Imagine you are standing in a fog so dense that you cannot see any objects around you. There is fog, and nothing else. You know there is a landscape surrounding you--trees, buildings, a lake, perhaps. But none of it can be seen. You take a few hesitant steps, hoping to glimpse a familiar landmark. Then, suddenly the outline of something appears before you. It is very indistinct. Nothing definite can be perceived, just the hint of something. For an instant it becomes slightly less mysterious, but then the fog enshrouds it again and it is gone. This little game continues for a few moments, until you are almost sure that what you are seeing is a building or a village, but you cannot be 100 % certain....
Old Amersham, Buckinghamshire, England
Author's photo.
Author's photo.
And now imagine it is a dark and very clear night. The humidity is low, there are no lights nearby, and you are away from any cities and towns. In the eyepiece of your 12" reflecting telescope you are seeking a galaxy of magnitude 15, at the very limit of what you are able to see on the best of nights. The sky background in your eyepiece view is black, though a few very faint stars are sprinkled across it. You have been searching for several minutes, with no luck. Suddenly, out of the corner of your eye, there is a slight flaring. Is it a faint star, near the limit of visibility? No, it's larger than a star. A moment later and it is seen again, this time as a nearly undetectable oval haze that increases in brightness when you do not stare right at it. It is probably the galaxy, but you cannot be 100% certain. You try a different eyepiece, likely a higher magnification. If it is the galaxy, it should appear again....
http://www.asod.info/?p=1920
Both cases, the foggy scene and the very faint galaxy, are extreme. Seldom is it so foggy that nothing can be seen nearby, but it does happen. And out of all the galaxies that I hunt in the darkest skies, only a very small percentage of them are at the limit of what I can expect to see. Yet just as the foggiest day seems to have more poetry in it than most average days, sometimes recognizing these really faint, difficult galaxies can be the biggest thrill of a whole night's observing.
Galaxies, being what they are, are often the most studied and most photographed objects in the deep sky (deep sky being beyond the moon and the planets in our solar system). There is no such thing as a typical galaxy, though they all have things in common. Plenty of stars, for one. However, from the largest earth-based telescopes used for observing with the human eye, even the brightest and closest northern hemisphere galaxies all look like haze. Without photography we would still not know what these island universes are, nor have seen their immense beauty. In fact, it wasn't until 1925 that the debate was settled, when Edwin Hubble, using photographs taken with the 100" Hook Telescope, was able to distinguish variable stars in another galaxy and compute their distance from earth. Since the stars were hundreds of thousands of light years beyond our galaxy, then other galaxies like ours had to exist. All of that haze we had been seeing were stars; billions of stars. We now know that there are more galaxies out there then there are stars in our Milky Way galaxy! If that isn't mathematical poetry, then I don't know what is.
Galaxies are grouped by scientists into classes, depending on their shape and their light output. The many different types need not overly concern us in this discussion, but they are important when observing. Some galaxies that do not fit neatly into any class are referred to as peculiar. More poetry! For me, the galaxies that provide the most poetry when observed are called "edge-on." That is, we are seeing them along their equatorial line. They appear long and thin, with a central bulge. Though only haze to the eye, to the imaginative mind we are seeing billions of stars shining together to produce a grayish haze coming from hundreds of millions of miles away. The bulge is the center of the galaxy, always its busiest, most populated and most active place. As an extra bonus, some of these edge on galaxies have dust lanes, material within the galaxy that has not yet been converted into stars. Our own galaxy is filled with such dust, as are many other galaxies.
An edge-on galaxy, photographed through a large telescope. Note the central bulge
and the very distinct dust lane running the length of the galaxy.
http://mgio.arizona.edu/older-mgio-journal-entries
In the eyepiece, sometimes only the central bulge of such galaxies can be seen. However, other galaxies clearly display their full length, and these can send shivers up one's spine when viewed. With fainter galaxies the full length sometimes comes through only like our foggy day analogy--a glimpse now and then of the full extent of the object. Patience, and looking indirectly at them (called averted vision) often show faint objects more readily than staring at them. More poetry!
A second type of galaxy that telescope observers love to view is called "face on." Now we are situated above the galaxy, looking directly down at it (or it is "above" us--it's all relative in deep space). With some of the brighter and closer galaxies, we can see the haze shaping itself into spirals, called arms. Sometimes, these arms show tiny clumps of brighter areas. These are not commonly seen in smaller amateur scopes, but they are star forming regions, places where stars are either being born or are newly born. Realizing that one is actually looking at star birth in another galaxy can be an overwhelming experience. Galaxies where such regions can be viewed in larger amateur instruments are not hard to track down.
Nice comparison of a sketch from the eyepiece
and a photograph. This is Messier 101, a face-on
spiral galaxy, displaying arms and bright knots,
which are actual star-forming regions.
http://www.perezmedia.net/beltofvenus/archives/001416.html
Galaxies abound in the skies of Summer, Autumn and Winter. However, the best time to see them is Spring. At this time of year, we are in the part of our orbit around the Sun when our night sky faces away from our own galaxy. The Milky Way, with all of its stars and dust, can make it difficult to see beyond, into really deep space. But when we look up at the sky in Spring, it can seem a barren field to the naked eye. There are fewer stars, no Milky Way; just plenty of dark space. We are looking directly opposite the center of our galaxy, our view now extending out into deepest intergalactic space. This part of the sky is simply swimming in galaxies; bright ones, faint ones, large ones and small ones, and everything in between. They are often so crowded together that more than one of them can be seen at a time in the eyepiece. Sometimes they are physically close to one another, and even interacting, but just as often they happen to be in a line of sight, from our vantage point. A closer galaxy may appear larger and brighter, with a further and fainter one seemingly right beside it.
It is a wonderful experience to see and contemplate one galaxy on a fine night, but to see two, three, four or more all at once can really test the limits of one's ability to comprehend. Just what are we really seeing? How many stars? How many possible planets? It is beyond mind boggling. These experiences are relatively common for amateur astronomers, though I never find anything common about them. It is always such a thrill and a privilege that sometimes after such an experience I simply stop observing for the night! Such treats are thus best reserved for the end of an observing session, rather than at the beginning.
Several galaxies can be viewed at once sometimes.
http://cseligman.com/text/atlas/ngc7436wide.jpg
Just as intensely foggy days can reteach us the essence of what is, so can observing faint galaxies through a telescope. By stretching our imagination we can fill in some of the details that the eye cannot fully grasp. By combining what we know and what we can imagine, there is a meeting of science and poetry; between the universe and humankind. It is so true that we and our planet are insignificant when compared to objects that are on a cosmic scale, such as galaxies. However, this fact in itself is significant. And poetic.
Clear skies.
Mapman Mike
