Dawn of the Space Age
On October 4, 1957, the Soviet Union launched Sputnik 1, the first artificial satellite to orbit Earth. Although its batteries lasted only three weeks, the shiny, 23-inch sphere stayed aloft for two more months. It finally fell out of orbit on January 4, 1958. Since that historic first flight, roughly 7000 satellites have been launched by more than 40 countries. Many of these have fallen out of orbit or lost power and continue to orbit uselessly while new satellites are launched to replace them, and estimates are that there are approximately 1000-1400 operational satellites currently circling the planet in orbits ranging from about 240-37,000 kilometers (150-23,000 miles) high. On almost any dark, clear night, as many as a half-dozen of these miniature, mechanical moons can be seen, silently crossing the sky in the hour or two after nightfall.
Nights of Dragon-Fire
The annual Draconid meteor shower peaks on the nights of October 7-8, radiating from the constellation Draco the Dragon. Normally a very modest display active from October 6-10, the Draconid shower has rates hardly surpassing the normal threshold of 4-6 meteors per hour. However, this year's display may have a few things going for it that give it the potential to be worth watching for. First, the peak coincides with a new Moon, so skywatchers who make the effort to get away from city lights will be able to take advantage of a dark, moonless night. Then, the Draconids are one shower whose radiant—the point in the sky from which meteors seem to radiate—is already high in the sky at nightfall. This means that meteor-watchers can start observing as soon as the sky is dark, rather than waiting until after midnight, as for most other meteor showers. Thirdly, the parent body of this shower, Comet 21P/Giacobini-Zinner (source of the shower's alternate name, Giacobinids), made its closest approach to the Sun in September, as it does every 6.6 years, replenishing the dust supply in the inner solar system. This shower has put on some good shows in the past, such as in 1933 and 1946, when it produced storm-level displays of thousands of meteors per hour, but astronomers are not predicting such a show this time around.
Draconids are described as slow-moving, apparently radiating from the "Lozenge," the roughly diamond-shaped asterism that forms the Dragon's head, but don't just look in that direction. In fact, if you look directly toward a shower's radiant, you're seeing meteors fall in short paths as they fall toward you. Instead, look off to the sides, where there's less of an the effect due to perspective, and meteor paths are longer.
Sprinkles from the Most Famous Comet of All
Even though many were disappointed by the most recent appearance of Halley's Comet in 1986, we can still enjoy a related phenomenon that is caused by the comet's dust raining through the atmosphere. The Orionid meteor shower is active October 17-26 and peaks on October 20. It's one of two showers that are caused by the iconic comet, the other being the Eta Aquarids in May. Particles of dust in the path of the comet enter Earth's atmosphere nearly head-on—as fast as 66 kilometers (41 miles) per second—making them almost as fast as Leonid meteors and usually producing about 30 meteors per hour. However, this year's Orionid peak is somewhat obscured by the light of a waxing gibbous Moon that washes fainter meteors from view and reduces the rate seen to about 10 per hour.
Seeing the Seventh Planet
On October 23, the planet Uranus is at opposition in Pisces, located opposite the Sun in the sky and rising at sunset. Typically, when an object is at opposition, it's closest to us and is as bright as it can get, as seen from Earth, although still not bright enough to be obvious in the night sky. In theory, it's barely visible to the unaided eye under perfect conditions, but it wasn't discovered until 1781, and then only with a telescope (even so, its discoverer, William Herschel, thought at first that he was looking at a comet).
Unfortunately, on the 23rd, the light of an almost full Moon—seven degrees away—is certainly bright enough to interfere with viewing. However, as one of the most distant planets from the Sun, Uranus moves very slowly and will remain against the stars of Pisces the Fishes long after the Moon has moved out of that part of the sky.
Located about halfway between the point of the characteristic "V" shape of that constellation and neighboring Aries the Ram, Uranus looks like a tiny, greenish disk rather than a pinpoint, and—like other planets—doesn't twinkle the way the stars do. Not visible because of its great distance are the faint rings of Uranus and its 27 known moons.
An Extra Hour of Night (for Most)
November 4 is when Daylight Time ends for parts of the country that observe it, and most people set their clocks back one hour ("Spring forward, Fall back") at 2:00 a.m. You could stay up late for that exciting moment (not) when official time goes from 1:59:59 a.m. back to 1:00:00 a.m., or you can adjust your clocks at bedtime on the night of the 3rd and sleep through it, enjoying the extra hour of sleep.
States that do not observe Daylight Time are Hawaii and most of Arizona (except for the Navajo Nation). Also on permanent Standard Time are U.S. island territories (Puerto Rico, Guam, and the U.S. Virgin Islands) which are near the equator, where the length of daylight doesn't vary much through the year as at higher latitudes, and adjusting clocks forward or backward during the year makes no difference.
The Leonid Meteors: Will They Roar...or Purr?
Typically, the annual Leonid meteor shower—named after the constellation Leo the Lion—produce a modest 10-15 meteors per hour. However, in 1966, they produced one of the greatest meteor storms in history, with observers estimating thousands of meteors per minute. However, such displays from this shower only happen about every 33 years, coinciding with the periodic return of the shower's parent comet, 55P/Tempel-Tuttle, the last time having been in 1999.
Active from November 6-30, the shower peaks this year on November 17th, and is accompanied by a waxing gibbous Moon. The brightness of this phase will undoubtedly wash many fainter meteors from view and reduce the number seen in urban areas to around 5-10.
Leonids are among the fastest meteors, smashing into Earth nearly head-on and entering the atmosphere at 71 kilometers (44 miles) per second. This increases the chance of seeing fireballs—or extremely bright meteors—which may become at least as bright as Venus...bright enough to overcome interference from moonlight.
Geminid Meteor Shower
The year's most reliable meteor shower, the Geminids, is active from the 4-16th, peaking on the nights of December 13-14 and usually producing about to 80 meteors per hour. The Geminid shower isn't as well known in the northern hemisphere as the Perseids of summer because it takes place when the weather is usually too cold for most people to stay outside at night. Still, this display is a good one to watch for.
While midnight is the ideal time to observe Geminid meteors, skywatchers can start looking for them earlier in the evening, since the radiant rises two hours after sunset. Even though the first quarter Moon may interfere with viewing of fainter meteors early on, it might be possible to see Earth-grazers. These are rare but beautiful fireballs produced by meteoroids skimming across the top of Earth's atmosphere, creating long, glowing trails, then returning to space. After the Moon sets around midnight, the radiant is at its highest, nearly overhead. While waiting for meteors, you can certainly appreciate the Moon and Mars close together in the sky against the stars of Aquarius the Water-Carrier.
The Brightest Comet of 2018
Most comets are extremely faint and visible only through telescopes, but on December 16, Comet 46P/Wirtanen (pronounced "WER-tuh-nen") makes its closest approach to Earth, passing 7.1 million miles (11.5 million kilometers) away. While this is 30 times the distance to the Moon and presents absolutely no risk of collision, it's still pretty close as comets are concerned, and its closest approach to Earth occurs only four days after it has made its closest approach to the Sun (perihelion), when it's most energized by our star's radiation. Despite the fact that comets are notoriously unpredictable, this comet is expected to become as bright as magnitude +3. That means it may be about as bright as the faintest star in the Big Dipper, which is easily within binocular range.
At its closest to Earth, Wirtanen will be located against the stars of the constellation Taurus the Bull, passing near the Pleiades, or "Seven Sisters," star cluster in the Bull's shoulder. Taurus is already low in the east just after sunset, giving skywatchers all night to find the comet. However, the Moon is just past first quarter on the 16th, and its phase and brightness will slowly increase from night to night until it's full on the 22nd. It passes directly through Taurus on December 19-21. Therefore, to avoid interference from moonlight, comet-hunters should try to observe during the early part of December, when the Moon is in a thin crescent phase and the comet located south of Taurus, near the border between Cetus the Sea Monster and Eridanus the River. When the Moon is out of the way and at a dimmer phase by the end of the month, the comet will have moved northward, passing Capella, the brightest star in Auriga the Charioteer, on the 23rd-24th.
The December Solstice
On December 21, Earth's axis is tilted with the north pole angled farthest away from the Sun. In the Northern Hemisphere, this is the December or Winter Solstice, when the Sun makes its lowest, shortest arc across the southern sky, and despite the fact that the daylight period now starts lengthening, it's commonly regarded by most as the beginning of winter.
At the north pole, the Sun is continuously below the horizon, resulting in 24 hours of darkness. However, the north pole has been in constant darkness since late-October and will continue to be until about mid-February. During this four-month stretch, the Sun is at least 12 degrees below the horizon, which technically defines nautical twilight, when the horizon is barely visible).
Ursid Meteors: "Bearly" Visible Under a Full Moon?
The Ursid meteor shower, active from December 17-25, peaks on the night of the 21st, delivering a modest 10-15 meteors per hour under ideal conditions, radiating from near the cup of the Little Dipper. Somewhat like the Draconids of early October, whose radiant is already in the sky just after sunset, Ursid meteors will be seen all night, although their radiant isn't as high in the sky. However, peaking this year in the light of a bright full Moon, many meteors from this shower will be washed from view.
And Just One More Time
Here's a little more information about that striking, pre-dawn celestial "conga-line" that forms in the southeast during the final ten days of the year. On December 21st, Mercury and Jupiter have their close, 1-degree conjunction just before sunrise, with Venus to their upper-right. Then, over the following mornings, the two planets slowly separate, with Jupiter climbing toward Venus while the waning Moon moves in from the west along the Zodiac, passing through Gemini the Twins, Cancer the Crab, and Leo the Lion, before finally entering the stars of Virgo the Maiden, where it passes about 6-7 degrees from that constellation's brightest star, Spica on the 30th. That's when it leads a diagonal line that rises from the horizon, followed by brilliant Venus, then slightly fainter Jupiter, and finally—the lowest on the horizon—elusive Mercury at the tail end of the line and perhaps the most difficult to see in the growing glow of dawn. This procession is also visible on the morning of the 31st, when the Moon is a bit lower and closer to Venus.
Visit an aquarium, planetarium, rainforest, and natural history museum—all under one living roof.
Download the Morrison Planetarium's 2018 Pocket Almanac to stay up-to-date on eclipses, meteor showers, satellite spottings, and more.