JAMESTOWN, N.D. (NewsDakota.com) – Dr. Tim Bratton, Professor Emeritus of History at the University of Jamestown and Amateur Astronomer, has written a piece on observing astronomy for the month of November.
With Saturn departing from the evening sky, the other naked-eye planets are behind the Sun or rising before it as “morning stars.” Nonetheless, we do have a few predawn planetary encounters, a lunar occultation of a first-magnitude star, and some meteor showers to entertain us. The two streams of the Taurid meteor shower, which appear to originate from the constellation of Taurus the Bull, occur all through the month, but with peaks on Nov. 5 and 17. Although there are no more than five per hour, they often are pea-sized particles that create “fireballs” when they burn up in our planet’s atmosphere.
Debris from periodic comet Encke, these slowly moving meteors enter the Earth’s atmosphere at speeds of 17-18 miles per second. The Taurids are among the most brightly colored meteors; although usually yellow, they also produce orange, green, red, and blue fireballs.
Nov. 4 (Sat.): Full Moon occurs at 12:24 a.m. CDT, when it will be 51.64 degrees above the SSE horizon, 33.2 arc-minutes in apparent diameter, and 226,202 miles away. November’s Full Moon is called the “Frosty Moon” (for obvious reasons) or the “Beaver Moon,” since these aquatic rodents were actively preparing for winter at this time of year.
Nov. 5 (Sun.): Today we switch from Central Daylight Time (CDT) to Central Standard Time (CST). Remember the old saying, “Spring forward, fall back!” So before going to bed the previous Saturday night, turn all your clocks, watches, and other time-keeping devices BACK an hour, and you’ll be fine the next morning.
The waning gibbous Moon reaches perigee, its closest approach to the Earth this month, at 6:21 p.m. CST. At that time Luna will be 10.6 degrees beneath the NE horizon, 33½ arc-minutes across, and 225,039 miles distant. At 7:15 p.m. CST the 94.8% lit Moon will have risen only 3.28 degrees over Jamestown’s ENE horizon. Its left limb occulted (covered) the bright orange sun Aldebaran (Alpha Tauri, magnitude 0.85) just minutes before. Using optical aid, you might be able to see the star emerging to the upper right of the Moon’s dark western rim at 8:02 p.m. By that time the Moon will have climbed 10.58 degrees above the same horizon. Aldebaran marks the fiery “eye” of the V-shaped constellation of the Bull. In March 1794 some English astronomers (who ought to have known better) mistook a grazing occultation of Aldebaran by the Moon for a lunar “volcanic eruption” as the star winked in and out of view while passing between the mountains on the lunar limb. The sordid tale may be found in the November issue of Sky & Telescope, pages 30-33.
Nov. 10 (Fri.): Last Quarter Moon takes place at 2:37 p.m., but it will be 7.88 degrees beneath the WNW-NW skyline at that moment. Moving away from the Earth, its distance has increased to 233,075 miles.
Nov. 17 (Fri.): The annual Leonid meteor shower should attain its modest peak both this morning and Saturday morning also. The parent body of the shower, Comet Tempel-Tuttle, swept within 33,464,090 miles of Earth on January 17, 1998. This comet completes its elliptical orbit every 33 2/9 years; it reached perihelion (its closest distance to the Sun during its latest passage) on February 28, 1998, when it came within 90,782,870 miles of the star just inside the Earth’s orbit. However, much cometary debris precedes and follows it, leading occasionally to spectacular outbursts when the Earth passes directly through a dense swarm of such material. While moonlight should not be a problem this time, the Leonids have been declining over the last fifteen years, and there may be no more than 15 of them per hour. The last sizeable outbreak occurred in 2002; we’ll have to wait until 2031 or later to see if the comet’s return injects new material along its orbital path.
The Leonids are the fastest “shooting stars,” entering the Earth’s atmosphere nearly head-on at 44 1/9 miles per second; none ever has struck the Earth, as these fragile objects (most are fluffy particles no larger than a grain of sand) vaporize completely while still 54.7 to 79½ miles high. Many Leonids are bright, sometimes exploding into white, green, red, or blue fireballs; 50 to 70 percent leave vapor trails behind that can last up to 5 minutes.
If you’re a meteor fanatic, you can start observing as soon as the radiant (apparent point of origin of the shower) rises shortly before midnight; some meteors might streak directly upwards as their source rises along the NE-ENE skyline. By 5 a.m. the radiant will lie directly above yellow Algieba (Gamma Leonis, magnitude 1.99), the second brightest sun in the “head” or “Sickle” of Leo the Lion; that star will be then 33 degrees above Jamestown’s eastern horizon. Although the meteors appear to come from the radiant, they will streak away from it in all directions. Find a dark location free from artificial lighting, which otherwise hides the fainter “shooting stars”; be sure to wear warm clothing!
Nov. 18 (Sat.): New Moon happens at 5:43 a.m., when it will be 17.54 degrees below the eastern horizon, 29½ arc-minutes in apparent span, and 249,853 miles from Earth. As it will be passing then 4.54 degrees north of the Sun, no kind of solar eclipse is possible this month.
Nov. 21 (Tues.): The Moon attains apogee, its farthest distance from the Earth this month, at 12:53 p.m. At that instant it will be 11 degrees over our city’s SE horizon, a slender crescent just 9.7% lighted, and 252,358 miles away.
Nov. 26 (Sun.): First Quarter Moon transpires at 11:04 a.m., when it will be 24.64 degrees under our ENE-E skyline, 244,560 miles distant (it’s heading back toward Earth again), and 30.1 arc-minutes across.
Perhaps this November is not as astronomically exciting as others, but we should be thankful for North Dakota’s crystal clear skies! Look at http://www.spaceweather.com for daily notifications about auroras. Even though the Sun is heading toward a solar minimum of activity, it has surprised astronomers this autumn as openings in the star’s magnetic field have allowed the solar wind to interact with Earth’s upper atmosphere. Several of these aurorae have been visible low on the northern horizon in our state.
