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The Sky This Month - September 2009

Posted in
Written by Gary Boyle, Ottawa on
Post Date: 
Thu, 2009/09/03

The Teapot’s Starry Steam

September nights are ideal for cruising the Milky Way. As the nights get progressively longer and cooler (less mosquitoes), we can now spend more quality time with the sky above. On moonless nights – the mighty planet Jupiter is the first to greet us in the south east within moments of sunset. Once you spot Jupiter, train your telescope on it. The contrasting blue sky allows viewing of subtle detail without eyestrain. Once darkness sets in and the planet brightens to magnitude -2.8, filters are required to soften the overpowering bright image.

As our western sky transforms to darker pastels of orange and blue, we eagerly scan for the first dots of white. Leading the pack is Arcturus of the constellation Bootes the Herdsman down in the west, followed by Altair from Aquila the Eagle in the south and Vega, the brightest star in Lyra the Harp overhead. Like popcorn – more and more suns reveal themselves one at a time.

Within an hour of dusk, look due south for Sagittarius the Archer that more like a Teapot. Imagine pouring a nightly cup of tea with the steam rising from the pot. This ghostly fog steadily raising all the way to Cassiopeia the Queen to the north is our home Galaxy. What you are seeing is the glow of literally millions of distant suns residing from tens to thousands of light years away.

 

 

We start this month’s list with the brightest object in Sagittarius. M8, aka the Lagoon Nebula is a superb magnitude 5.8 naked eye target. This emission nebula and is creating new stars in its ‘stellar nursery’. Taking up more area as the full moon, the Lagoon is located 5,200 light years from us. An easy way to locate M8 from light polluted skies is to move six degrees north from the orange coloured giant Alnasl – the spout of the teapot. Close to the nebula is a cluster of recently developed stars. These young one are probably a million years old.

Moving three lunar diameters north and a bit to the west we come to a dimmer object but never the less just as gorgeous – the Trifid Nebula. Catalogued as M20, it is a combination of an emission and a reflection nebula and is located 5,200 light years. Taking on the appearance of a flower’s petal, dark lanes known as Barnard 85, break up the object into three sections.

To the northern edge, we come across another stellar nursery called the Swan or Omega Nebula. Designated as the 17th entry in Messier’s list M17 is located around 6,000 light years away and 15 light year in length. Some 35 very young energetic stars light up the nebula like a flashlight.

Aside from gaseous clouds, Sagittarius is also home to a fine selection of planetary nebulae, globular and open clusters. My personal favourite globular is M22. Taking a bit more room in the eyepiece that the full moon, a low to medium power ocular will reward you with nothing short than a stellar portrait. M22 is a well-defined splash of an estimated 70,000 suns of equal magnitude. The cluster is 10,400 light years from us and thought to be 95 light years wide. It will be difficult to take your eye off this magnitude 5.1 jewel of the night.

A very odd-looking pair of objects consists of the planetary nebula NGC 6818 and the irregular galaxy NGC 6822. Separated by 41 arc minutes, these two require investigation. NGC 6818 other wise called the Little Gem Nebula will show filaments and structure especially in photography. The parent star must have died off in layers. NGC 6818 is listed at magnitude 9.2 and is around 6,000 light years from us.

NGC 6822 - Barnard’s Galaxy lies only 1.6 million lights years away and is considered as one of the closest galaxies to us. It is far from the conventional looking spiral shape with arm and a bright nucleus. NGC 6822 is an irregular galaxy glowing at magnitude 9.2. The galaxy is peppered with active HII regions of star formation.

The north east corner has a pair of galaxies We have NGC 6835 at magnitude 12.5 that is very elongated and measures 2.7 arc minutes in length. A little more than 7 arc minutes away, we come to NGC 6836, a 13th magnitude face-on galaxy that is only 1.2 arc minutes long. Before leaving Sagittarius, try looking for the now minor planet - Pluto.

If you have never been able to locate the planet Neptune, let Jupiter guide your way. Bluish green Neptune is 5 degrees east of brilliant Jupiter. However, with Jupiter’s retrograde motion to the west, the distance between the two widens to 6.3 degrees. Nevertheless, fear not. The two a full moon’s width on the night of the winter solstice.

 

 

Jupiter and more so the Jovian moons are putting on a great show. Astrophotographers are enjoying less atmospheric turbulence and the king of planets marches up the ecliptic. However, just like last month, the volcanic moon Io will cast a shadow on Europa on the nights of September 5th, 8th, 15th, 23rd and 30th visible from different parts of the continent and at different times. Check with the RASC Handbook for details.

The long awaited ring crossing of Saturn is finally upon us. On September 4th the rings will have vanished only to seen next day as sunlight begins to illuminate the opposite side. Unfortunately Saturn is very low on the horizon at sunset and dips below the horizon a mere 32 minutes after the sun has faded away. The two will be separated by only 11 degrees. The next ring crossing will be on the morning of March 23, 2025 with a separation of only 9 degrees.

The space shuttle Discovery is now docked with the International Space Station (ISS) and will be until Discovery’s scheduled landing for September 12th. You can watch the mission on your computer 24/7. The website even has a schedule of events. The ISS can be seen crossing your town or city. Find your area for predictions. Click on the date for a detailed star map.

 

Object

Type

Magnitude

Coordinates

M8

Planetary Nebula

5.8

RA:18h 03m Dec:-24d 23 m

M17

Planetary Nebula

6.0

RA:18h 20m Dec:-16d 11m

M20

Planetary Nebula

6.3

RA:18h 02m  Dec:-23d 02m

M22

Globular cluster

5.1

RA:18h 36m Dec:-23d 54m

NGC 6818

Galaxy

10.0

RA:19h 44m Dec:-14d 09m

NGC 6822

Galaxy

9.0

RA:19h 44m Dec:-14d 48m

NGC 6835

Galaxy

12.5

RA:19h 54mDec:-12d 34m

NGC 6836

Galaxy

13.0

RA:19h 54m Dec:-12d 41m

 

The full Fruit Moon is on September 4th at 12:03 EDT and the fall equinox will occur on the 22nd at 17:18 EDT. After this date, nighttime hours are longer than daytime hours.

Till next month, clear skies everyone.

Gary Boyle