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The Sky This Month - July 2013

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Written by Gary Boyle on
Post Date: 
Mon, 2013/07/01

Our Home Galaxy


Summer is the time of year to enjoy the great outdoors whether it’s camping, fishing or gazing at the starry sky on a clear night. Sitting outside in the dark and looking up has been the past time of humans for thousands of years. No matter if you are eight or eighty; something magical occurs when we simply stare at those tiny points of lights high above our heads. At times our eyes follow a slow moving satellite as it traverses the night sky until we lose it in the earth’s shadow. More exciting and sometimes startling moments occur with a bright, fast moving meteor as it cuts the dark of the night and in some cases, light the ground. And let us not forget the subtle and fluid motions of the northern lights that can take over the entire night with poise and beauty as we stare and click our cameras in amazement. The Sun has been spewing material lately and it should be a matter of time till your see and photograph one.



However, with the few examples I just set out, none is more intriguing than viewing Milky Way in all its glory.  The beauty of astronomy unfolds as we cast our eyes on the mysterious greyish band stretching from the famous W of Cassiopeia the Queen in the north, to the main nucleus of Sagittarius the Archer in the south. Like looking at a dusty piece of furniture edge on, we see the collective glow of millions of distant suns that make up the various arms of our spiral galaxy. In fact our solar system resides on the inner portion of the Orion arm. The Milky Way galaxy measures about 120,000 light year in length and 1,000 light years thick except for the central nucleus that balloons out to 16,000 light years. It holds an estimated 200,000,000,000 stars. And yet our little island of suns is only one of about the same number of galaxies in the known Universe.


Taking on the iconic shape of a gigantic tea pot, the constellation of Sagittarius and its surrounding area plays host to no less than 15 Messier objects which can easily be seen in a pair of binoculars. You will of course need a telescope to magnify these targets. The largest and easiest object to find is the mammoth open cluster of M7. Located close to the stinger in Scorpius the Scorpion, M7 can be enjoyed in simple binoculars. At first glance you will count about 30 stars but many more are seen in a telescope. As you can see by the chart, not too many galaxies are for the choosing and they are of the 14th to 15th magnitude range.


To locate a total of seven Messier objects fairly easily, first position your scope on the star Alnasl - the very tip of the teapot’s spout. Now start heading up till you come across our first treasure referred as M8. Known as the Lagoon Nebula and a favourite at public star parties, M8 is a stellar nursery located 4,100 light years from us is where molecular clouds of hydrogen are slowly condensing. Over millions of years of this condensing and squeezing to high pressures and temperatures, a star is produced. At visual magnitude 5.6, this emission nebula is an easy naked eye target as seen from a dark location. Moving up a tad we come across M20 or the Trifid Nebula. Residing a bit further at 5,200 light years, we see the combination of the tell-tale red emission nebula producing even more stars and its bluish reflection nebula in which star light is bouncing off it light a flashlight on fog.



Keep moving up north, stopping at other open star clusters till you come across the Swan Nebula of M17. This is yet another star forming region around 6,00 light years away. As you march north and cross the border into Serpens, your eyes will pick up the Eagle Nebula. Here we have the famous M16 thanks to the Hubble Space Telescope’s lovely portrait of the “Pillars of Creation”. Again the Eagle is a star forming region that sets about 7,000 light years from us. It just misses naked eye visibility but at magnitude 6.4 is an easy target in binos or a telescope finder. M16 is positioned in the arm next to us or Sagittarius arm.


One of the best globular cluster I have ever seen is M22. This must see object of found a few degree east of Kaus Borealis which is the top star of the teapot. At just over 10,000 light years from us, M22 is one of the closest of its kind. It measures some 97 light years in width and of its estimated 70,000 stars, astronomer have identified thirteen variables. M22 is a big, beautiful globular that appears a bit larger than the full moon. Astronomers have found two black holes lurking within this cluster. Be sure to include this gem on your next observing run.


The planet Venus is marching up the western horizon and can now be seen for an hour and a half after sunset. If skies are clear on the 3rd, train your scope on the planet as it is immersed in the Beehive cluster. This could be a nice photo shoot but remember they are low in the sky. Keep following Venus as it leaves Cancer and moves through Leo. On the 22nd Venus will be 1.2 degrees north of Regulus, making them a striking pair. Saturn is the other planetary showpiece of the night. The ringed planet is now in the second half of the sky and sets after midnight at the beginning of the month.


The planet Jupiter is now making an early morning appearance in the east and will be south of the open cluster M35 on the 5th and then Mars has a closer encounter with the cluster on the 16th. On the 21st Mars is 0.8 degrees north of Jupiter. This month’s new moon (lunation 1120) occurs on the July 8th at 07:14 UT with the first Ramadan starting on the 9th and locating the very thin 3% lit moon will be a challenge. As a guide, the thin crescent will be almost eleven degrees south of Venus and a bit to the west. The Full Thunder Moon washes out the sky on the 22nd at 18:16 UT.    


Until next month, clear skies everyone.


Gary Boyle