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Let's even the score with M102

Though most lists of Messier objects contain 109 targets, the inclusion of NGC 5866 brings the total to an even 110.
ChapleGlenn

I hate odd numbers! If I’m putting gas in my car and the pump stops at $23.87, I’ll squeeze out enough gas to make it an even $24.00. When I’m out fishing and keeping a count of my catch, I’ll stubbornly keep casting until I’ve reached an even 10 or 20. Three Little Pigs? Bah! I would have added a fourth and housed him in a two-story, steel- and cement-reinforced condo.

I’m the same with sports stats, particularly baseball. I wince when a pitcher finishes the season with 19 wins or a batter ends up hitting .299. If only they had wound up with an even 20 wins or a .300 batting average! Last year, Miami Marlins outfielder Giancarlo Stanton hit 59 home runs. Were I the Major League Baseball commissioner, I would have extended the season until he hit No. 60.

When it comes to the Messier catalog, I’m also odd-number phobic. After all the historic studies and revisions, Messier’s number stands at 109 — but I round up to 110. (This is also why I selected 110 stellar duos for my Double Star Marathon.) And though I’m not alone in citing 110, most of the Messier lists that do recognize 109 objects (including the one used by Astronomy) discard M110 — a late addition that elevated one of the bright satellite galaxies of M31 to Messier status.

Other Messier lists fall short of 110 entries because of the controversy over the existence of Messier 102, which was reported by Messier’s contemporary Pierre Méchain early in 1781. Méchain later retracted his discovery, stating that it was a duplicate observation of M101.

But was it? In his original notes, Méchain described his find as a “nebula between the stars Omicron Boötis and Iota Draconis.” It’s possible that Méchain meant Theta Boötis, not Omicron. The Greek letters omicron and theta (ο and θ, respectively) look similar. Omicron Boötis is more than 40° away from Iota Draconis, while Theta Boötis lies about 11° to the southwest. And, lo and behold, if you look about one-third of the way from Iota Draconis to Theta Boötis, you’ll come across the 10th-magnitude galaxy NGC 5866. This is quite likely the object Méchain found.

ASYGC0618
This image of M102 (the Spindle Galaxy) was created by combining 60 minutes’ worth of sub-exposures taken with a 32-inch f/6 telescope.
Mario E. Motta, M.D.
A detailed article on the M102 controversy, written by Hartmut Frommert, appears on the SEDS Messier website at www.messier.seds.org/m/m102d.html. In it, Frommert presents a compelling argument that NGC 5866 is indeed Messier’s 102nd object. My argument is far more simplistic. NGC 5866 (an even number, by the way) brings the Messier catalog total to 110 — even number perfection!

One of my first goals as a fledgling backyard astronomer was to notch all the objects in the Messier catalog. M102 was one of the last. I captured it the evening of July 25, 1978, with a 3-inch f/10 reflector and a magnifying power of 30x. Next to a sketch of the galaxy, I wrote, “With averted vision, surprisingly easy! Accompanied by a star of ~11th magnitude. Slightly oval, it seems.” At the time, I was observing under 6th-magnitude skies.

Working with slightly murkier magnitude 5 skies three decades later, I revisited M102, this time with a 4.5-inch f/8 reflector and a 150x eyepiece to improve contrast. The galaxy was still visible, as was its long oval form. This shape, being wider in the middle, has garnered NGC 5866/M102 the nickname the “Spindle Galaxy.”

To Méchain and Messier, that nebula near Iota Draconis was little more than a fake comet. To me and my little backyard scopes, it was a patch of faint fuzz. However, it means much more to astronomers who have studied it with larger and more sophisticated telescopes. M102 is actually an edge-on lenticular galaxy bisected by a distinct dark dust lane. The dust lane gives M102 a striking photographic resemblance to another dusty edge-on galaxy, M104, the Sombrero Galaxy. 

Further study adds an awe-inspiring dimension to the 4.5'-by-2' patch of fuzz that is M102. It lies some 50 million light-years away, which translates to a true diameter of roughly 60,000 light-years. When you peer into the eyepiece, the light you’re seeing first left M102 during Earth’s early Eocene epoch, when our planet was embraced by a pole-to-pole tropical climate. Ancestral whales were in the process of abandoning a terrestrial existence, horses were dog-sized and had padded feet, and human ancestors were little more than tree-dwelling primates. Had Messier and Méchain known this, they might have abandoned comets and turned their attention solely to nebulous objects that didn’t change position.

Questions, comments, or suggestions? Email me at gchaple@hotmail.com. Next month: Another messy Messier mystery. Clear skies!

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