Messier Column July 2022

by Jim King

M87-M88-M89-M90.png

Charles Messier, in his active observation life, used several different telescopes.

Here follows a list of telescopes Messier listed and stated he used in 1765-69, published in the Connaissance des Tems for 1807 (here taken from Kenneth Glyn Jones' book; FL means "Focal Length", "Mag." Magnification, unfortunately he normally doesn't give the aperture):

  1. Ordinary refractor of 25 foot FL, Mag. 138x
  2. Achromatic refractor, 10.5 foot FL, owned by M. de Courtanvaux, Mag. 120x
  3. Achromatic refractor, 3.25 foot FL (Dollond), owned by Duc de Chaulnes, Mag. 120x
  4. Ordinary refractor of 23 foot FL, Mag. 102x
  5. Ordinary refractor of 30 foot FL, owned by M. Baudouin, Mag. 117x
  6. Campani refractor, owned by M. Maraldi, Mag. 64x
  7. Gregorian reflector ('Short') 6 feet FL, owned by M. Lemonnier, Mag. 110x
  8. Gregorian reflector 30 feet FL, 6 inch aperture, Mag. 104x
  9. Newtonian reflector 4.5 foot FL, Mag. 60x
  10. Refractor 1 foot FL, 3-inch aperture, owned by M. de Saron, Mag. 44x
  11. Refractor 19 foot FL, of the Paris Observatory, Mag. 76x

As there's always a magnification given, it seems that the idea of exchangeable eyepieces was not yet common in Messier's time.

Although some of Messier's reflecting telescopes had 7.5-to-8.0-inch aperture, they had little light gathering power as their mirrors were made of speculum metal (glass mirrors came in use only in the 1850s).

In his contribution to Sky & Telescope which is reprinted in Mallas' and Kreimer's Messier AlbumOwen Gingerich points out that Messier's favorite instrument was a 32-feet FL, 7.5-inch aperture Gregorian reflector with mag. 104x, not listed above. Bailly has computed that the effective aperture of this instrument was equivalent to a 3.5-inch refractor. Even worse was the situation of the old Newtonian reflector he brought over from Delisle, which was an 8-inch but as effective as a 2.5-inch refractor only, so it was little used, although it seems this was the "original" instrument at Hotel de Cluny, Messier's observatory. Later he preferred to use several 3.5-inch (90 mm) achromatic refractors, which were usually about 3.5 feet long and magnifying 120 times. He selected to use these scopes because they were the best accessible instruments for him.

It remains to state that all of Messier's instruments could probably not compete with a modern 4-inch refractor or 6-inch Newton reflector. Therefore, even moderately equipped amateurs of current days can easily hunt down all the objects he observed and cataloged.

(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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M88 Spiral Galaxy (Observability: Very Challenging*) M88 has been described as resembling the Andromeda Galaxy (M31).  M88 is one of the more conspicuous spiral systems in the Virgo cluster of galaxies.  Although it only shines at magnitude 9.5, its compact size and compact and 30-degree tilt from edge-on give good surface brightness at 22.3.

Stretching across 110,000 light-years of space, M88 is one of the largest spirals in the Virgo Cluster region.  It has well-organized dust lanes that form a prominent spiral pattern with many filamentary arms studded with knots. Beyond the dust, young and hot star clusters and hydrogen-rich star-forming regions line the arms.  To the southwest are a pair of detached outer arms.

Messier note: Observed March 18, 1781 “Nebula without a star in Virgo, between two faint stars and a sixth-magnitude star, which all appear in the same telescopic field as the nebula.”

NGC note: “Bright, very large, very much extended.” 

Data: Messier 88 aka NGC 4501

Con: Coma Berenices                                        Mag: 9.6

RA: 12h32.0m                                                   Dec: + 14.25

Dist: ~62 million light-years

 

M87 Elliptical Galaxy (Observability: Very challenging *) A monstrous ball of energy, the giant elliptical galaxy M87 measures ~115,000 light-years across and has a total mass of nearly 800 billion solar masses, making it one of the more massive galaxies known.  It is also one of the brighter ellipticals in the Virgo Cluster and one of the more luminous of all known ellipticals.  M87 is easily located by drawing a line from M58 to M84…M87 lies almost equidistant between them.  

The central member of the Virgo Cluster, M87 is a powerhouse with a very strong central radio source and a furious jet of matter blasting out from its nuclear region.  After studying Hubble Space Telescope images of M87, astronomers now believe that a black hole with a mass of ~3 billion solar masses lurks in the galaxy’s nucleus within a zone about 120 light-years across, making it the largest black hole known.

Messier note: Observed March 18th, 1781: “Nebula without a star in Virgo, below and quite close to an eighth-magnitude star. “

NGC note: “Very bright, very large, round, much brighter in the middle, third of three (easternmost).”

Data: Messier 87 aka NGC 4486

                        Con: Virgo                                            Mag 8.6

                        RA: 12h30.8m                                       Dec: +12.24

                        Dist.: ~55 million light years

 

M89 Elliptical Galaxy and M90 Mixed Spiral Galaxy (Observability: Very Challenging *) The Virgo Cluster harbors some 250 large galaxies and perhaps a thousand smaller systems. One distinguishing characteristic of this particular galaxy cluster is its smattering of spirals loosely dispersed among the more formless ellipticals, this peculiarity is nicely represented by the pairing of M89 and M90.  Appearing close together, both galaxies will fit into a low-power FOV of almost any amateur telescope. Although their magnitudes are similar, M90 is bigger, bolder, and more interesting than its counterpart.

M90 is one of the larger spirals in the Virgo Cluster, though it may be of low density.  It may also be a nearly perfect spiral. Though unusual, its shape could reflect an instance of near-perfect geometry, one where we see an elliptical system looking directly down its major axis. At a glance, we’re looking at a modest system, only about 50,000 light-years in true physical extent.  But images of M89 made in 1979 reveal that the galaxy is much larger than was previously believed.

The entirety of M89 is surrounded by a faint but significant outer envelope that reaches out to about 150,000 light-years.  It was the first galaxy to be discovered by such a feature.

Messier notes: M89.  Observed March 18th, 1781: “Nebula without a star in Virgo.  Its light is extremely faint and diffuse and only visible with difficulty” 

Messier notes: M90.  Observed March 18th, 1781: “Nebula without a star in Virgo Its light is extremely faint and diffuse.”

NGC note: M89.  “Pretty bright, pretty small, round, gradually much brighter in the middle.”

NGC notes: M90.  “Pretty large, brighter in the middle to a nucleus.”

Data: Messier 89 aka NGC 4552

                        Con: Virgo                                                         Mag 9.8

                        RA: 12h35.7m                                                   Dec: +12.33

                        Dist.: ~50 million ly

Data: Messier 90 aka NGC 4569

                        Con: Virgo                                                         Mag 9.5

                        RA: 12h36.8m                                                   Dec: +13.10

                        Dist.: ~40 million ly

* 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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