storms—the last one having been in 2002—the shower is weak to moderate, averaging about 15 meteors per hour as seen from dark locations and clear, moonless conditions. The waxing crescent Moon sets soon after sunset on the 16th, assuring a dark sky for meteor shower observations. By midnight, the Zodiacal constellation Leo the Lion, from which the meteors seem to radiate, is rising in the east-northeast. See METEOR-WATCHING TIPS above.
A Pale Shadow of an Eclipse
On the night of November 29-30, a penumbral lunar eclipse occurs as the Moon passes through the very faint outer portion of Earth's shadow, or penumbra. As seen from San Francisco, the Moon enters the penumbra at 11:32 pm on the night of the 29th, reaching maximum at 1:42 am, when a very faint shading might be perceptible across its northern half. The Moon exits the penumbra at 3:53 am. Remember that this type of eclipse is difficult to observe and can easily be missed by casual viewers if they're not aware that one is happening.
The Year's Best Meteor Shower?
From December 4-17, Earth's orbit carries it through the dust trail of rock-comet 3200 Phaethon, producing the annual Geminid meteor shower. At its peak on December 13-14, the Geminids are considered the most reliable of the major displays, producing 80-100 meteors per hour under ideal locations. Many people aren't as familiar with the Geminids as they might be with the more famous Perseids of August, which have the advantage of taking place during the warm summer season. This year, the Geminids peak during a new Moon, so weather permitting, observers braving the chill of a December night should see a fine show. Be sure to check METEOR-WATCHING TIPS above!
A Southern Solar Eclipse
On December 14, the full Moon passes between Earth and the Sun, casting its shadow onto the surface of our planet. Observers along the path of the roughly 150-mile wide shadow will see a total lunar eclipse in which the Sun becomes completely hidden from view. This time around, the shadow falls mostly across the southern Pacific and Atlantic Oceans, making landfall only across the narrow southern part of South America, cutting across Chile and Argentina more or less along the south 40th parallel.
Skywatchers with proper eye protection will see the Moon slowly cover the Sun, eventually covering its disk completely and briefly revealing our star's faint outer atmosphere, or corona. This period, called totality, will last only about two minutes, and may also be viewable from ships at sea that are along the shadow-path. Observers in other parts of South America, the Antarctic Peninsula, and the coast of Queen Maud Land in Antarctica will see only a partial solar eclipse. No part of this eclipse will be visible from the United States.
Fun Facts about the Winter Solstice (December 21)
- Through the year, observers can see sunrise and sunset move back and forth along the horizon, from a northernmost point in the summer to a southernmost point in the winter. The day the motion stops and reverses is called the solstice ("Sun standing still").
- As seen from Earth's northern hemisphere, the Sun appears to rise and set farthest south, following a very low arc that is above the horizon for the shortest amount of time for the whole year.
- On the winter solstice, Earth's north pole is tipped away from the Sun by the greatest amount (23.5 degrees). In fact, the north pole itself is in constant darkness and never sees the Sun.
- The Sun's light strikes the northern hemisphere at a shallower angle, reducing the amount of heat received at the surface, and across the northern hemisphere, temperatures drop. This is commonly considered the beginning of winter, whereas in the southern hemisphere, where the seasons are reversed, the December solstice marks the beginning of summer.
Quite a Sight for a Yuletide Night
A holiday treat for stargazers on the solstice (and during the few days before and after) is the early-evening sight of the planets Jupiter and Saturn in the sky. These giant worlds have been ponderously inching together against the stars of Sagittarius and Scorpius all year, and that motion culminates on December 21, when the two are separated by only 1/10 of a degree of arc—that's 1/5 the apparent diameter of a full Moon. Anyone with sharp eyesight or binoculars should be able to resolve the two, but for those with a bit less acuity, the two might seem to merge into a single, bright point of light!
Download the Morrison Planetarium's 2020 Pocket Almanac to stay up-to-date on eclipses, meteor showers, satellite spottings, and more.