The Winter Sky - Part I

Whether you are a well-seasoned observer or new to the field of astronomy, the winter sky is a treasure to view. Step outdoors the next clear night and feast your eyes upon eighteen brilliant Suns covering a span of six constellations. They are Taurus, Auriga, Gemini, Canis Minor, and Canis Major. Let us start the show with our team leader – Orion the Hunter. This famous figure seen from both hemispheres is by far the most recognized pattern in the entire sky. Two bright stars signify his shoulders, two more for the feet along with three stars lined up marking his belt. We can even the outline of his trusty sword hang down from his belt. Located in the sword is the most beautiful object in the heavens, M42, the Great Orion Nebula. This emission nebula consisting of mainly hydrogen gas is slowly producing new stars. It is located 1,500 light-years from Earth with its shell of hot gas measures some 42 light-years across. Keep in mind one light-year equals close to ten trillion kilometres.

Mythology states our great hunter armed with shield and club is battling Taurus the Bull to the upper right. The brightest star Aldebaran (the eye of the Bull) located 60 light-years away is a giant red star in its latter stages of life. Its brightness is pegged at magnitude at its brightest while measuring 40 times larger and shining 350 times brighter than our Sun. If we replaced our Sun with Aldebaran, it would appear as large as a basketball at arm’s length. Aldebaran marks a wide-open star cluster called the Hyades some 150 light-years from us. Aldebaran is not a true member of the cluster but appears in the line of sight. The Hyades cluster consisting of about 100 members, resides 90 light-years behind the bull’s eye.

We next come across the bull’s heart known as M45 (The Pleiades) located to the right and listed three times farther than the Hyades, which is a wonderful example of a three-dimensional effect. Common referred to as the Seven Sisters, this open cluster consisting of a few hundred stars. Counting all seven Suns with the naked eye is a good test for overall sky transparency. Each month of 2006, the Moon swings close to M45 allowing a great photographic opportunity. The Moon will dive under the cluster on February 6th at 8 hours Universal Time. 


Winter Constellations & Highlights


Comet hunter Charles Messier’s first catalogue object (M1) is the ghostly remains of a star that is blown to pieces during a supernova explosion close to one thousand years ago. Commonly known as the Crab Nebula, it is around 6,300 light-years from us. The explosion was seen in 1054 AD by the Chinese and was visually seen daylight for 23 days. It is suggested that the energy of 400 million Suns was released during the event. 

A couple of other smaller objects are NGC1817 and 1807 which form a very sparse cluster double with each holding a dozen or fewer Suns. They glow at magnitudes 7.7 and 7.0 respectively. While in the area, be sure to check out the orangey coloured planet Mars to the right of the Pleiades cluster. As the days tick by, the Earth-Mars distance widens as our neighbouring world gets progressively dimmer.

Moving above our Hunter is Auriga (The Charioteer). Alpha Aurigae - the brightest star is called Capella – the She Goat star. This very close double star measures 42 light-years from us. Its separation is about the closeness of the Sun and Venus. No less than nine open clusters occupy Auriga’s boundaries including three wonderful Messier objects. All three are found in the southern portion of the constellation and semi-lined up. Our first stop is M38. A wide cluster measuring about three quarters the size of the Moon. Lying close to 4,100 light-years away, it’s stellar neighbourhood measures 20 to 25 light-years wide and holds 60 or so stars. M38 glows at magnitude 7.7. Moving on to the lower left we come across M36, roughly the same distance as M38. Hosting about 70 stars in a tighter, 17 light-year area – its brightness is magnitude 6.3. Continuing on our course we meet our but not least jewel, M37. A gorgeous collection of more than 150 Suns sparkling at magnitude 6.2. Estimated distance is 4,400 light-years this busy community is some 22 light-years wide. This cluster is superb at about 80X and even a treat in binoculars. We will examine the remaining three constellations next month.

The two planetary jewels of the night are visible. The Lord of the Rings – Saturn is at opposition is visible all night long. Any telescope will reveal its ring system measures a mere one kilometre in thickness and consists mostly of ice particles from the size of a snowflake to that of a house. The entire system spans 282,000 kilometres in width or about three-quarters the distance to our Moon. Saturn is presently about 1.3 billion kilometres from Earth The Cassini spacecraft is now in orbit, examining the ringed planet as well as its many Moons. Discoveries are being revealed daily.

We end out the night with the king of planets, mighty Jupiter. This is the first object Galileo Galilee aimed at his new scope on the night of January 7, 1610. A moderate six-inch mirrored scope can detect a few of Jupiter cloud bands along with up to four Gallian moons. More on this planet next time

Until next month – clear skies everyone.

Gary Boyle

eNews date: 
Wednesday, February 1, 2006