M65, M66 and NGC 3628 - The Leo Trio

Designations:	M65, NGC 3623
Object Type:	Spiral Galaxy
Constellation:	Leo
RA:	11 hr 18.9 min	Dec:	+13&Deg; 05 min
Magnitude:	9.3 (SB 12.4)	Size:	9.8 X 2.9 arcminutes
Distance:	24 million light years
Discoverer:	Pierre Mechain, 1780

Designations:	M66 / NGC 3627
Object Type:	Spiral Galaxy
Constellation:	Leo
RA:	11 hr 20.2 min	Dec:	+12° 59 min
Magnitude:	9.0 (SB 12.5)	Size:	9.1 X 4.1 arcminutes
Distance:	21.5 million light years
Discoverer:	Pierre Mechain, 1780

Designations:	NGC 3628
Object Type:	Spiral Galaxy
Constellation:	Leo
RA:	11 hr 20.3 min	Dec:	+13° 35 min
Magnitude:	9.5 (SB 13.7)	Size:	14.8 X 3.3 arcminutes
Distance:	25 million light years
Discoverer:	William Herschel April 8, 1784

Leo's M65 and M66 probably rank second only to M81 and M82 as sought-after galaxy pairs. Located about halfway between Theta and Iota Leonis and separated by only 21 arc minutes, M65 and M66 are both visible in 7X35 binoculars - as is a larger, fainter edge-on galaxy - NGC 3628 (not shown) - just 35 arc minutes north-northeast of M66. Through a 4-inch refractor, all three galaxies vie for attention in the same low-power field. These three galaxies may be part of an independent cluster of galaxies on the near edge of the vast Virgo Cloud. M65 is a joy to see but an awfully difficult galaxy to observe. The details within its bright, nearly edge-on disk vary only slightly from the background brightness, so they're hard to pick out from the "noise". M66 appears very soft and graceful; it's nothing like the strong and dynamic image you see in photographs. The galaxy's bright, starlike nucleus is its most noticeable feature. Use low power to compare the cores of M65, M66 and NGC 3628. M65 has a somewhat stellar nucleus, and NGC 3628 reveals absolutely nothing! Now look for a bright knot immediately northwest of M66's nucleus. A dark patch lies east of the knot, followed by a mere stump of a spiral arm. The region surrounding the nucleus is oval shaped and oriented southeast to north-west. See if your eye doesn't catch a streak of light running off to the south. The orientation of this streak can help you determine the galaxy's spiral pattern. The rest of the details are a chaotic mix of faint streaks of dark and light. But don't let this confusion deter you from drawing the detail, because, if you look at the photograph, the galaxy really is a dizzying world of curdled starlight. The dust lying in the plane of NGC 3628 is dense and was certainly dense enough to veil the object from the keen eyes of Pierre Mechain, who discovered M65 and M66 in 1780. And while NGC 3628 is only 0.5- magnitude fainter than M66, the galaxy is larger, so it has a lower surface brightness (13.7 vs 12.5 respectively). NGC 3628 belongs to the Leo Spur of Galaxies. It has a linear diameter of 78,000 light years and a total mass of 135 billion Suns. The galaxy is not without its peculiarities. For instance, it has two equatorial planes, marked by dark matter tilted a few degrees to each other and the ends of the spiral arms are obviously warped, with evidence of star formation. The galaxy's bright bulge also has an unusual "peanut" shape, which is most likely the result of gravitational interactions with M65 and M66 as the three galaxies orbit on another. Then again, one theory of "peanut" galaxies is that they are simply barred spirals seen edge-on. Otherwise, it's an eye-for-an-eye relationship, whereby the three members are simultaneously distorting each other over time. CCD images have also revealed a 260-light-year-long stellar trail or plume extending to the south from NGC 3628 - another product of the tidal effects. This plume consists of clumpy star-formation regions that are roughly a hundred million years in age.

Telescope:	TMB 152 F8 APO refractor
Focal Length:	1201mm (961 mm with 0.8x focal reducer)
Mount:	Mountain Instruments MI-250 mount
Camera	SBIG ST10XME
Guider:	SBIG ST402ME
Exposures:	13 8-minute Luminance exposures and 5 8-minute exposures for each color (red, green and blue). Total time: 3 hours and 44 minutes
Location:	Cicero, IN
Software:	CCDSoft for image acquisition, processed with CCDStack and Photoshop CS2