Groups of Stars

Star clusters are amongst the easiest celestial objects to locate and observe. Opposed to some planetary and diffuse nebulae that are faint, clusters are wonderful groups or balls of stars that show nicely in binoculars. One of the best areas to begin your search is along the glorious band of the Milky Way Galaxy. Starting in the most southern portion we begin with M7. Known as Ptolemy’s Cluster, it contains about 80 suns and appears larger than twice the size of the full moon. Even at 980 light-years away this cluster is huge. One summer I observed its reflection off a very calm lake. It was a perfect mirror image.

Over the course of the past few months, I have pointed out one or two globular clusters associated with a particular constellation. However, as the months tick by, we come to that time of year where these starry blobs containing tens of thousands to hundreds of thousands of stars are seen in greater numbers. One reason why summertime is best for viewing globular clusters is they tend to populate in most part, around the heart of our galaxy, near the nucleus.

Like snapping a photo of mosquitoes around a streetlight, our Milky Way Galaxy is home to 158 known globulars. The most spectacular cluster located in the northern hemisphere is M13. Located some 25,000 light-years from us in the constellation Hercules, M13 glows at magnitude 5.8 and can be glimpsed on a clear moonless night from a dark observing site. Astronomers have estimated this supercluster to contain more that one million stars within its width of 145 light-years. Small scopes or binoculars will show a patch of grey without much resolution, whereas medium to large instruments will show a greater definition of individual stars, even to the center. Words cannot portray the view of M13 in big scopes.

If you can pull yourself away from this fabulous object, move a full moon’s width to the east till you come across a magnitude 11.6 galaxy catalogued NGC 6207. Located 46 million light-years from the earth, it sets a very nice contrast with M13 when both fit in a low power eyepiece. Now here comes a real challenge. If your aperture is large enough and you are blessed with good seeing conditions, try to locate IC 4617. Nestled between M13 and NGC 6207, is a tiny, faint and extremely far galaxy. It is around 15th magnitude but lies at a staggering half a billion ly from us. In all my years of observing, this is the farthest galaxy I have seen.

Another lovely globular cluster in Hercules is M92. Two-thirds the size of its neighbour nine and a half degrees away, but still is a must-see object. M92 holds a lesser population of about 300,000 suns and is a little slender at 109 light-years wide. Astronomers have discovered 16 variable stars within its boundaries. A superb transparent night is needed to spot this magnitude 6.5 fuzz without optical aid and is a good test to the night’s seeing. It lies about a thousand light-years farther than M13. If you are up to another challenge of faint galaxies, there are a few 14th magnitude candidates to the north such as NGC’s 6327, 6329 and 6332. To its west, we have IC 4645 and UGC 10759 and south of M92 are NGC 6344 and MCG 7-35-56.

The only planetary nebula belonging to Hercules is NGC 6210, located in the lower portion of the main asterism. NGC 6210 is located some 10,000 light-years away and takes on the appearance of a turtle. It has a decent brightness of magnitude 8.9 but at only .2 arc minutes in width, it could be a challenge to see detail.

Moving down one constellation, Ophiuchus owns no less than ten globular clusters. he brightest and prettiest being M10 and M12, both of which are listed as magnitude 6.6 and very resolved. These are located 13,000 and 18,000 light-years respectively. Resting on the Ophiuchus – Scorpius border is another magnitude 6.6 gem called M62 and is a bit farther at 22,000 light-years. Measuring 4.3 arc minutes, calculations predict that it is some 43 light-years in width.

Shifting your telescope to Sagittarius, we find another dozen or so faint fuzzies scattered across the region. Of all these objects in Sagittarius, my personal favourite is M22, found 2.5 degrees east of the orange giant star named Kaus Borealis - the tip of the teapot. This K type sun lies 77 light-years from earth. M22 is set amongst the Milky Way stars and is a little more than 10,000 light-years from Earth. With an angular diameter of the full moon, any eyepiece of a telescope will show a lovely display of evenly bright stars. I can watch this one all night long. Although globular clusters tend to look alike, they are quite different. Each has its own unique structure.

Our premiere planet of the solar system is rising in Sagittarius in the southeast just after sunset. Jupiter reaches opposition on July 9th and will shine all night at magnitude -2.9. This is the closest our worlds will be as it orbits the sun and a good chance to see detail in its cloud tops. Although moving slowly up the ecliptic in its 11.86-year journey around the Sun, Jupiter is still low and we must deal with a lot of atmosphere and turbulence. I have found that hot, hazy, humid nights are best for planetary observing when the atmosphere is calm and the hazy darkens the planet a bit. As always, numerous transits occur across the Jovian surface and as the months move on, some double and the odd conjunction is bound to occur.

We alas say goodbye to Saturn and Mars as they try to break through evening twilight. As July opens, watch Mars scoot past Regulus on Canada Day while racing to Saturn to form nice conjunction on the10th, when the two will be fit nicely in a low power eyepiece. On July 5th, the Regulus Mars and Saturn line up for a Kodak moment with the thin crescent Moon. So circle the calendar and get your cameras ready. Now that Venus is slowly moving from behind the Sun, you should be able to pick it up within an hour after sunset low in the West North West in July’s second week. Once you have found it – follow its steady climb over the weeks and months.

We are also at that time of year when you can hunt down the outer planets, namely Uranus, Neptune and Pluto. We start off with poor little Pluto that got demoted last year to minor planet status. Use the link to the chart and try your luck hunting it down. Once you think you have spotted it, sketch or photograph the area and check back in a few nights to see if something moved. As for the other two gas giants, they rise a bit later in the night. Neptune is nestled in Capricorn and Uranus is in Aquarius. They are easy telescopic targets, appearing as bluish-green fuzz balls. In fact, Uranus can be picked up with the naked eye if you know where to search.

Only one meteor shower slated for the last few days of July. The South Delta Aquarids will peak on the 27th with a dismal 5 to 10 meteors can be seen between 1 a.m. and 4 a.m. Well, at least the moon will be in the waning crescent phase.

Comet Boattini that gained naked eye visibility during May and June is now low in morning skies slicing through Eridanus, Taurus and Cetus between 7th and 8th magnitude and fading.

And now that summer is firmly here, numerous star parties are being held throughout North America. Here is a calendar for your area. If you have never attended a star party, try to plan at least one. It is an excellent opportunity to enjoy dark skies and learn more about the celestial landscape above. If you are thinking of buying a telescope or accessories, some parties or astro weekends could have swap tables. But looking through the wide range of instruments in the field and speaking with the owner can help you decide on the right telescope.

Until next month clear skies everyone.

Gary Boyle

eNews date: 
Saturday, July 1, 2017