Messier Column June 2022

by Jim King

I find myself compelled to once again, give credit where credit is due.  While Charles Messier basks in the glow of his famous catalogue of non-comets, he had help!  During his collaboration with Messier, Pierre Mechain added 25 or 26 objects to Messier’s catalogue (depending on how one looks at M102).

These include Messier’s 63,72,74,75,76,77,78,79,85,94,95,96,97,98,99,100,101, 102(?), 103, 104, 105,106,107,108,109… a sizable addition to Messier’s work.

Pierre Méchain was born in Laon, the son of the ceiling designer and plasterer Pierre François Mechain and Marie–Marguerite Roze. He displayed mental gifts in mathematics and physics but had to give up his studies for lack of money. However, his talents in astronomy were known to Jerome Lelande, for whom he became a friend and proof-reader of the second edition of his book "L'Astronomie". Lalande then secured a position for him as assistant hydrographer with the Naval Depot of Maps and Charts in Versailles, where he worked through the 1770s engaged in Hydrographic work and coastline surveying. It was during this time—approximately 1774—that he met Charles Messier, and apparently, they became friends. In the same year, he also produced his first astronomical work, a paper on an occultation of Aldebaran by the Moon and presented it as a memoir to the Academy of Sciences.

In 1777, he married Barbe-Thérèse Marjou whom he knew from his work in Versailles. They had two sons: Jérôme, born 1780, and Augustin, born 1784, and one daughter. He was admitted to the French Académie des Sciences in 1782, and was the editor of Connaissance des Temps from 1785 to 1792; this was the journal which, among other things, first published the Messier Objects. In 1789 he was elected a Fellow of the Royal Society.

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(An important jargon jogger:  Messier uses the descriptive term “nebula” since he was frequently using a 3.5-inch telescope which had difficulty resolving dim stars.  It appears that he thought “nebulae” were not gas clouds, but simply unresolved star clouds.  Therefore, in our descriptions, we must mentally separate Messier’s “nebulae” from the real thing.  He does differentiate nebulosity from luminosity.)

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M69 Globular Cluster (Observability: Apparent*) M69 is a sizable cluster some 80,000 light-years in true physical extent.  It lies only about 5,500 light-years from the Galactic center and is considered part of the Galactic Bulge.  Studies of M69 may be of importance in that the evolution of the bulge is not well understood.  Existing competing theories cannot explain why our bulge is dominated by old, metal-rich stars.

220526km_M69_M70_km-for-jking.png

Messier note: Observed August 31, 1780.  “Nebula without a star in Sagittarius, below the left arm and close to the bow.  Nearby is a ninth-magnitude star.  The luminosity is very faint and can be seen only under good conditions” … and any ambient light can cause it to disappear (added comment).

NGC note: “Globular cluster, bright, large, round, well resolved, stars of 14th to 16th magnitude.”

Data: Messier 69 aka NGC 6637

Con: Sagittarius                                                 Mag: 7.7

RA: 18h31.4m                                                   Dec: - 32.21

Dist: ~28,700 light years

M70 Globular Cluster (Observability: Apparent *) Although M70 lies at about the same distance as M69 and is slightly smaller (70,000 light-years across in true physical extent), it is approaching us five times as fast - 136 miles pr second versus 25 miles per second.  Like M69, it is a Galactic bulge globular, lying about 7,000 light years from the Galactic center.  

Over time, the core has tended to compress inward (collapse) while its halo expands outward.  What we see in the end is an expansive globular, with a small and intensely dense and bright core.  Only about 20 percent of the 150 or so known globulars have experienced collapse.

Messier note: Observed August 31, 1780: “Nebula without a star, close to M69 and on the same parallel. Nearby there is a 9th-magnitude star and four faint, telescopic stars almost in a straight line. “

NGC note: “Globular cluster, bright, pretty large, round, gradually brighter in the middle, stars from 14th to 17thmagnitude.”

Data: Messier 70 aka NGC 6681

                        Con: Sagittarius                                     Mag 7.8

                        RA: 18h43.2m                                       Dec: -32.18

                        Dist.: ~29,300ly

 

M80 Globular Cluster (Observability: Apparent) * M80, if it were not included in the Messier objects, would likely be overlooked by most astronomers.  M80 is a tiny globular cluster with an extremely dense central core and a spherical halo.  The owner of a rich-field telescope will be truly rewarded by the sight of M80’s thick pack of 7th-magnitude starlight glistening from amid the galactic pandemonium. 

220526_M80_km-for-jking.png

Messier notes: Observed January 4th, 1781: “Nebula without a star in Scorpius.  This nebula is circular; the center is bright and resembles the nucleus of a small comet, surrounded be nebulosity.” 

NGC note: “Remarkable globular cluster, very bright, large, very much brighter in the middle (variable star), readily resolved, contains stars of the 14th magnitude and fainter.”

Data: Messier 80 aka NGC 6093

                        Con: Scorpius                                                    Mag 7.3

                        RA: 16h17.0m                                                   Dec: -22.58.5

                        Dist.: ~32,600 ly

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* Sky Tools software offers an observability scale of 1 – 6, with 1: Obvious; 2: Easy; 3: Apparent; 4: Difficult; 5: Challenging; and 6: Very Challenging.  The rating scale I use is based on a Celestron SCT 8 Evolution telescope at the HAS dark site on a moonless night. 

Finito!

Ex astris, scientia, y’all!

Jim King

Want more? Check out the HAS website under “Programs”/Messier Challenge/HAS 45

 

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