What's Up in the Night Sky

July 2015 - Vol. 19, No. 7

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 will be in the morning sky for the first half of the month. This apparition once again favors observers in the southern hemisphere. VENUS in the evening sky, continues to remain close to the giant planet, JUPITER, in conjunction on the 1st and again on the 31st. Keep watching this month as these two bright planets dance with each other in the evening sky. Our sister planet will also encounter the crescent moon this month, before plunging into the sunlit sky in mid-August. MARS is not visible this month and will reappear in the morning sky in August. SATURN is visible in the constellation of Libra. URANUS rises around midnight this month.

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	Venus .4 deg S of Jupiter
05	Moon at perigee.
06	Pluto at opposition. Earth at aphelion.
09	Uranus 0.8 deg N. of Moon, occultation from Antarctica, Indian Ocean, western Australia.
10	Venus greatest illumination.
12	Aldebaran, Alpha Tauri 0.9 deg S. of the Moon occultation for northern Japan, eastern Russia, Alaska, Canada, Greenland, and Iceland.
18	Jupiter 4 deg N. of Moon.
20	Venus .4 deg N. of Moon occultation for New Guinea, N. Australia, and French Polynesia.
21	Moon at apogee.
23	Mercury in superior conjunction
24	Mercury greatest elongation W.
26	Saturn 2 deg S. of Moon.
28	S. Delta Aquarid meteor shower, expect 20 meteors per hour at peak.
30	Venus 6 deg S. of Jupiter.

Lunar Almanac for July 2015

Phases of the Moon	Phase and Date(s)	Best viewed before local midnight
	New 16	Deep Space Objects
	1st. Qtr 24	Planets & Moon
	Full 02 & 31	Moon
	Last Qtr 08	Deep Space & Planets

Topic of the month: The Summer Triangle, Aquila

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 Aquila, home of the well known bright star, Altair.
lyra
Altair is the easternmost star of the Summer Triangle asterism, from a northern latitude it is the last star to rise and the earliest to set. Altair is a first magnitude star, flanked on either side by stars beta (Alshain) and gamma (Tarazed) Aquilae. At 3.7 mag, Alshain is actually fainter than Tarazed at 2.7 mag. The distance between these three stars is about 5 degrees, a measurement that has been used as a "cosmic yardstick" by amateur observers. Altair is one of the closest stars to our own Sun, a mere 16-light years away. Another interesting star in the constellation is Eta Aquilae, a variable star of the Cepheid type. It fluctuates from 3.5 mag to 4.4 mag every 7 days, and the fluctuations are very easy to detect, especially by comparing its brightness to the nearby Alshain, Beta Aquilae. Another star to note is R Aquilae, a Mira-type variable, that varies by 6 levels of magnitude from 5.5 to 12. Its period is approximately 270 days, shorter than the 300 days period that it had when its variable nature was first identified in 1856.

Aquila is also home to many deep sky objects, including several planetary nebulae (NGC 6741, NGC 6751, NGC 6781, and NGC 6803 to name the brightest.) A good amateur telescope will be needed to resolve details on any of these. Aquila is also located near the Great Rift of the Milky Way and includes some prominent dark nebulae including B133 and B 143. A good open star cluster, NGC 6709, contains about 40 stars. The constellation even contains an 11-mag Globular star cluster, NGC 6760, and a distant galaxy, NGC 6814, that shines at 12.2. It is worth mentioning that the star Lambda Aquilae is very near the famous Wild duck cluster, a fabulous open cluster in the Scutum star cloud. Also designated M-11, this cluster is best seen in binoculars, but can be seen with the naked eye from a very dark site. The cluster is composed of thousands of stars, and is actually located in the nearby constellation of Scutum.

--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.