Cygnus the Swan
July 2002 :
Until I sat down to write this column, I wasn't really sure what my topic for July was going to be! Jupiter and Saturn would be finally lost in the solar glare. Brilliant Venus would be brightening and beckoning for anyone to look at her, but I did a column about the Goddess of Love within the last year.
July has a couple of meteor showers during the last week of the month, but unfortunately the Full Moon is on the 24th, thereby washing out all but the brightest shooting stars. That has never deterred me from observing them myself, or suggesting you do the same. But the Perseids are coming up in August and they usually put on a much better show (and this year moonlight will not be a limiting factor).
What about a constellation I haven't written about in recent years? Ah, yes! One of my favorites that lies among the stars of the Milky Way...Cygnus the Swan will be perfect for July!!
What do you see when you look up into the night sky? If you live well away from major light pollution sources you can perhaps see several hundred stars on a good night. There may even be enough stars visible for you to connect the stars with imaginary lines to form patterns in the sky. Though you can make up your own star patterns, sort of like a Rorschach ink-blot test, today s star patterns are quite old. One of these constellations, Cygnus the Swan (also known as the Northern Cross), can be found in one of the richest star regions in the sky.
Thee, silver Swan, who silent, can overpass?
A hundred with seven radiant stars compose.
The graceful form: amid the lucid stream
Of the fair Milky Way.
--Eudosia
During July after sunset, Cygnus can be found about halfway up the northeastern horizon, immersed in the myriad of stars that comprise the Milky Way, That gossamer cloud of tenuous light stretches through Cygnus to the heart of our galaxy in Sagittarius. You ll probably pick out the pattern of a cross before you see a swan in these stars. Here s how both patterns are represented.
Deneb, the northernmost and brightest star of the constellation, forms the top of the cross, or the tail of the swan. The center star of the cross, called Sadr, also represents the hen s breast. The easternmost star that forms the cross is called Gienah, meaning the wing. The westernmost star of the cross, has no proper name, but it represents the right wing of the swan. In astronomical nomenclature this star is Delta Cygni, the fourth brightest star in Cygnus. Head down the Milky Way from Sadr and you ll come to Alberio at the base of the cross. Alberio means "beak," and represents the beak of our swan.
We’ve now outlined this celestial bird in the heavens, and one can easily imagine the Swan flying over the river of stars that comprise the Milky Way. This constellation is more important to Christians who see it as a cross, because during December, just before Christmas, the Northern Cross sits upright on the north-western horizon for northern hemisphere viewers.
The mythology of Cygnus is not quite as exciting as that of other constellations. Though all the myths try to describe how the star pattern ended up in the sky, none represents this pattern of stars any better than a story told by Ovid. When Phaeton, son of Helios, was thrown into the river Eridanus after his unfortunate journey across the sky in his father s sun chariot, his relative Cygnus deeply lamented the death of this brave young man. After Phaeton had disappeared beneath the river, Cygnus frequently plunged into the stream to seek him. The gods were so incensed (as they always seemed to be) that they changed him into a swan. Which is why today the swan pensively paddles about the water, frequently thrusting its head beneath the surface. This myth covers it all -- the swan and the Milky Way analogy, as well as the behavior of the swan.
Is there anything of interest to observe within the confines of Cygnus? Yes indeed! Just with your naked eye in a dark sky you will have no difficulty seeing the cloud-like Milky Way stretching through Cygnus. In the middle of this celestial bird the Milky Way divides into two separate streams of stars. Take a look with binoculars to start with and scan this area. It is a very beautiful region of space. If you have a telescope of any size, don’t hesitate to train it on this area of sky. Agnes Clerke, a late 19th- and early 20th-century astronomy writer described Cygnus as perhaps the most lovely effect of colour in the heavens. Indeed, there are more red and orange colored stars in this region of space than anywhere else in the sky. Scan around with a telescope and you’ll see what I mean. The red stars are most striking. You will be well rewarded for your search efforts.
Go back to the top of the cross, Deneb (the tail of the Swan), and scan with binoculars a little northeast of this star. If you have a dark sky and your binoculars provide a wide view (7 X 50 s are good for this task), you may glimpse the North American Nebula, so called because this area of dust and gas resembles North America as it would appear on a map. A dark sky is an absolute necessity to locate this wonderful object.
Use binoculars to locate a large open cluster of stars north of Deneb. It s called M39 and contains about 20 bright stars. A low-power eyepiece on a small telescope will allow the object to fill the entire field of view.
Just south from Sadr one can find another open cluster called M29. This one only contains about eight bright stars, but the cluster is more compact than M39. The four brightest stars of this group form a square. The cluster can be found using binoculars, but a low-power telescope will enhance the view.
And then there s one of the finest double stars in the sky right there in Cygnus. It s our old friend Alberio, the beak of the Swan or the bottom end of the Northern Cross. When double star observing was somewhat new, every observer tried to outdo one another when describing the colors of the double stars they were observing. For instance, the components of Alberio were described as topaz yellow and sapphire blue. Well, I call them the Cub Scout stars, blue and gold. The scouts who visit us at Seagrave Observatory certainly like that description.
Another more difficult double star to observe is Delta Cygni. Try to resolve the star into two components using a six-inch telescope. The faint companion is bluish.
In a really dark sky using a large telescope, or with a smaller telescope using a O-III nebula filter, you might be able to pick out the Veil Nebula. The remnants of a supernova explosion long ago, the Veil can be found off Gienah. With a nebula filter and a dark sky you should be able to spot it fairly easily. Without a filter you’ll need a lot of patience plus some incredible sky conditions. The filter enhances the emission spectra of the nebula, making it easier to detect.
So get out there and give Cygnus a thorough examination. Whether you use your eyes, binoculars or a telescope, the Swan has much to offer. The accompanying star map will give you an approximate idea of where the objects I discussed in the article can be found. Unlike the Swan who often keeps its head below the surface of the water, all you have to is keep your eyes to the skies.
