Some Light Science Reading. The Constellations: Cygnus

As first appeared in the June/July 2010 edition of the Syracuse Astronomical Society newsletter The Astronomical Chronicle (PDF).

Constellation Map generated with Starry Night Pro 6.

Those in the vicinity of Manlius, NY are no doubt aware of the presence of Sno-Top (home of the best soft black raspberry in the area, IMHO) and the duck pond at town center(-ish). Those continuing just a tad further along Fayette Street (92, DeWitt-to-Cazenovia direction) also know that the swan population is localized to the higher pond near the Saucy Swan Restaurant (they do make for loquacious patrons). These facts, combined with the oppressive CNY heat of early July, made the choice of Cygnus the Swan obvious for this month’s constellation. Fittingly, Cygnus is an astronomical feast for naked eye, binocular, and telescope observers alike and, as it is half-way between horizon and zenith in early July in the early evening, it is strategically placed for accessibility with all manner of optics.

Cygnus is surrounded by several dangerous Constellations. The animal Constellations Draco, Velpecula, and Lacerta might enjoy freshly killed what the king Cepheus would otherwise enjoy glazed. The massive Constellation Pegasus is a problem in its own right. Trampled by horse is bad enough on the ground, but to have to avoid trampling by a flying one is another matter altogether. Lyra may be the only reminder to Cygnus of its terrestrial past, having been the instrument of choice for one of Cygnus’ human attributions (that man being Orpheus. See below). For those using only their free pair of 1×7 binoculars (that is, your pair of eyes), the cross that makes up the body and elbows of the wings of Cygnus are most obvious. The bright stars Deneb, Sadr, and Gienah (and the nearby Vega in Lyra, the easiest of the stars in this part of the sky to find starting at sunset) are perhaps most obvious, but the rest of the body is pronounced. As the evening progresses (and on reasonably clear nights), the most striking feature of Cygnus is the river of stars and interstellar dust that is our view of the Milky Way (as if Cygnus is flying above it).

As a collection of prominent stars within the body of the Milky Way, you can guess that the Constellation we know as Cygnus has a long and distinguished history. The Greeks (“Give me a Constellation, any Constellation, and I show you that the history of that Constellation is Greek”) have many swans in their mythology, from Zeus (who fathered Gemini and Helen of Troy disguised as a swan, or so the story goes) to Orpheus (turned into a swan upon his death and placed next to his lyre (Lyra) to characters in Ovid‘s Metamorphoses. Cygnus is a member of the “Famed 48,” the 48 original Constellations contained within Ptolemy‘s Almagest.

Alberio. From wikipedia.org.

At the head of Cygnus is the star Alberio which, upon inspection with even low-magnification optics, resolves into two stars that make up quite possibly the best color contrast in the northern hemisphere (above, from wikipedia). Alberio A (the orange-ish one), is actually itself a true binary, meaning its two stars are gravitationally bound to one another. It is possible, with scopes larger than 20″ and under excellent conditions, to resolve the two stars, Alberio B (the blue-ish one), is a single star that is not gravitationally bound to Alberio A, making this most famous binary an “optical binary,” one where the two stars look very close but only because of our perspective from Earth. If Cygnus is out, this star always makes its way into the eyepiece of the 16″ scope at Darling Hill. Further, for those who like to get their scopes perfectly focused (especially large binoculars), this combination is an excellent test.

M29. From wikipedia.org.

As is the case with all of the Constellations within the band of the Milky Way, Cygnus is host to several binocular and telescope objects. The two pronounced Messier Objects are M29 and M39, both open clusters. M29 (above, from wikipedia) is famous (to me) for being the one Messier Object that does NOT appear in the index of the Peterson Field Guide To Stars And Planets. Believe me, I have tried several times to find it (just assuming the dark conditions kept me from seeing it. It does appear in the Constellation map, though). This object appears within the binocular field of view of Sadr and is small but worth scanning in dark skies. M39 (below, from seds.org) is similarly nondescript, residing between Deneb and the stars of Lacerta.

M39. from seds.org.

Cygnus becomes quite interesting for its wealth of interesting New General Catalogue (NGC) Objects. The four most prominent objects are the North America Nebula (NGC 7000), the Pelican Nebula (IC 5070), the Veil Nebula (NGC 6960, 6962, 6979, 6992, and 6995), and the Crescent Nebula (NGC 6888). The North America (not American) Nebula (below, with the Pelican Nebula to its right, from wikipedia) is a testament to the only mild imagination of the working observational astronomer. Like many nebulae, details can be pulled out of this object with the use of filters. Depending on the conditions, the best way to confirm this structure exists in your scope is, frankly, to move the scope ever so slightly in the field of view of nearby stars and confirm for yourself that some slightly darkened patch of sky is staying put with respect to the background of stars. This approach, combined with averted vision, is definitely my method of choice for finding the locations of objects I may otherwise miss completely (and we’ve all had the experience of NOT seeing something in a scope that another person can even make detail out of). The very low surface brightness of the nebula makes it an at-least binocular object to observe, but it is noteworthy that this entire North America Nebula is reportedly four times the size of the full Moon. The Pelican Nebula (lower right of the image above) looks more like a Teradactyl to me, but there is some similarity in both (in case you do not see it, the pair of eyes are at upper left (with a bright star in each marking the pupils), the beak extends to the left (and is narrower than a typical pelican), and the body extends to some less structured arrangement down to the lower right).

The North America and Pelican Nebulae, photo by Jason Ware. From wikipedia.org.

The Veil Nebula is a collection of nebulae that make for haunting photos. I am very pleased to have a greyscale image of the Eastern Veil provided by our own Stu Forster (below and in the member gallery). This object is very difficult to observe without an OIII filter, but even an 8″ scope will resolve the detail of this nebula with the filter (it is reported that in excellent sky locations, simply holding this filter to one’s eye will make the Veil Nebula stand out). The Veil Nebula has also been the focus of some considerable Hubble imaging time and a web search for these images is definitely worth one’s time.

The Crescent Nebula. Photo by Stu Forster.

Finally, the Crescent Nebula has also been the focus of some astrophotography time by the good Dr. Forster (below (The Crescent, not Dr. Forster)), appearing to me more like a floating brain than a boring crescent. The Nebula is formed by a Wolf-Rayet star, a type of very hot, massive star with a strong stellar wind. This nebula is actually a double-whammy, as the fast-moving stellar wind from this WR star is colliding with the slower stellar wind from this same star when it was a red giant some 400,000 years earlier.

The Crescent Nebula. Photo by Stu Forster.

Clear skies, Damian

Some Light Science Reading. The Constellations: Sagittarius

As first appeared in the July 2009 edition of the Syracuse Astronomical Society newsletter The Astronomical Chronicle (PDF).

Image generated with Starry Night Pro 6, www.starrynight.com.

The Constellations, for all of their mythological, mystical, and ceremonial significance throughout human history, are also the bases for much of the scientific discovery (the Zodiac was a calendar long before it was ever used to identify the other kind of dates, and the backdrop of the unchanging Heavens served as the guide against which the motions of the planets were first tracked) that fueled our understanding of the universe before Edwin Hubble first exposed its true vastness by identifying the “Andromeda Nebula” as, in fact, a galaxy far outside of the Milky Way. The constellations have also served in a far more pragmatic capacity throughout human history as seasonal sign posts, simply marking times and locations for those on land and sea. Perhaps the most famous example of this in American History is the use of the Big Dipper as the marker by freed slaves traveling North along the Underground Railroad. The song “Follow the Drinkin’ Gourd” is not simply a series of verses, but is instead a set of instructions, with the “Drinkin’ Gourd” being the Big Dipper, the most easily recognizable asterism in the Northern Hemisphere (amateur astronomer or not) and pointer (by drawing an arrow from Merak to Dubhe) to the North Star Polaris, itself the most famous star of the Little Dipper (also known as Ursa Minor), an otherwise somewhat unimpressive constellation (certainly not as prominent in the North as the Big Dipper or the Cassiopeia “W” and, therefore, not as useful a sign post).

The Little Dipper is not the most prominent constellation in the Night Sky, but it serves as an important terrestrial marker because it includes Polaris among its member stars. Just as the Big Dipper is a prominent asterism that directs you to the Little Dipper, the Summer constellation Scorpius (which has been recognized specifically as a scorpion by many cultures for several millennia) can draw you to a slightly less prominent constellation to its West that is a sign post to a far more impressive marker than Polaris.

Sagittarius is an astronomy instructor’s dream constellation, as it wraps up a number of interesting topics of discussion in one easy-to-find location. To begin, the Centaur, a half-human/half-horse hybrid, is the perfect bridge between the fantastical world of mythology in all of its seeming ridiculousness and, well, the shining example of what might even be ridiculously possible as scientists learn more about DNA and biological engineering (as of this past May, we now can make monkeys that glow in the dark. That’s right, in the dark).

Second, Sagittarius provides its viewer another shining example of the difference between a constellation and an asterism. A constellation is, simply, a specific grouping of stars that everyone has agreed are, in fact, assigned to that particular constellation. This circular definition was finally laid flat by the International Astronomical Union in its defining of Constellation Boundaries, solidifying star groupings that go as far back as antiquity and as far forward as 1763 (the exploration of the Southern Hemisphere was not limited to the land and the sea). An asterism is, simply, a convenient grouping of stars that are NOT one of the 88 Official Constellations, with some asterisms being only fragments of a full Constellation (such as the Big Dipper, the most famous asterism in the Constellation Ursa Major) and some asterisms composed of parts of multiple Constellations (such as the Summer Triangle, composed of the stars Deneb (Cygnus), Altair (Aquila), and Vega (Lyra). At our latitude (Syracuse and Tully), we cannot even see the entire Constellation of Sagittarius, but have an excellent view during the Summer of one of the most modern of conveniences in the form of a Tea Pot (see below). We may seem a little ridiculous pointing out the tea pot, short and stout, with its handle (on the left or to the West) and its spout (on the right or to the East) at Darling Hill on a dark night, but you will not forget this asterism after it jumps out at you the first time. An important thing to remember is that any grouping of stars in the sky that helps YOU find what you are looking for is as significant an asterism as one you might find in any book. If an otherwise unlabeled grouping jumps out at you that helps you find your place in the Night Sky, put those informal naming rights to good use.

Image generated with Starry Night Pro 6, www.starrynight.com.

Third, the billowing steam from the spout of this tea pot marks a most important location to all 100 billion or more stars in our galaxy. The small darkened oval in the picture above marks the exact location of the center of the Milky Way galaxy (the tiny, fuzzy spec at its middle), meaning we are looking into the most dense region of the galaxy when we set our gazes at this region. Unfortunately, the city lights from Cortland wash the density of the Milky Way band at our South when we observe in Tully, although the full band of the Milky Way is prominent above us during the Summer.

Images from ircamera.as.arizona.edu.

Fourth, because we are looking into the heart of the Milky Way when we see the spout of the tea pot (as the image at right tries to show), we are looking into the densest region of stars we can see from Earth. As a result, this tea pot marks the location of a variety of Messier Objects and fainter nebulae far more numerous than even the largest variety pack the other Celestial Seasonings (pardon the tea pun) has to offer. The Trifid Nebula (M20), Lagoon Nebula (M8), Sagittarius Cluster (M22), Omega Nebula (M17), Black Swan Nebula (M18), M25, M23, M55, M54, M70, M28, M21, and M75 all reside within the Sagittarius boundary, while M6, M7, M16, and a host of other deep sky objects surround its borders in neighboring Scorpius, Ophiuchus, and Serpens Cauda.

When we observe during the Summer, I often recommend to new visitors with binoculars to simply point to the South, aim for the tea pot, and slowly scan. If your binoculars or telescope are anywhere near focused, you are guaranteed to find something within your field of view.

Mildly thirsty just thinking about it,
Damian

www.syracuse-astro.org
en.wikipedia.org/wiki/Constellation
en.wikipedia.org/wiki/Zodiac
www.match.com
en.wikipedia.org/wiki/Planets
en.wikipedia.org/wiki/Edwin_Hubble
en.wikipedia.org/wiki/Andromeda_Galaxy
en.wikipedia.org/wiki/Milky_Way
en.wikipedia.org/wiki/American_History
en.wikipedia.org/wiki/Big_Dipper
en.wikipedia.org/wiki/Underground_Railroad
en.wikipedia.org/wiki/Follow_the_Drinkin%27_Gourd
en.wikipedia.org/wiki/Northern_Hemisphere
en.wikipedia.org/wiki/Beta_Ursae_Majoris
en.wikipedia.org/wiki/Dubhe
en.wikipedia.org/wiki/Polaris
en.wikipedia.org/wiki/Little_Dipper
en.wikipedia.org/wiki/Cassiopeia_(constellation)
en.wikipedia.org/wiki/Scorpius
en.wikipedia.org/wiki/Sagittarius_(constellation)
en.wikipedia.org/wiki/Centaur
www.huffingtonpost.com/2009/05/27/glowing-baby-monkeys-marm_n_208296.html
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en.wikipedia.org/wiki/List_of_constellations
en.wikipedia.org/wiki/Southern_Hemisphere
en.wikipedia.org/wiki/Asterism_(astronomy)
en.wikipedia.org/wiki/Summer_Triangle
en.wikipedia.org/wiki/Deneb
en.wikipedia.org/wiki/Altair
en.wikipedia.org/wiki/Vega
en.wikipedia.org/wiki/Sagittarius_(constellation)
en.wikipedia.org/wiki/Messier_20
en.wikipedia.org/wiki/Messier_8
en.wikipedia.org/wiki/Messier_22
en.wikipedia.org/wiki/Messier_17
en.wikipedia.org/wiki/Messier_18
en.wikipedia.org/wiki/Messier_25
en.wikipedia.org/wiki/Messier_23
en.wikipedia.org/wiki/Messier_55
en.wikipedia.org/wiki/Messier_54
en.wikipedia.org/wiki/Messier_70
en.wikipedia.org/wiki/Messier_28
en.wikipedia.org/wiki/Messier_21
en.wikipedia.org/wiki/Messier_75
en.wikipedia.org/wiki/Messier_6
en.wikipedia.org/wiki/Messier_7
en.wikipedia.org/wiki/Messier_16
en.wikipedia.org/wiki/Scorpius
en.wikipedia.org/wiki/Ophiuchus
en.wikipedia.org/wiki/Serpens_Cauda