Some Light Science Reading. The Constellations: Draco

As first appeared in the May 2012 edition of the Syracuse Astronomical Society newsletter The Astronomical Chronicle.


Image generated with Starry Night Pro 6.

We return to our circumpolar constellation discussion begun with the Jan/Feb/March 2012 issue (our first “quarterly” report) by scaling up the Northern Horizon towards Draco the Dragon.

Draco, like all reptiles, is a bit on the dim side. Most of its constituent stars are in the 3 to 4.5 Magnitude range, making it an easy target in dark skies but a bit of a hunt near larger cities. If you’ve never looked for it before, it rivals Ursa Minor (the Little Dipper) in terms of “meh” apparent brightness in the sky (so it is far less pronounced than the Big Dipper or Cassiopeia, the two most prominent Constellations in this part of the sky).

Your best bet for identifying the stars in Draco may be to start right at the head and work your way down (and around, then over, then up, then way over the other way). One of my recent discoveries is that the head of Draco is, itself, a noted asterism (or noteworthy arrangement of stars that are not of the proper 88 Constellations) referred to as “The Lozenge” (“1” in the image above). I had been subconsciously thinking of Monty Python references to throw into this article and realized that saying “The Lozenge” several in a low John Cleese voice a la “The Larch” just about does it. The head of Draco is made from the brightest stars in the Constellation and does make for a reasonably easy target, as it sits between the two bright stars of the Little Dipper’s bowl (“2” In the image at right) and Vega (“3”), the ridiculously bright star making its triumphant return to Spring skies (if you’re at Darling Hill near sunset, you will see Vega as one of the first stars to appear above the Eastern Horizon well before it gets really dark). For those of you familiar with the Keystone (another famed asterism) that makes up the torso of Hercules (“4” in the image above), simply drive your eyes to the left-ish during the early night.

The historical origins of Draco as a lizard of any kind are localized to the Mediterranean, and these origins go back far enough that Draco is one of the Almagest’s Original 48. The Greeks, and so the Romans, saw Draco as a Dragon (or, at least, lizard) of generally ill repute. Draco was seen by the Greeks as a guard of Hesperides’ golden apples and/or a guard (or target, depending on how you read the sentence) of Jason’s mythical golden fleece. The Romans saw Draco as the remains of the dragon killed by their goddess Minerva. It is perhaps fitting that, if you imagine Ursa Minor (the Little Dipper) as an ax on a questionably straight handle, then Draco is precariously on the celestial chopping block preparing to be cleft in twain.

The body of Draco is a healthy mix of single and double stars. In the boring single star category are Giausar, Thuban, and Nodus I. The double star list includes Edasich, Aldhibain, Altais, Rastaban (“eh mahn!”), Eltanin, and Grumium.

Thuban is one star in Draco to spend a bit of time on. In fact, it’s one to spend several thousand years on. As late as 2700 B.C.E., Thuban held the place of Polaris as our North Star. The Earth may seem reasonably unchanging with respect to the seemingly unchanging arrangement of stars of our 100-year-ish lifetimes, but on the geological or cosmological timescales our Earth is as dynamic and fast-moving as that famed clay dreidel. The 26,000-year cycle we know as the precession of the equinoxes (shown above) is one of those processes that requires nearly the entire history of what we know as civilization to mark significant timespans for, but it is reported in several places that Thuban was of significance to the Egyptians in their building of the pyramids over 5 millennia ago (I would be happy to report that Thuban was the North Star that the main shaft of the great pyramid of Cheops was aligned to, but I’ve found conflicting reports online from otherwise reputable locations, so will simply report that the Egyptians very likely knew that this star appeared to move far less over the course of the night than any other and, therefore, held it with great regard).

For those observing at Darling Hill or anywhere south of Syracuse, Draco is a tough reptile to sustain one’s astronomical appetite on. At least two comets are currently passing through Draco at the moment. One, LINEAR (C/2011 F1), is just off the Spindle Galaxy M102 (we’ll come back to that) and, at 3 a.u. and closing, may improve beyond its apparent magnitude of 12.5. Draco also hosts Garradd (C/2008 P1) far beyond its tail star. At an apparent magnitude of 21.30, you have absolutely NO chance of seeing this comet from Darling Hill.

Draco is regrettably light on deep sky objects as well. The local color (at about 3400 light year) is provided by NGC 6543, known as the Cat’s Eye Nebula (above). This is regarded as one of the most structurally complex nebulae in the Night Sky, although this complexity is only revealed through astrophotographic studies. NGC 5866 (below), also known as the Spindle Galaxy (which is very likely Messier 102, although some debate exists), is one of the great photographic sights in astronomy to my eyes. This edge-on galaxy view produces amazing density of material and spindly, fibrous clouds of dust and stars along the plane of the galaxy and a bright glow of stars all around this dense, dark line.

Now, the long curving body of Draco and its positions near the North Star does afford it one benefit in the Northern Horizon. Satellites! There are many bright (brighter than magnitude 4.0) satellites that follow paths over the Earth’s poles, meaning those Constellations near the North and South poles are constantly getting pierced by manmade weather, communications, and “other” satellites. Simply letting my copy of Starry Night Pro go at high-speed with Draco at the center reveals over a dozen of these satellites over the course of just a few hours.

Some Light Non-Science Reading: Circle Templates – Know Your Field Of View!

As appeared in the May 2012 edition of the Syracuse Astronomical Society newsletter, the Astronomical Chronicle.

From the “why didn’t I think of that sooner?” department…

Binoculars are, far and away, the best way to start in observational astronomy (after you have some of the constellations figured out first, of course). The Moon reveals great new detail even at low magnification, the four Galilean Moons of Jupiter are obvious (when they’re not transiting or being “occulted” by Jupiter), all of the Messier objects are find-able (with a little practice and either lots of time or one lucky clear evening in March), and the sky becomes a busy highway of satellites that are otherwise too small to reflect significant light for naked eye viewing. Perhaps less pragmatically but nonetheless significant, the ownership of one simple, easy to produce, easy to use, easy to master piece of paired glassware connects you to the magnification-enhanced world of astronomy begun with Galileo, who used a much poorer quality and lower magnification telescope than those found in Big-Box Stores to forever and disruptively change how Western Civilization (and beyond!) placed itself in the Universe.

That all sounds profound I guess, but you’ve got a book open and are trying to keep track of a flashlight while keeping your arm still as you bounce your head back-and-forth in this really dense part of sky because you don’t know if you’re looking at M36, M37, or M38 in Auriga and you know you’ll NEVER find that part of the sky again. The, if you’ll pardon the expression, dark art of star-hoping is one that absolutely requires practice. More importantly, it requires having a proper frame of reference. I admit that I spent more than a few months with my trusty Nikon Action 12×50’s without ever actually having a handle on just how big the piece of celestial real estate I was staring at was.

It may seem obvious but is something you (well, I) didn’t think to use to your (well, my) immediate advantage. The magnification in the binos does NOT change! You are constantly looking at the same-sized region. This means that you can easily correlate magnification to real estate and know exactly what the limit of your in-eyepiece star-hopping is.

My solution, and one that is generally applicable to all your binoculars (and low-magnification eyepieces in your scope), was to buy an architects circle set. Yes, one of the green numbers with all the holes. If you have one book you’ve committed to (in my case, Sky And Telescope’s Pocket Sky Atlas, but I also have a copy of the Cambridge Star Atlas that hasn’t had its spine properly cracked yet), find some obvious star groupings, see how many of them you can get in your field of view, crack your book open to the right page, and overlay until your circle engulfs only what you see.

Simple! This simple tool dramatically improved my star-hopping aptitude. Keeping with my circumpolar theme this year, using the Sky Atlas and a pair of 12×50’s, I can just barely get the stars Mizar/Alcor and Alioth from the handle of the Big Dipper into the field of view – this corresponds to a 1.1250″ circle…

For the Cambridge Atlas, this same circle is 0.8125″…

I can plot the path to dim or densely-packed objects at leisure by finding bright stars or small groupings and “walking” my view along the path of overlaid circles, always knowing what I should and should not be seeing at any time (minus the odd planet, satellite, Milky Way supernova, etc.).

The same applies to scopes, although you’ll hit that smallest circle quickly (and you’ll find yourself having to flip/invert the image in the piece of paper)! My solution for that was to buy the BIGGEST eyepiece I could find to make sure I’m getting the LEAST amount of magnification. The circles get you to the object, then the magnification draws you in…

Some Light Science Reading. The Constellations: Orion

As first appeared in the April 2012 edition of the Syracuse Astronomical Society newsletter The Astronomical Chronicle (PDF).

Image generated with Starry Night Pro 6.

Much can be said about the old hunter Orion. To Central New York observers, it had (until very recently) been the case that Orion made his way across the Night Sky during the coldest and least hospitable (to most nighttime observers) months of the year. Conditions would keep observers in hiding from him (some of the best CNY observers I know would risk surgical strikes on the Orion Nebula with their fastest to set-up and tear-down equipment). The abbreviated winter of 2011/2012 and reasonably early start of the SAS observing season have provided us with excellent opportunities in the past few months to make Orion The Hunter now the hunted. The mid-April observing session will be the last “official” opportunity to observe Orion before he disappears behind the Western horizon until the most nocturnal of us can next see him in our Eastern sky before sunrise in late August. I then take this opportunity to discuss Orion, one many CNY/SAS members may know the best by sight but may know the least by observing attention.

One of the topics covered in the 2011 SAS lecturing series was how we observe. Not the discussion of optics or the physics of planetary motion along the ecliptic, but the visual and mental mechanisms we use to translate the photonic triggers in our retina into mental pictures of celestial objects. Orion was the astronomical example I used to describe Pareidolia, how we impose a kind of order on things we see despite that order not being present in the actual collection. When you look at a cloud, you may see a face, an animal, or something your mind triggers as being something it clearly is not. I often placed the infamous “Face On Mars” next to the Constellation Orion to show clearly how we see what we think we see despite all reasonable evidence to the contrary (or the two can be mangled together, as shown below). The clouds may look like an animal, the “Face On Mars” looks unmistakably like a shadowed face, and Orion, as it happens, has looked like a human figure to virtually all peoples for as long as we have record of Constellations, the same way Scorpius has appeared as a scorpion to every civilization for which this little monster was part of the local biosphere.

Pareidolia is not just for cognitive neuroscience! One of the keys to learning the sky I discussed last year was to let your mind wander while staring at the sky and see if certain things jump out at you. The constellations are, for the most part, made up of the most reasonably bright star groupings, but if you see any type of geometry that makes some part of the sky easy to identify, run with it. This same philosophy may be responsible for the rise of the asterism, or “non-Constellation star grouping,” as the distillation of mythological complexity into more practical tools for everyday living. For instance, I suspect everyone reading this can find the asterism known as the Big Dipper, but how many know all of the stars of its proper Constellation Ursa Major? Our southern tree line and Cortland obscure some of the grandeur of Sagittarius, which means we at the hill identify the location of its core (and several galactic highlights) by the easy-to-see “teapot.” The body of Orion is a similar case of reduction-to-apparent, as the four stars marking his corners (clockwise from upper left)…

Betelgeuse (pronounced “Betelgeuse Betelgeuse Betelgeuse!” – marking his right shoulder; a red supergiant of very orange-ish color even without binoculars)

Bellatrix – the left shoulder (so you now know the Constellation is facing us as originally defined) – a blue giant known also known as the “Amazon Star”

Rigel – the left foot; a blue supergiant and the star system within which the aliens that make the Rigel Quick Finder reside

Saiph – the right foot; a star dim in the visible but markedly brighter in the ultraviolet. Saiph and Rigel are about the same distance away (Saiph 50 light years closer at 724 light years, a point to consider as you observe them both)

… and the three stars marking his belt (from left)…

Alnitak – A triple-star system 800 light years away with a blue supergiant as its anchor star

Alnilam – the farthest star of the belt at 1359 light years, this young blue supergiant burns as brightly as the other two, making the belt appear equally bright “al across”

Mintaka – 900 light years away, this is an eclipsing binary star system, meaning one star passes between us and the main star in its orbit (about every 5.7 days)

… are obvious to all, while the head and club stars require a longer look to identify.

Sticking to Naked Eye observing for a moment, Orion is not only famous for its historical significance and apparent brightness. Orion is ideally oriented to serve as an order of alignment for several nearby Constellations and is surrounded by enough bright stars and significant Constellations that curiosity alone should have you familiar with this part of the sky in very short order. As an April focus, it is of benefit that all of the Constellations we’ll focus on either hit the horizon at the same time as Orion or they rest above him.

I’ve color-coded the significant stars marking notable Constellations in the image below. If you’re standing outside on any clear night, the marked stars should all be quite obvious (we’re talking a hands’ width or two at arm’s length). From right and working our way counterclockwise…

(RED) Following the belt stars to the right will lead you to the orange-ish star Aldebaran, marking the eye of Taurus the Bull. This is a dense part of the sky, as Aldebaran marks both the head of the Bull and also marks the brightest star in the Hyades star cluster (a gravitationally-bound open cluster 150 light years away composed of over 100 stars). Just to the right of this cluster is the “Tiny Dipper” known as the Pleiades (Messier 45), another dense star cluster worth observing at all magnifications. Both of these clusters are simultaneously easier and harder to find at present, as Venus (“1”) is resting just above them, providing an easy way to find both clusters but plenty of reflected light to dull the brilliance of the two open clusters.

(ORANGE) Auriga, featuring Capella (the third brightest star in the Night Sky), is an oddly-shaped hexagon featuring a small triangle at one corner. Auriga, like Ursa Minor in last month’s discussion, is made easy to find by the fact that the five marked stars are in an otherwise nondescript part of the sky (relatively dim generally, but brighter than anything in the vicinity). Venus will dull Hassaleh (Auriga’s closest star to Venus and the two open clusters below it) but Elnath and Capella will be easy finds.

(YELLOW) Castor and Pollux, the twins of Gemini, are literally standing on Orion’s club. Making an arrow from Mintaka (the right-most star of the belt) and Betelgeuse will lead you to Alhena (Pollux’s left foot), after which a slow curve in a horseshoe shape will give you the remaining stars.

(GREEN) Canis Minor is two stars (which is boring), but is significant for containing Procyon, the 7th brightest star in the Night Sky (which means it will be an EASY find). But don’t confuse it with Sirius, which is the big shimmering star in…

(BLUE) Canis Major is the larger of Orion’s two dogs and contains Sirius (“The Dog Star”), a star so bright (magnitude −1.46) and so close (8.6 light years) that it appears not as a star but as a shimmering light. Some would say an airplane, others would say a hovering UFO. Part of my duties as president involve intermittently explaining that it is not the latter.

And, with respect, Monoceros is an old Constellation but not a particularly brilliant one. Having Canis Minor and Canis Major identified will make your identification of Monoceros quite straightforward.

We now turn to the other “stellar” objects in Orion, composed of three Messiers and one famous IC. M78 is a diffuse nebula almost one belt width above and perpendicular to Alnitak. You will know it when you see it. M43 and M42 (marked as “4” in the image below), on the other hand, are so bright and close that you can see their nebulosity in dark skies without aid of any optics.

M42 – The Orion Nebula is, in the right dark conditions, a Naked Eye sight in itself. For those of us between cities, even low-power binoculars bring out the wispy edges and cloudy core of this nebula. For higher-power observers, the resolving of Trapezium at M42’s core serves as one of your best tests of astronomy binoculars (I consider the identification of four stars as THE proper test of a pair of 25×100’s. Ideal conditions and a larger aperture will get you six stars total). You could spend all night just exploring the edges and depths of this nebula. You can take a look back at the Astro Bob article in the April 2012 edition of the Astronomical Chronicle (From My Driveway To Orion, Nature Works Wonders) for a more detailed discussion of this part of Orion.

M43 – de Mairan’s Nebula is, truth be told, a lucky designation. M43 is, in fact, part of the M42 nebula that is itself a small part of the Orion Molecular Cloud Complex (not THAT’S a label). M43 owes its differentiation to a dark lane of dust that breaks M43 and M42, just as the lane of dust in our own Milky Way we know as the “Great Rift” splits what would otherwise be one continuous band of distant stars the same way a large rock in a stream causes the water to split in two and recombine on the other side.

Finally (and the one you’ll work for), IC 434, the Horsehead Nebula, lies just to the lower-left of Alnitak (1). The Horsehead is itself a dark nebula, a region absorbing light to make it pronounced by its difference from the lighter regions around it. To put the whole area into perspective, The Horsehead is itself STILL within the Orion Molecular Cloud Complex. The sheath of Orion’s Sword and nearly the entire belt is contained in this Complex, like dust being rattled off with each blow from Orion’s club.

I close by taking a look at the perilously ignored club attempting to tear into Taurus. At present, asteroids surround Orion’s Club like pieces of debris flying off after a hard impact. All are in the vicinity of 12th magnitude (so require a decent-sized mirror), and all are also moving at a sufficiently fast clip that their paths can be seen to change over several observing sessions (if, by miracle, enough clear days in a row can be had to make these measurements). I have highlighted the five prominent ones in the image below.

Is it an oddity to have Orion so full of asteroids? Certainly not! Orion is placed near the ecliptic, the apparent path of the planets in their motion around the Sun. Orion’s club just barely grazes the ecliptic at the Gemini/Taurus border, two of the 12 Constellations of the Zodiac, the collection of Constellations that themselves mark the ecliptic. As nearly all of the objects in the Solar System lie near or within the disc of the Solar System, you expect to find all manner of smaller objects in the vicinity of the Zodiacal Constellations. In effect, Orion’s club is kicking up different dust all year long as the asteroids orbit the Sun. You only have a few more weeks to watch the action happen before Orion’s return in the very early early morning of the very late summer.

– Happy Hunting, Damian