What's Up in the Night Sky

September 2016 - Vol. 20, No. 9

This Month's Night Sky - NOTE: The next paragraph describes the sky as it appears at 10 pm EST (11 pm EDT) near mid- month. The sky also looks this way at 11 pm EST (midnight EDT) during the beginning of the month and at 9 pm EST (10 pm EDT) by month's end.

Bright blue-white Vega (Lyra) shines high overhead as it "leads" the Summer Triangle across the night sky. The "Triangle" is the summer’s most prominent asterism and is made up of three stars: Vega, the brightest, Deneb (Cygnus) and Altair (Aquila). In the SW, Arcturus (Bootes) is dropping towards the horizon as Spica (Virgo) vanishes from sight below. Also look for Antares (Scorpius) low in the SW. The stars of constellations Scorpius and Sagittarius, embedded in the "Milky Way" (part of one of the spiral “arms” of our galaxy), are at their best this month. Look for another famous asterism, "the teapot" (Sagittarius). The "Great Square of Pegasus" asterism, now appears on the E horizon just before the onset of morning twilight. These are the stars of autumn that will take over when the northern summer wanes!

MERCURY is well placed for the evening twilight sky early this month, an apparition that favors observers in the southern hemisphere. The planet moves from the evening sky to the morning sky Sep 20-30, this will be the best morning apparition for northbound observers. VENUS continues shining in the evening sky. MARS sets in the evening, in the constellation Ophiuchus. JUPITER sets in the evening sky, diappears as the planet approaches conjunction with the Sun. SATURN sets in the late evening. URANUS in Pisces, nearing opposition on October 15. The outer planet NEPTUNE in the constellation of Aquarius will be visible all night for telescopic observations.

Review how to determine Angular Measurement.

Calendar of Events

NOTE: For those observers not in the ET zone, convert the calendar times to your zone's time by subtracting one hour for CT, two for MT and three for PT. Don't forget to adjust for Daylight Savings Time when necessary by subtracting one hour from your planisphere's time. Dawn and dusk times must also be corrected. See your local newspaper, TV news, or cable TV's Weather Channel for sunrise and sunset times or check with the U.S. Naval observatory. Unfortunately some of these events may occur during daylight hours in your area.

DATE	EVENT
01	Annular solar eclipse crosses Africa and Mozambique.
02	Neptune at opposition. Jupiter .4 deg S. of Moon, occultation from Eastern Russia, southwest USA, Central America, northern South America, Caribbean.
03	Venus 1.1 deg S. of Moon occulation from central Russia, northern Mongolia.
10	Moon at apogee.
16	Mercury in inferior conjuntion.
15	Neptune 1.2 deg S. of the Moon, occultation observable from Europe, western Russia.
18	Moon at perigee.
21	Aldebaran 0.2 deg S. of the Moon occultation from eastern Africa, Middle East, center and parts of South Asia.
22	Equinox. Don't try standing an egg on end, it won't work! Sun sets due East and due West for the northern hemisphere.
26	Jupiter in conjuction with the Sun.
27	Regulus 1.7 deg N. of Moon.
29	The Zodiacal Light or "false dawn" is visible in the E about 2 hours before sunrise. This pyramidal glow is caused by meteoroids, dust particles spawned by passing comets, etc., that have settled into the ecliptic plane (path followed by the Sun, Moon and planets), reflecting the Sun’s light before it rises. This phenomenon will be visible for the next two weeks.

Lunar Almanac for September 2016

Phases of the Moon	Phase and Date(s)	Best viewed before local midnight
	New 01	Deep Space Objects
	1st. Qtr 09	Planets & Moon
	Full 16	Moon
	Last Qtr 23	Deep Space & Planets

Topic of the month: Scorpius

This season the constellation of Scorpius is playing host to 2 naked eye planets, Mars and Saturn, and so it seems fitting that this month's almanac features the stars of the scorpion. The stars of this constellation were long thought to represent the earthly scorpion, a deadly creature that carries a poisonous stinger on its tail. Some astronomers used the scales of the constellation Libra to represent the claws of the scorpion. This will make all of the constellation on the ecliptic animals, thereby creating a zodiac or "circle of animals.", the stars in Libra are actually called the north and south claw. This scorpion in mythology was sent to sting Orion, these two constellation are mortal enemies and never appear together in the sky. Scorpius must set before Orion can rise! In the Chinese culture, this area of the sky has been identified as a dragon, part of the "Azure Dragon of the East.

Classical constellation of Scorpius with the claws from the constellation of Libra

The brightest star of Scorpius is the red giant, Antares, a star that could be a subject of the monthly topic all by itself. One of only two red giant first magnitude stars (Betelgeuse is the other) its apparent magnitude is .96 almost 1. It is a class M0.5 supergiant. Antares is so red its name means, "rival of Mars" or anti-ares. The star was also called "Cor Scorpionis" or heart of the Scorpion by the Romans. This star is also a double star, its greenish companion is only visible in telescopes larger than 6 inches when the separation favors Earth observers. There are many other well-known stars in the constellation, Beta Scorpii is a notable double star, easily separated by a small telescope. Lambda Scorpii, called Shaula, is on the list of the 50 brightest stars in the sky. Its name means "the Sting" This part of the constellation is very low on the horizon for northern observers. The entire constellation of Scorpius appears overhead in the southern hemisphere, providing a great view of some of the finest objects in the summer, er, winter sky. Shaula is a variable star with a period of about five hours, the star varies 1.59 to 1.65 so its variable nature will not be readily evident to the naked eye.

Since the constellation is near to the center of the galaxy, their are many star clusters. Two beautiful clusters, M-6 and M-7 are of the open variety. These are fine binocular objects, but they also look great in a wide field lens of a small telescope. There are also several globulars in the constellation, notably M-4, that may be the closest globular to Earth. M-4 has a bar-like structure that may be noted in small telescopes. It is an old cluster, containing many white dwarf stars. Also notable is M-80, another fine globular. There are many other objects in Scorpius, including dark nebulae. One notable star cluster is NGC-6231 that may have been cataloged by Messier if the constellation was higher in the northern sky. This cluster is surrounded with bright nebulosity that may remind one of the Pleiades. This article features only a few of a large treasury of stars, clusters, and nebulosity in the Scorpius region of the sky. This summer the constellation has been the focus of many star parties due to the presence of Mars and Saturn.

--See You Under the Stars!
Astra for Astra's Almanac

The star chart above was generated by Stellarium, a free open source planetarium program. The above image was created by Dawn Jenkins, using Stellarium and a graphic editing program to format the image for this web page. Editing was done for educational purposes only. Stellarium offers much more to amateur astronomers and is being used in planetariums and to guide telescopes in the field. Simple charts like the one above can be used on the internet for non-profit, illustration purposes. Proper credit is due of course! Thank you to the makers of this fine program from Astra's Star Gate.