Roaming the Deep Sky #3
The Leo Triplet
By Don Clouse
Three spiral galaxies in Leo, M65, M66, and NGC3628, known as the Leo Triplet, make a very nice low power field. M65 and M66 form the base of a near isosceles triangle with NGC3628 at the point. The group is located about 2.5 to 3.0 degrees south southwest of Theta Leonis, or Chertan (also known as Chort). The chart shows the location of the triplet in the eastern part of Leo. The nuclei of M65 and M66 are about 20’ apart. NGC3638 is about 35’ from both. All three are related, being members of the "Leo Cloud" of galaxies, about 31 million light years away. Other members of this group include NGC3489, NGC3593, NGC3596, and NGC3666. These galaxies are also shown on the chart. M65 is a type Sa spiral galaxy over 80,000 light years in diameter. It is listed with a magnitude of 10.3 and size of 7.4’x2.1’. M66, is slightly brighter at 9.7. Its apparent size, 6.8’x3.1’, is similar to that of its neighbor, M65. M66 is a type Sb spiral with somewhat distorted arms and, at around 75,000 light years, is somewhat smaller than its neighbor. NGC3628 is an edge-on Sc spiral of magnitude 10.3 and an apparent size of 11.1’x2. 2'.
The following descriptions are drawn from three observations each of M65 and M66 but only one of NGC3628. Sky conditions ranged from a limiting magnitude of perhaps the low 5’s at Long Run Park, to the high 5’s at Pat Peak’s site south of Shepherdsville, to 6 or so at Wyandotte Woods. I used my Celestron 8" SCT (f/10, focal length 2032mm) with a 35mm eyepiece (49-degree apparent field) yielding a 50.6’ true field with a magnification of 58x. I also used a 24mm eyepiece (51-degree apparent field) giving 85x and a field of 36.1’ (which is too small to encompass all three galaxies at the same time).
M65 shows an off center, broad, approximately 1.5’x1.5’, nucleus of even brightness. The galaxy appears about 6’x2’ in overall dimension, extending perhaps 3.5’ north of the core and 2.5’ to the south. At 85 power, a hint of mottling near the nucleus was detectable. At 5’x2.5’, M66 appears slightly smaller and slightly brighter than M65. The dimmer haze surrounding the core area drops off rapidly in brightness. NGC3628 is visible as a thin, straight steak of light. It appeared about 7.5’x1.5’ in size being brighter and wider in the middle. At 85 power, most of the 7.5’ length of the north edge of the galaxy appears quite sharp. This sharp boundary area marks the large central dust lane. I could not detect any portion of the galaxy north of the dust lane. These three galaxies all fit easily into a low power (58x) 50’ field of view. Three, softly glowing, spiral galaxies in the same field of view is quite a lovely sight indeed. Look for Leo and the Leo Triplet high in the southeast to south before midnight during April evenings. Clear Skies!
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