Night_skies_08-30

Jeff Green | Jul 31, 2008

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Many of the summer visitors currently seen in our area greatly appreciate its dark skies – relatively unpolluted by smog and glaring lights – when compared with most cities, and they find the local setting ideal for exploring the richness of the Summer Milky Way, whether with binoculars or the unaided eye. Share with them some of its wonders on any late evening this month, whenever the weather allows, and begin the tour by pointing out the distinctive “W” of the constellation Cassiopeia clearly seen in the northeastern sky. From this star-pattern, which to our ancestors showed the figure of a great queen, the Milky Way sweeps almost overhead and includes the great bird Cygnus The Swan, sometimes also called The Northern Cross, from its outline of stars, and then it flows southward into the southern sky where the Milky Way is at its widest and densest and where the distinctive shape of the Teapot of Sagittarius is easily evident with the handle to the left and spout to the right. As you guide your guests along this pathway of a myriad stars, remember that it is not just a collection of so many points of light – each one a sun like our own enormous sun, but it is an arm of our home galaxy, The Milky Way Galaxy, containing a total of over 200 billion suns! Also, during August we have a chance, even with the unaided eye, on a moonless night under unpolluted skies, to look BEYOND our own galaxy and to see the famous Andromeda Galaxy, which is one other whole galaxy, also composed of hundreds of billions of stars, and part of a group of over 20 such galaxies forming what is called The Local Group. This “close neighbour” of the Milky Way Galaxy is only (!) about 2 million light-years away. (Remember that a light-year is the distance light travels in A YEAR, and it travels a million kilometres in about 3 seconds!!) To find the Andromeda Galaxy, begin with the right side of the “W” of Cassiopeia, after 11:00 p.m. on any clear moonless night, and trace a line downward and to the right toward the eastern horizon. About half way along that line, you should see a faint “finger print” on the sky. That is it! Remember to tell your guests that what they are seeing there is actually thousands of times farther away than anything else visible in the sky, and that it is a whole galaxy, larger than our own, in fact, and the light from its stars has taken over 2 million years to reach our eyes.

Among the five bright planets that may be seen with the unaided eye, only one will probably be seen by every reader this month. Whether the other four are seen will depend on circumstances – both local conditions and attention to detail in planning to observe at the right time. Jupiter continues, as it did last month, to dominate the southern sky throughout the night. It may be seen in the southeastern sky shortly after sunset, and it sets in the southwest shortly before dawn. There is no mistaking the brilliance of this, the largest planet in our solar system, as it appears this month to the left of The Handle of “The Teapot” – which is how modern astronomers describe the stars of the constellation Sagittarius. Those who observe Jupiter with good binoculars or a small telescope will be able to see the four largest of its moons circling the planet and changing position from night to night. This month the other four planets all appear low in the western sky for a period of time after sunset. Seeing them at all will demand a clear view of the western sky right down to the horizon, a view UNOBSTRUCTED by trees and buildings! Reddish Mars may be seen due West from about hour to 1 hour after sunset, and when first seen, will likely be up above the horizon by a little more than the width of a fist held at arm’s length. Binoculars will aid in seeing it. The other three planets, that is, Mercury, Venus, and Saturn, appear to the right of Mars, also in the time between hour and 1 hour after sunset. For those fortunate enough to see them, they perform a wonderful “dance of the planets”. In the first week of the month, Mercury will not be seen, but Saturn and Venus will be visible to the right of Mars. Be prepared for a challenging but extremely interesting sight, if you have clear skies and a perfect western horizon on August 2nd, 3rd, and 4th when a thin crescent moon will appear respectively just to the left of Venus, Saturn, and Mars!! That’s hour after sunset EACH of those 3 evenings!! Mercury joins the group after August 10th, and it appears to the right of Venus. On August 12th and 13th Venus appears extremely close to Saturn, and after that, it appears to the left of Saturn. Mercury appears to move closer to Venus each evening until by the 20th they are very close, and after that it is seen to the left of Venus. In the last 10 days of the month, with brilliant Venus so close, it should be easy to identify the planet Mercury which many people have never seen or identified with certainty. I have great memories of the after-sunset “dance of the planets”in May 2002; this time it will be more challenging since they are lower in the western sky, but again it will probably be well worth the effort of finding a place with a good view.

With the Perseid Meteor Shower reaching its peak in mid-August, we can expect to see many bright “shooting stars”– as meteors are incorrectly called – during the nights from August 9th to 14th, with the maximum activity expected after midnight (especially from 2:00 a.m. to 5:00 a.m.) on the night of August 11-12. (Fortunately, local moonset that night is at about 1:20 a.m..) For the peak hours, I would advise finding a place away from any form of light pollution, relaxing on a reclining lawn chair (with blanket and insect repellent), and observing for several hours looking to the eastern or northern part of the sky, though these meteors may appear in any part of the sky. Record the numbers of meteors seen per hour. I would be interested in hearing results.

Though this month brings us to another “eclipse season”, neither one of its two eclipses is visible from any part of central Canada. At New Moon, a total solar eclipse is visible from Canada’s High Arctic and parts of China on August 1st, and at Full Moon, a partial lunar eclipse is visible from Africa, Europe, and Asia on August 16/17.

More information about observing the spring and summer sky is available in the book entitled “The Beginner’s Observing Guide” which is now available at Sharbot Lake Pharmacy.