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Health & Fitness

Look Through My Eyepiece

Come with me for a night of observing under April's sky!

Although you may have assumed that I am a constant watcher of the night sky, the truth has been sadly different for the past many months.  Finally, last Wednesday night (April 17th) I was able to get the telescope out on an exceptionally clear night, with no snow on the front lawn, and no need to wake up early the next morning.  Let me take you on a journey through my eyepiece.

I was truly shocked to discover, after setting up the scope and turning on the onboard computer, that my last observing session was on December 6th.  I’ve lost an entire season of viewing!  I intentionally planned to merely observe visually Wednesday night – no photography, just using my aging, but well-trained eyes – to run through a list of objects.  Photography involves a level of setup that is inevitably complex and brings with it a bit of stress – I was looking for relaxation instead, and I was not disappointed.

With the moon nearly at first quarter, and therefore right overhead at sunset, this was an easy first target.  My timing could not have been better – after having observed the Moon hundreds of times in my lifetime, I was delighted to see a feature I had never actually seen before – the Purbach Cross. 

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This is a pattern caused by lighting effects along the rims of two craters (Purbach and Werner) at the terminator of the Moon – the line separating the illuminated half from the shadowed half.  On lunar phases leading up to the Full Moon,
this is the sunrise horizon on the lunar surface.  The Purbach Cross is a very distinctive bright X observed against a black background, and is at its best visibility for about 90 minutes in each lunar cycle.

The Moon through any pair of binoculars or telescope is a fascinating sight, and I took the opportunity to survey both some familiar features and some that I had never noticed before.  The Moon seldom looks the same twice, due to slight variations in lighting and the exact time of the lunar day in which an observation is made.  This night I was struck by a horseshoe-looking pattern that seemed to be formed by three mountain ranges and some medium-sized flat bottomed craters.  Nearby was a very small crater with a rille (lunar valley) running through it. 

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After consulting a digital atlas of the Moon, I’ve identified the area I was seeing –
the small crater is Hyginus, 6 miles in diameter (marked with a red dot in the
attached image), and the horseshoe pattern was to the northeast, with the top
of the horseshoe pointing southwest, but this is not readily visible in the atlas, as you can see in the snapshot I've included.

Farther north, I easily spotted the massive Alpine Valley, a gash 79 miles long and 7 miles wide running through the lunar Alps along the northeastern rim of Mare Imbrium.  Directly east of this valley I was fascinated by a flat floored crater with an apparent diamond shape, which is the crater Egede. The shape is most likely truly circular, but because it is far north on the Moon, foreshortening makes it appear elliptical, and lighting suggested the corners.

Leaving the Moon, I next felt compelled to visit our three clusters in Auriga, which were the topic of the last post.  M36, M37 and M38 did not disappoint, but I didn’t dally long on these.

I next chose to observe a set of multiple star systems.  These are similar to "binary stars” in which two stars orbit one another, but in multiple star systems there is a larger family of objects involved – some of these may be in the same star system, others may just appear in the same direction in the sky but be light years in front of or behind the main star system. 

What makes binary stars of interest is the closeness of the pair, and it can be a visual challenge to see them as separate stars.  On this night I had already noticed that the “seeing” – our astronomer’s term for the steadiness of the atmosphere – was quite poor – features on the Moon seemed to be beneath a boiling pot of water.  This limits the ability to observe binaries, but I was up for the game anyway.

My first target was the star system Zeta Cancri (the naming convention is to list the stars of a constellation using the Greek alphabet in roughly their order of brightness – Zeta Cancri is therefore a quite dim star in the constellation Cancer).  This system consists of 5 or possibly 6 very tightly packed stars, commonly observed as a simple pair (as in my case last night). The stars are all similar in size to our Sun, located about 83 light years away. One of the stars may actually be a pair of red dwarves.

Although my telescope is capable of separating one of these into its two components, the seeing did not allow this on Wednesday night. Four additional stars lie in the same field of view through the telescope, and were easily seen, but these are much dimmer and more distant stars not in the Zeta Cancri system.

Next up, the beautiful binary star 90 Leo.  This is a tighter pair than the two main members of Zeta Cancri, and I was pleased to see them as separate stars on a rather poorly stable night.  This pair is much more distant, at around 2000 light years, and the brighter of the pair is a very young star (a B spectral class, for those who read my earlier “She Comes In Colors” post.

Ok, the binary star game can go on all night – there are literally thousands of doubles in the sky on any given night, and truth be told, after seeing a few it becomes less than exciting to see more in one sitting.  So I moved on to nebulae next.

I didn’t mention that I took a peek at Jupiter right after leaving the Moon – it was down in the trees to the East, and the view was actually terrible, but Jupiter is always worth a peek.  My first nebula of the night was NGC 3242, better known as “the Ghost of Jupiter”. 

I’ve always enjoyed this object. It is the same apparent size as Jupiter through the telescope, but is about 1500 times dimmer (hence the name). Not a planet at all, the Ghost is the remains of an exploded star – a shell of gas expanding away from a central white dwarf star, which causes the gas to glow a pale blue.

The other nebula of the evening was the Eskimo Nebula (aka the Clown Nebula, or NGC 2392).  This was a tough target Wednesday night because of its close proximity to the Moon, whose light washed out the background sky.  But I pulled out a little-used nebula filter, which blocks most light and lets through only the pale blue light of this form of nebula, and I was able to get a rather good look into this object. Similar to the Ghost, the Eskimo is a stellar remnant with a central white dwarf, but this object has a bit more structure – a brighter central core and dimmer outer shell.

After the nebulae, I went for some easier targets, before proceeding to the night’s main mission…

I observed two spectacular open star clusters.  In an open cluster, each star of the group can be observed individually.  I chose M48 in the constellation Hydra as the first target.  This is a gorgeous collection of about 100 or so stars, filling the field of view of my telescope, shining a brilliant blue white.  Located 1500 light years away, it fills a ball of space 23 light years in diameter.

The second open cluster I picked was M67, a very dense cluster in the constellation Cancer.  This is one of the oldest known open clusters in our Milky Way galaxy.  Typically open clusters separate over a few 100 million years, pulled apart by gravitational forces as they rotate about the center of the galaxy.  M67 has stars aged upwards of 4-5 billion years, including a large number of red giants, and allows astronomers an excellent opportunity to study the evolution of a group of stars known to be of nearly the same age. The view in the telescope was majestic, with a variety of colored stars somewhat evenly spaced through the central portion of the eyepiece view.

But these were just the preliminary observations of the night.  The true objects of a quest on a night in April, with the Moon in a less than quarter phase, are GALAXIES.  This is a time of year when the Earth is pointed away from the galactic plane during the early evening in the northern hemisphere, and we peer out into intergalactic space.  In the constellations of Leo, Coma Berenices and Virgo, as well as in neighboring constellations, we find nearly 100 galaxies within the “reach” of a telescope that an amateur might own.  (For the professional,  there are 10’s of thousands to choose from, if not more).

Observing galaxies through any telescope on the East Coast is definitely an acquired skill, and the observer must approach this quest with the understanding that to see the objects at all is an amazing achievement. To expect the telescope to reveal their true beauty, as captured by the Hubble Space Telescope, for example, is unfortunately unrealistic given our lighting conditions.  But this fact has never bothered me, for to simply be able to see light created millions of years before our Man existed – for these galaxies are located from 10 to 100 million light years distant – is enough of a miracle for my satisfaction.

I started with one of the brightest galaxies visible on April evenings, the Whirlpool Galaxy, M51, in Canes Venatici.  This is a galaxy with two cores,  connected by an extension of the spiral arm of the main core.  Each core contains billions of stars, and the bridging arm several billion more.  This
night I was able to clearly see the two cores, and after staring over a minute with averted vision, I was able to barely discern the connecting bridge, as well as a general extended haziness that marked the arms of the major core.  It is  astounding to realize that despite the 100’s of billions of stars shining from that direction in space, we can at best see the galaxy as a subtle grey haze due to the nearly unfathomable distance.

Having verified that the night was reasonable for galaxy hunting, I proceeded through my list of targets.  M63, the “Sunflower Galaxy”, has about the same brightness, apparent size, and approximate distance (37 million light years) as the Whirlpool.  Most galaxies are structured as flat plates with bulging centers – rather like a classical “flying saucer”.  The angle that the plate makes with our vantage point from Earth will make the galaxy appear more or less elliptical. 

While the Whirlpool Galaxy appears face-on, and therefore roughly circular, the Sunflower Galaxy shows as a definite ellipse with a bright center and fading edges.

M64, the “Blackeye Galaxy” came next.  This galaxy is also elliptical in aspect, and has a dark lane of opaque gas running through its center, though on this night I was able only to see the general elliptical shape and no dark lane.

M88, a more distant galaxy at 60 million light years, shows as a much smaller ellipse, which actually aids in viewing by making the light more concentrated and in better contrast to the surrounding grey sky.  This was followed by the more appealing M104, a galaxy seen edge-on, with a distinct dark line through its heart created by the galaxy’s edge.  Both the lenticular shape and the dark line were quite apparent after staring for a good minute or two.

Three additional galaxies – M49, a rather circular blob, and M53 and M54, appearing next to each other in the sky and within the same field of view of the telescope – wound up my night of exploration.  Though there were dozens more galaxies that I could have observed, including many old favorites, by this time I was growing tired, so I packed up the observing equipment and called it a night.

If you are wishing you were able to experience these observations in person, you may consider enrolling in my Introduction to Astronomy course for children ages 8 and up. Full details of this course can be found at www.turnerclasses.com.  Our next session starts in August, and I would love to have you join us!

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