What's Up in the Night Sky

September 2015 - Vol. 19, 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, Denab (Cygnus) and Altair (Aquila). Scorpius and the bright star Antares occupy the southern sky. . Look for another famous asterism, “the teapot” (Sagittarius). 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. The September 2015 issue of the contains the final installment of the constellation of the Summer Triangle.

MERCURY will be in the evening sky for the first part of the month, best observed from the southern hemisphere. VENUS will reach greatest brilliancy on the 21st shining brightly in the morning sky. MARS is still rising in the morning sky and will approach Regulus for a conjunction on the 24th. JUPITER reappears in mid-month, rising with the constellation of Leo. SATURN is in the constellation of Libra and sets in the early evening approaching conjunction in November. URANUS rises mid-evening and will be occulted by the Moon for some observers at the far South, see details below.

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. Unfortunately some of these events may occur during daylight hours in your area.

DATE	EVENT
01	Neptune at opposition. Uranus 1 deg N. of Moon, occultation from Antarctica, S. South America, Falklands.
04	Mercury greatest elongtion E. (27 deg)
05	Aldebaran 0.5 deg S. of the Moon occultation from Eastern North America, Western Russia, Alaska, and northwestern Asia.
10	Venus 3 deg S. of Moon. Mars .5 deg N. of Moon.
11	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 here. This phenomenon will be visible until about October 10th as long as the Moon does not interfere.
13	A partial Solar Eclipse in the southern hemisphere centered over the Indian Ocean may be visible from the tip of Africa, the southern half of Madagascar and parts of Antarctica.
15	Mercury 5 deg S. of Moon.
14	Moon at apogee.
19	Saturn 3 deg S. of Moon.
21	Venus at greatest extent illumination at mag -4.8, blasting the pre-dawn sky.
23	Equinox, the Sun rises due East and sets due West, also provides an equal day and night outside of equatorial regions.
24	Mars .8 deg N. of Regulus.
28	Moon at perigee, large tides may be expected. Total Lunar Eclipse will be visible from Western Europe, Eastern North America, all of South America and Greenland. Totality will last 72 minutes and the Moon at perigee will appear larger than it did during the April 4 3clipse earlier this year. The surface of the Moon is expected to appear darker in the north and observers may detect changes in the appearence of the disk during totality.
29	Uranus 1 deg N. of Moon, occultation from parts of Antarctica, South Africa, tip of Madagascar.
30	Mercury at Inferior Conjunction.

Lunar Almanac for September 2015

Phases of the Moon	Phase and Date(s)	Best viewed before local midnight
	New 13	Deep Space Objects
	1st. Qtr 21	Planets & Moon
	Full 28	Moon
	Last Qtr 05	Deep Space & Planets

Topic of the month: The Summer Triangle, Cygnus

The Summer Triangle is an asterism, a group of stars that are not a constellation, but have earned a popular nickname. It is formed of three bright stars that dominant the summer sky, Vega, Deneb, and Altair. Each of these stars is the brightest member of its constellation, thy are Lyra, Cygnus, and Aquila respectively. This year, What's Up in Night Sky will pay tribute to the three constellations that are part of the Summer Triangle. This month features Cygnus, home of the well known blue giant, Deneb.

lyra Deneb is the brightest star of the constellation Cygnus, the swan, a high flying bird that dominates the night sky and the summer Milky Way. Deneb is a blue giant that is among the 20 brightest stars in the night sky Deneb is designated Alpha Cygni. The constellation is so far north that it spends a lot of time in the northern sky, visible all year round from northern locations. (Although it may not be visible all night.) If you have trouble seeing a bird, you may resonate with Cygnus's other identify, the constellation is often called the Northern Cross. If you watch the cross all night from the northern hemisphere, you will notice that it twists in the sky, so that by the time it sets, it appears to hang upright over the western horizon. It is rather fascinating that the cross takes this position in the inky evening sky on December 25 right after sunset.

Another star in the constellation is Beta Cygni, known as Albireo. Albireo is a beautiful double star, in a small telescope the stars appear bright yellow and blue. The pair may also be split with binoculars. The central star of the Northern Cross is the second-magnitude star, Sadr, interesting to view in a small telescope. The star fields of the Milky Way between Albireo and Sadr are magnificent. Notable galactic clusters in Cygnus include M29, M39, NGC 6819 and NGC 6866.

The Milky Way in the constellation of Cygnus offers much in the way of bright and dark nebulae, for it is here that the "Great Rift" of the Milky Way begins. This rift is the same dark lane that we can observe in distant spiral galaxies, for the dark material of the rift absorbs light from the stars. It is composed of gas that some day may form new stars in our galaxy. For deep sky observers, Cygnus offers one of the finest supernova remnants known as the Veil Nebula. The star that formed this magnificent nebula exploded over 5,000 years ago, it's spreading debris field now covers over 3 degrees of the sky for Earth based observers. This expanding wreath of gas has two separate designations, NGC 6960 and NGC 6992. The western portion of the veil (NGC 6960) is located near the star 52 Cygni while the eastern portion displays fabulous filamentary structure. For bright nebulae, Cygnus offers NGC 7000, the North American Nebula approximately 3 degrees E of Deneb. So called for it's resemblance to the continent, this bright field may be noted with the naked eye at a dark site. It is often seen in binoculars and a small telescope will reveal its brightest jewels.

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

The star chart above was generated by Stellarium, a free open source planetarium program. This image was created by Dawn Jenkins, using Stellarium and a graphic editing program to format the image for this web page. Stellarium offers much to amateur astronomers and is being used in planetariums. 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.