September 2011

Your guide to the stars

You can use the chart as a guide when looking at the night sky. The chart shows the sky as it will be at 10:30 p.m. on Sep. 1; 9:30 p.m. on Sep. 15; and 8:30 p.m. on Sep. 30.

Hold the chart so the direction you are facing is at the bottom. For example, if you are facing north, turn the chart around so the “N” representing north is at the bottom as you hold it out in front of you. The center of the chart represents the portion of the sky you see if you look straight up.

To keep your eyes adjusted to the darkness as you look a the night sky, use a red-light flashlight to view the chart. You can make your own by putting red cellophane over the light or by coloring the lens of the flashlight with a red marker pen.

Sun: Sep. 1 – Sunrise: 7:04 a.m.; Sunset: 7:52 p.m. / Sep. 15 – Sunrise: 7:13 a.m.; Sunset: 7:34 p.m. / Sep. 30 – Sunrise: 7:22 a.m.; Sunset: 7:15 p.m. (exact for Waco, TX)

Moon: Sep. 4: 1st Quarter / Sep. 12: Full / Sep. 20: 3rd Quarter / Sep. 27: New

Night Sky Events

Held at arm’s length, the width of your fist is 10º and the width of your index finger is 1º . The width of a full Moon is ½º .

September

Note: September is a good month to see the zodiacal light in the morning.

4 Sun. evening: The Moon is at 1st quarter.

12 Mon.: The full Moon is called the Harvest Moon, Fruit Moon, and Corn Moon.

16 Fri. morning: Bright Jupiter is to the left of the much brighter waning gibbous Moon in the west southwest, and the next morning is below the Moon.

20 Tue. morning: The Moon is at 3rd quarter.

23 Fri. morning: Mars is to the upper left of the crescent Moon low in the east.

23 Fri.: Autumn equinox – the beginning of fall in the Northern Hemisphere when night and day are of approximately equal length.

27 Tue.: The Moon is new.

Naked-eye Planets

The Sun, Moon and planets rise in the east and set in the west due to Earth’s west-to-east rotation on its axis.

Evenings: Saturn (early evening, setting in west), Jupiter (late evening, rising in east)

Mornings: Mars, Jupiter (east), Mercury (early in month)

* Mercury is low in the east early in the month.

* Venus is still hidden the glare of glare of the Sun.

* Mars is up in the east well before sunrise.

* Jupiter rises in the late evening and is high in the south by morning.

* Saturn, very low in the west in the early evening at the beginning of the month, is all but lost in the Sun’s glare by month’s end.

Constellation of the Month

Cygnus as depicted in Urania's Mirror, a set of constellation cards published in London c.1825.

Cygnus has one bright 1st-magnitude star, Deneb, which represents the swan’s tail. Its head (actually beak) is a fainter but special star named Albireo. Those two plus three other central stars form an informal pattern (called an asterism) known as the Northern Cross with Deneb at the top and Albireo at the bottom.

Deneb also combines with the brightest stars of two other constellations, Vega (in Lyra the Lyre) and Altair (in Aquila the Eagle), to form the large Milky Way Triangle (also known as the Summer Triangle), currently seen high overhead.

There are several myths related to Cygnus dating back at least to the Greeks. In the most commonly told story, Zeus (Jupiter), the king of the gods, had the hots for the beautiful but human Leda., wife of a local king. (It made no matter to Zeus that both were married as he had the hots for many women – mortal and immortal – and fathered more children than Genghis Khan.) To seduce Leda, he disguised himself as a handsome swan; among their demigod (half-god, half-human) offspring were Helen of Troy and the Gemini twins, Pollux and Castor.

In my favorite story, a minor Greek god named Cygnus and the mortal Phaeton were close friends who liked to compete with each other as young lads often do. Once they decided to race through the sky to the Sun and back. Unfortunately, they rounded the Sun too closely and their chariots were burned, causing both to fall back to Earth. When Cygnus regained consciousness, he set out to find his buddy. Sadly, he found that the dead body of Phaeton was entangled in roots at the bottom of the River Eridanus. When he tried to retrieve his friend’s body for burial, he was unable to dive deep enough, and while grieving on the river’s bank, called out for help from Zeus. The king of the gods offered to turn him into a swan whereby he could dive deeply enough to reach Phaeton’s body – but it would come at a price: he would have to give up his immortality and remain a moral swan until he died. Cygnus agreed to the terms, recovered his friend’s body, and gave him a proper burial so his spirit could move on to the afterlife. When Cygnus eventually died, Zeus placed him in the night sky to honor him for his unselfish loyalty to his friend.

Star of the Month

Albireo from Wikimedia Commons

Albireo, the star representing Cygnus the Swan’s head or beak, is more than meets the eye. Located 380 light-years away, to naked eyes and even through most binoculars, Albireo is an ordinary-looking 3rd-magnitude star, fainter even than the stars forming the Big Dipper. But seen through a telescope, even at low power, it will knock your socks off. It is a breathtaking double star – a bright golden yellow star with a fainter pastel blue companion – considered by many, including myself, to be the most beautiful of all double stars. The two stars may be a binary star system, bound gravitationally and orbiting each other, but if so they are widely separated and take 75,000 years to complete one orbit.

Astro Milestone. Sept. 23, 1846, astronomers Johann Galle & Heimrich d’Arrest discovered the planet Neptune from Germany’s Berlin Observatory. Their discovery was made based on the predictions and position-calculations of Urbain Jean Joseph Leverrier of France.

Star Parties

The Central Texas Astronomical Society’s simultaneous free monthly star parties are Sat., Sep. 17, at the Lake Waco Wetlands, Belton’s Overlook Park on Stillhouse Hollow, and Hubbard City Lakes Park beginning at 7:30 p.m. CTAS also owns and operates the Meyer Observatory at the Turner Research Station near Clifton, TX; the next monthly observatory open house is Sat., Sep. 10, from 7-9 p.m. See www.centexastronomy.org for more information.

Paul Derrick is an amateur astronomer who lives in Waco. His website (www.stargazerpaul.com) contains an archive of past Stargazer columns, a schedule of his upcoming programs, star parties and classes, and other basic stargazing information. Contact him at: paulderrickwaco@aol.com, or 254-723-6346, or 918 N. 30th St., Waco, TX 76707.