The immortal beast: the Bear is a great place to hunt for unusual galaxies and stars.
Yellow and gold 6th-magnitude stars 42 arcminutes (42') apart rest about 2[degrees] south-southeast of Upsilon and make a nearly straight line with it. Extending that line 1.5[degrees] will bring you to our first target, a colorful triple star. Its A and B components bear the designation [SIGMA]1402. This name indicates that the pair was discovered by the 19th-century German-Russian astronomer Friedrich Georg Wilhelm von Struve. My 4.1-inch (105-mm) refractor at 28x shows the gold, 8th-magnitude primary holding a wide, yellow, 9th-magnitude companion to the east.
The third star belongs to the pair GIR 2 AC, where GIR stands for Pierre Girard, the British amateur who reported it in the Webb Society's Double Star Section Circulars in 1996. The C component is a deep-yellow 10th-magnitude star lounging a lavish 2.2' south of the primary. According to the Tycho Double Star Catalogue (published by Claus Fabricius and others in 2002), this saffron gem is an excruciatingly close pair of matched suns measured just once--0.4" apart in 1991. There's even a chance that this star isn't really double. Can you confirm it? Arizona astronomer Brian Skiff recommends using a 16-inch or larger scope under very steady skies.
The lovely galaxy NGC 3079 sits 28' west-northwest of [SIGMA]1402. Its southern tip grazes a triangle of one 8th- and two 91/2-magnitude stars. In my little refractor at 47x, I see a nice spindle about seven times longer than wide. It tilts a little west of north and harbors a large, highly elongated core. The tiny companion galaxy NGC 3073 joins the scene at 87x, making a perfect playing-card diamond with three field stars. This galaxy appears faint and round when I use averted vision but disappears when I look straight at it. At 127x, a very faint star is pinned to the northern tip of NGC 3079.
In my 10-inch reflector at 202x, NGC 3079 seems flat along its western flank but bulges on the opposite side. The core is slightly mottled and contains a bright elliptical center engulfing a nearly stellar nucleus. NGC 3073 also hosts a tiny, brighter heart.
This galaxy pair is about 50 million light-years distant. NGC 3079 has an active nucleus that emits high-energy jets of particles powered by a supermassive black hole. A recent study indicates that these jets are encountering dense clouds of interstellar matter and blowing a lumpy, bipolar bubble of hot gas. Images recorded in the light emitted by ionized hydrogen and nitrogen show the bubble extending 3,500 light-years from the galaxy's core.
Now let's visit the fascinating binary star W Ursae Majoris, just 162 light-years away. Its components are so close together that they're pulled into teardrop shapes that actually touch! Both stars are yellow dwarfs, one a bit larger than our Sun and the other a little smaller. The conjoined stars whirl madly around each other every 8 hours, undergoing two eclipses 4 hours apart as they alternately pass in front each other.
What makes this spinning dumbbell so appealing is its continuous variation in brightness as it presents an ever-changing face to inquisitive skygazers. It takes only 2 hours for the pair to go from maximum to minimum brightness or vice versa. W UMa peaks at about magnitude 7.8 and dips to 8.5, the two minima being nearly equal.
To locate W UMa, sweep 1.2[degrees] west from NGC 3079 to an 8.0-magnitude star. Then hop 1.7[degrees] farther west to a 6.5-magnitude star, the westernmost and brightest in a parallelogram of stars measuring 1/2[degrees] north to south. The northern and southern stars in the figure are magnitude 8.9, a little fainter than W UMa at its minimum. W UMa is the eastern star. If you check from time to time, you should be able to catch these stars-that-kiss in their quick-change act.
Next we'll dig a little deeper, burrowing down to an asterism that John Chiravalle calls the Spade in his book Pattern Asterisms. A good target for a small telescope or large binoculars, it's conveniently located 1.6[degrees] southwest of Phi ([phi]) Ursae Majoris. The celestial shovel runs southeast to northwest and spans 1.1[degrees]. My 4.1-inch scope at 28x displays three stars in the handle and eight in the head.
Starting once again at Phi, slip 2.6[degrees] east-southeast to a pair of 7.8-magnitude stars with a 9.6-magnitude star half-way between them. The trio forms a slightly curved, southeast-northwest line 16' long. The flat galaxy UGC 5459 parallels this line 5' to the south. An 8.7-magnitude star tries to hide its southeastern tip. In my 10-inch reflector at 213x, the galaxy appears 2 1/2 long and very thin. Two faint stars sit 1 1/2 west of the northwestern tip.
Flat galaxies are nearly bulgeless spirals that appear thin because we view them virtually edge-on. Many of these galaxies have very low rates of star formation and often do not show the dusty dark lanes that characterize their more active cousins, such as the magnificent edge-on spiral NGC 4565 in Coma Berenices.
LET IT BREATHE
Large open star clusters and asterisms like the Spade are easiest to recognize when there's plenty of black space around them. So they usually look best at your telescope's lowest possible magnification.
Sue French welcomes your comments and questions at email@example.com.
Hunting the Bear in May Object Type Magnitude Size/Sep. [SIGMA]1402/GIR 2 Multiple star 7.7, 8.9, 9.6 32", 134" NGC 3079 Galaxy 10.9 7.9' x 1.4' NGC 3073 Galaxy 13.4 1.3' x 1.2' W Ursae Majoris Variable star 7.8-8.5 -- Spade Asterism -- 1.1[degrees] UGC 5459 Galaxy 12.6 4.0' x 0.5' Object RA Dec. [SIGMA]1402/GIR 2 [10.sup.h] [04.9.sup.m] +55[degrees] 29' NGC 3079 [10.sup.h] [02.0.sup.m] +55[degrees] 41' NGC 3073 [10.sup.h] [00.9.sup.m] +55[degrees] 37' W Ursae Majoris [9.sup.h] [43.8.sup.m] +55[degrees] 57' Spade [9.sup.h] [42.6.sup.m] +53[degrees] 17' UGC 5459 [10.sup.h] [08.2.sup.m] +53[degrees] 05' Angular sizes and separations are from recent catalogs. Visually, an object's size is often smaller than the cataloged value and varies according to the aperture and magnification of the viewing instrument. Right ascension and declination are for equinox 2000.0.
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|Title Annotation:||Deep-Sky Wonders|
|Publication:||Sky & Telescope|
|Date:||May 1, 2008|
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