The Galaxies of Serpens Caput by Mark Bratton, Montreal Centre ([email protected])
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Scenic Vistas The Galaxies of Serpens Caput by Mark Bratton, Montreal Centre ([email protected]) xcept for the relative minority of Located on a line amateur astronomers who conduct joining beta and delta Esystematic scientific research with Serpentis, NGC 5970 is their telescopes, most of us are very much one of the brightest tourists in our approach to the universe. galaxies this region has We set up our instruments when our busy to offer. Located about schedules permit and are very much at eight arcminutes the mercies of the fickle nature of the southwest of a weather in these parts. Our time at the magnitude +8 field star, telescope is precious and we try not to this spiral galaxy is waste too much of it in fruitless pursuit oriented due east/west of unattainable objects. So we often stick and features a very to the tried and true, best exemplified by bright and small core the entries on the Messier list. embedded in a bright One of the reasons why I started bar oriented along the writing this column seven years ago was major axis. In my 15-inch my intention was to draw attention to reflector, this bar ap- interesting sights in the universe that pears quite mottled, would otherwise not be well-known. In and one’s attention is travel guides for tourists here on Earth, drawn to a brighter breathtaking scenery is often referred to condensation im- An ~8-arcminute Digitized Sky Survey1 field of Seyfert’s Sextet, a faint as a scenic vista, hence the name of this mediately east of the group of galaxies in Serpens Caput. series of articles. core. The outer envelope I especially like to feature appears poorly defined, evidence of the My 15-inch telescope brings out the faint, constellations that are sometimes outer spiral structure of the galaxy. oval outer envelope oriented north/south. overlooked as well. One of them is the At magnitude +12.5, NGC 5984 is Located just south of a line subject of this month’s column, Serpens one full magnitude fainter than the connecting an optical triple in the west Caput. preceding galaxy. An edge-on system and a bright, equal pair of stars in the This moderately bright zigzag of oriented southeast/northwest, the galaxy east, NGC 5936 is a bright, well-defined stars, wedged between Virgo in the west is moderately well defined and very slightly circular glow with a thin, fainter outer and Ophiuchus to the east, is the home brighter to the middle, though no bright envelope. Although no core is visible, the of the brilliant globular cluster M5; there core is visible. central region of this galaxy is quite are a number of rather bright galaxies in Three degrees north-northeast of granular in texture. the vicinity as well. Unfortunately, after the brilliant globular M5, the observer Easily visible even at 48×, NGC 5962 a spring spent viewing the galaxies of comes to NGC 5921. Deceptively listed is a bright galaxy, elongated west- Leo, Virgo, and Ursa Major, some amateurs at magnitude +11.4, this delicate barred- northwest/east-southeast. The outer have had their fill of this class of object, spiral galaxy is a tough catch in a small edges of this broadly-concentrated galaxy which may explain why this region is telescope; only the round brilliant core fade slowly into the sky background and sometimes neglected. will be easily visible in a field of faint stars. the central region is bright and fairly well- 1The Digitized Sky Surveys were produced at the Space Telescope Science Institute under U.S. Government grant NAG W-2166. The images of these surveys are based on photographic data obtained using the Oschin Schmidt Telescope on Palomar Mountain and the UK Schmidt Telescope. The plates were processed into the present compressed digital form with the permission of these institutions. 128 JRASC June / juin 2002 defined, brightening quickly to the core. There is a nice image of this galaxy in the fainter plume of material seemingly The preceding five galaxies are plotted Deep Space CCD Atlas: North, which shows connected to galaxy e. Deep photographs on the first edition of SkyAtlas 2000.0, the galaxy as a classic “theta-shaped” show luminous material connecting the but you will need the brand-new edition barred spiral with a faint outer ring. Also individual galaxies, and indeed five of the of this great atlas to locate the sixth galaxy of note is a bright, unequal pair of stars six objects have similar redshifts, in the in this article. just beyond the outer envelope of the range of 4000 to 4500 km s–1 in recession. Located immediately southwest galaxy, located just slightly north of east. The sixth object, labeled d in the photo, from kappa Serpentis, NGC 5996 is about A little fainter is NGC 6004, though has a redshift in excess of 19,000 km s–1. magnitude +12.8 and may pose a challenge 8-inch apertures should show it easily. It A chance alignment, or perhaps a galaxy for 8-inch and smaller telescopes. In my is quite round in appearance and brighter that is being ejected from the group as a 15-inch reflector, this was a round, to the middle with surprisingly well- whole? More study will be needed to moderately-bright galaxy, gradually brighter defined extremities. ascertain the nature of this group. to the middle. No core was visible and At magnitude 13.0, NGC 6008 is a On a typical night at Sutton, Quebec, the edges were diffuse. Unfortunately, somewhat more difficult object to track my 15-inch reflector was easily able to none of the delicate structure evidenced down. Even in my 15-inch reflector I found find a blur of light indicating the group’s in photos or CCD images is visible at the it rather faint and diffuse, best seen at a location at 146×. Higher magnification eyepiece, though if you have access to a magnification of 146×. The core appeared made the blur a little fainter but aided telescope larger than 15 inches, you might quite condensed, but only a little brighter resolution. The galaxy labeled e was easiest want to see if you can make out some of than the extremities and only the central to see, visible as a brighter bar of light this intriguing little galaxy’s barred-spiral region of this barred spiral galaxy was that may have also included the galaxy structure. visible. labeled b. I was also able to pick up the Because of the large number of bright A faint pair, likely beyond the grasp galaxy labeled a as a very faint patch of stars in the region, star hopping to any of telescopes smaller than about 12-inch light intermittently visible southwest of these galaxies is a relatively aperture, is NGC 6018 and NGC 6021. from the bar. The other members of the straightforward affair and a pleasant way They can both be seen in a high-power group, including the high-redshift galaxy, to seek out interesting fare on warm June field of my 15-inch reflector, oriented were beyond the grasp of my reflector on evenings. along a north/south line. NGC 6021 is this occasion. Afew of the fainter galaxies are not the brighter of the two and appears a little It is always interesting to go off the necessarily out of reach of 8-inch class more concentrated to the center. The beaten track from time to time when out telescopes and can be hunted down often galaxies are superimposed over the field observing. On nights when you are alone with success. I urge everyone to at least of the much fainter galaxy cluster Abell and can concentrate on the task at hand, attempt to track down Seyfert’s Sextet, 2147. a relatively unknown constellation like an odd specimen in the extragalactic zoo. The last group of objects under Serpens Caput is a fascinating region to The brightest of the fainter galaxies consideration this month is by far the explore. in Serpens Caput is NGC 6012, a prominent, most exotic. Seyfert’s Sextet is that class though ill-defined galaxy oriented north- of object known as a compact galaxy northwest/south-southeast. Oval in shape, group, and like many of the objects of its the edges fade uncertainly into the sky class, there is some question about whether Mark Bratton, who is a member of the Webb background. The central region is only a all members are related. The photo on Society, has never met a deep-sky object he little brighter to the middle and slightly the previous page shows five distinct did not like. He is one of the authors of Night elongated along the galaxy’s major axis. objects (labeled a through e) and a sixth Sky: An Explore Your World Handbook. June / juin 2002 JRASC 129.