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(Times are for San Francisco, CA, and will vary slightly for other locations.)
On October 3, Uranus is at opposition. Not usually regarded as a naked-eye planet, Uranus is visible through telescopes as a tiny, pale-green disk. Discovered in 1781 by Sir William Herschel, this planet—4 times Earth’s diameter—was the first to be discovered telescopically. Initially, however, it was mistaken for a comet. After its true nature was determined, Uranus was almost named “George’s Star,” after King George III of England, but popular sentiment outside of Britain was against doing so in favor of a more traditional name derived from Greek mythology. Circled by 27 known moons and a system of rings much fainter than Saturn’s, Uranus has the distinction of having an axial tilt 98 degrees from the vertical, thus orbiting the Sun “rolling like a bowling ball” rather than “spinning like a top” the way the other planets do. Like even more distant Neptune, Uranus has been visited by only one spacecraft—NASA’s Voyager 2.
Planets Gone Loopy: If not for the Sun, Mercury would be observed to pass Saturn three times this season, first it on October 8 moving eastward, then reversing its motion and backing up, passing Saturn again on October 30, both encounters positioned low in the southwest just after sunset and unfortunately washed from view by the Sun’s glare. Resuming its normal motion, Mercury passes Saturn for a third time on November 26, when both planets have separated far enough from the Sun to be visible in the early morning sky, rising slightly more than an hour before dawn. Such a series of passes, resulting from one planet making a “retrograde loop” in the vicinity of a slower-moving, more distant planet, is referred to as a “triple conjunction.”
On October 18, a penumbral lunar eclipse occurs, not easily detectable except in photography, as the Full Moon passes through the barely-noticeable outer portion of Earth’s shadow. Centered over Western Africa, the eclipse is in progress at moonrise for U.S. locations and nearly over for the West Coast. Observers on the East Coast may notice a subtle shading across the Moon’s southern hemisphere soon after moonrise.
Do we actually stop “saving daylight” on November 3, when the U.S. returns to Standard Time? What IS “Daylight Saving Time,” anyway? Contrary to popular myth, it wasn’t invented by Benjamin Franklin, who famously said “Early to bed and early to rise makes a man healthy, wealthy, and wise,” and who invented other things like bifocals, lightning rods, the Franklin stove, and who tried to electrocute a turkey for dinner but accidentally shocked himself senseless instead (he survived, although the ultimate fate of the reprieved turkey is unknown)...but that’s a story for another time. Modern Daylight Saving Time was conceived as a 2-hour time-shift by New Zealander George Vernon Hudson in 1895. The idea was to shift clock-time so that evening activities could take place during the extra daylight hours of the summer months, and an early justification was that it supposedly saved energy by requiring less use of coal, and, eventually, electricity. The idea was independently conceived and championed in 1905 by Englishman William Willett, who observed that many people tended to sleep late during the Summer months, wasting the morning daylight, also realizing that shifting the clock allowed him to continue playing his favorite game of golf later into the evening. The idea wasn’t actually put into practice until 1916 in Germany to help alleviate coal shortages during World War I. But does shifting the clock so that more daylight hours occur at the end of the day really save energy? What might be saved at the sunlit end of the day may be used in the mornings, when people who rise during the darker morning hours would need artificial lighting, so do the two balance each other out? There are numerous other arguments supporting each side of the debate, with farmers, retailers, the entertainment industry, sporting goods manufacturers, energy commissions, and tourism bureaus weighing in, all armed with data, studies, and statistics to support them, and today, the heated controversy over whether Daylight Saving is necessary continues.
On November 3, a hybrid, or annular-total, solar eclipse occurs as the New Moon moves between Earth and the Sun, casting its shadow across the Atlantic Ocean and into Central Africa. It’s called a “hybrid” eclipse because where the Moon’s shadow first touches Earth’s surface in the Western Atlantic, our planet’s curvature causes the point of contact to be slightly farther away from the Moon, and as a result, the Moon’s ever-so-slightly smaller silhouette doesn’t quite cover the Sun’s disk. For a brief several seconds at the start (the westernmost end) of the shadow-path, the outermost edge of the Sun’s disk is visible around the Moon as an annular eclipse. As the shadow moves eastward, the curvature of Earth quickly shortens the Earth-Moon distance enough so that the Moon can completely obscure the solar disk, causing a total eclipse along the rest of the shadow-path.
Discovered a year ago, in September 2012, Comet C/2012 S1 ISON reaches perihelion on November 28, passing an astronomically-scant 680,000 miles from the Sun’s surface and thus qualifying as a “Sun-grazing” comet. This could be good...or bad: passing so close to the Sun could cause the comet to brighten significantly as its ice sublimates into a gaseous, fluorescent coma, releasing reflective particles of dust into its tail—some early and perhaps overly-optimistic prognostications suggested it could become as bright as a full Moon! However, being so close to the Sun, it would be washed from view at the same time by the Sun’s glare and not easily visible until some days afterward, when its separation from the Sun has increased. On the other hand, comets are commonly described as “dirty snowballs,” and if ISON is particularly fragile, the Sun’s gravity could pull it apart as it passes near. At any rate, the final visual brightness of a comet cannot be predicted, so we’ll just have to wait and see what the comet itself wants to do. After having been hidden in the Sun’s glare since June, the comet was recovered visually in August, but it appeared fainter than brightness forecasts said it should be. Interestingly, the comet will be closest to Earth (40 million miles) on December 26, and on January 14, Earth will pass near the inward-bound portion of the comet’s orbit, which may be littered with debris released by the comet, and some astronomers wonder if this may give birth to a new “ISONid” meteor shower.
A newly-discovered comet, C/2013 R1 Lovejoy, will be in the same part of the sky as Comet ISON in November. Although it’s not expected to reach naked-eye visibility, it was discovered photographically by Australian observer Terry Lovejoy (his fourth discovery) using a relatively-small 8-inch telescope, so it should be observable at perihelion through similar instruments, if not binoculars. This and the much-anticipated ISON will join frequent visitor Comet Encke in the predawn sky on November 9, forming a diagonal line of objects stretching from low southeast to high south, with Encke and ISON in Virgo the Maiden and Lovejoy in Cancer the Crab (ISON in the middle), topped off by Jupiter in Gemini. Comet Lovejoy will pass closest to Earth (38 million miles) on November 23 and closest to the Sun (81 million miles) on December 25.
Wait—“Comet Encke,” too? Yes! Comet 2/P Encke, discovered in 1786 but not recognized as a periodic comet until 1819, has the shortest-known period of any comet, returning to the inner solar system every 3.3 years. Despite having made as many trips through the neighborhood as it has (this being its 62nd recorded appearance), it still has enough volatiles to form a characteristic coma and tail when it nears the Sun, and though it is not expected to be a naked-eye object, it should be visible in large binoculars. Encke is thought to be the parent body of the Northern and Southern Taurid showers, two branches of a long-lasting display (the Taurid Complex) which is active from late-September through November and which is weak (5 meteors/hour) but known to produce bright fireballs (so bright in 2005 that they were dubbed the “Halloween fireballs”). Encke is also suspected by some astronomers to have been the parent body of the asteroid that exploded over Tunguska, Siberia, in 1908. The comet itself will be nearest Earth on October 17, joining with fellow comets ISON and Lovejoy in forming a parade of comets in the predawn sky in early November, and brightening just before it reaches its November 21 perihelion.