To give credit where credit is due, Time to ‘fess up: I really wish I were skilled and experienced enough to come up with this column on my own. But the truth is, in May 2019, I had the happy opportunity to spend some time visiting with Stephen James O’Meara as a guest of our own Goldbergs at their home here in Houston. For those of you who don’t know of him, Stephen is an accomplished and highly-skilled astronomer and author of international fame. He has a column published every month on visual observing in Astronomy magazine. For those of you who don’t know Amelia and Steve Goldberg (long-time members of HAS), they are quite accomplished and celebrated astronomers in their own right and are genially nice people.
I have two of Stephen’s Deep-Sky Companions books in my library, The Messier Objects and The Caldwell Objects which he graciously autographed for me. The Messier Objects is my primary source for this column. Frankly, it is a bit of a challenge to pick out gems to share here when each object is so full of jewels of amazing information and my space is so limited. For anyone who is into Messier or Caldwell, or wants to be, these books provide an excellent compendium of facts about the objects, interesting side-lights and back-stories, and insights into these great astronomer’s minds.
Last month, we finished up the Messier summer objects. Now we move into the fall and early winter group with its wide variety of wonders.
(An important jargon jogger: Messier uses the descriptive term “nebula” frequently since he was using a small 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 “nebulas” from the real thing. He does differentiate nebulosity from luminosity.)
M57 Planetary Nebula (2) easy *
“Among the curiosities of the heavens should be placed a nebula that has a regular, concentric, dark spot in the middle. – William Herschel”
When a star with a mass similar to that of our Sun nears the end of its life, it blows off a shell of gas that, from our perspective, appears like a ring centered around the dying star. M57, the Ring Nebula, represents the remains of one such disgorging episode about 7,000 years ago. The second planetary nebula discovered by Messier, it has worked its way ever since into the hearts of virtually all telescopic observers.
Messier note: (Observed January 31, 1779) Patch of light discovered while observing the Comet of 1779, which passed very close. It seemed this patch of light, which has rounded borders, must be composed of very faint stars. It has not, however, been possible to see them, even with the best telescopes, but the suspicion remains there are some.
NGC note: A magnificent object, annular nebula, bright, pretty large, considerably extended.
Data: Messier 57 aka the Ring Nebula aka NGC 6720
Con: Lyra Mag: 8.8
RA: 18h53.6m Dec: -+33.02
Dist: ~2,000 ly
M27 Planetary Nebula (2 easy) *
Although no star in Vulpecula shines brighter than magnitude 4.4, this summer constellation does boast the most famous of planetary nebulae, M27, the Dumbbell Nebula. Its physical diameter of 2.8 light years, also makes it one of the largest nebulae. The gaseous matter was blown from the blue dwarf star now at its center during the star’s death throes some 48,000 years ago. This makes M27 more than twice as old as typical planetaries. M27 is a cylindrical, multi-shelled planetary with different ionization structures seen at its equatorial plane; in fact, M27 is one of the few to have a triple shell.
Messier notes: (Observed July 12, 1764) Nebula without a star, discovered in Vulpecula, between the two forepaws, and very close to the fifth-magnitude star Flamsteed 14 in that constellation.
NGC notes: Magnificent object, very bright, very large, binuclear, irregularly extended.
Data: Messier 27 aka The Dumbbell Nebula aka NGC 6853
Con: Vulpecula Mag 7.3
RA: 19h59.6m Dec: +22.43
Dist.: ~1,200 ly
M71 Globular Cluster: (2) easy*
M71 was once of object of controversy among professional astronomers. Some argued that it is a loose globular, while others claimed it’s an extremely dense open cluster. There is no doubt today that M71 is globular. In fact, it is a very near one, being only 13,000 light-years distant, which is why it is so easily resolved and appears to lack the dense center typical of more distant globulars.
This great ball of ancient stars, some 27 light-years across, presently resides about 21,800 light-years from the Galactic center. We see it receding from us in its orbit around the Galaxy at about 14 miles per second.
Messier notes: (Observed October 4, 1780) The light is very faint and contains no stars. The slightest illumination causes it to disappear.
NGC note: Cluster, very large, very rich, pretty much compressed, stars from 11th to 16th magnitude.
Data: Messier 71 aka 6838
Con: Sagitta Mag: 8.4
RA: 19h53.8m Dec: +18.47
Dist: ~13,000 ly
M29 Open Cluster (2) easy*
M29 is a packet of 80 stars contained in a tiny 10’ sphere of sky. Still, this cluster is visible to the naked eye as a mag 6.6 “star” about 2 degrees south-southwest of mag 2.2 Gamma Cygni. It lies in a dense region of Milky Way that runs the length of the celestial Swan (Cygnus) - a region laced with dark lanes of interstellar dust.
Messier notes: (Observed July 29, 1764) Cluster of seven or eight very faint stars, which are below (Gamma) Cygni, and which look like a nebula in a simple three foot refractor.
NGC note: Cluster, poor and little compressed, bright, and faint stars.
Data: Messier 29 aka NGC 6913
Con: Cygnus Mag: 6.6
RA: 20h24.1m Dec: +38.30
Dist: ~5,500 ly
* Sky Tools offers an observability scale of 1 – 6, with 1 being “Obvious” and 6 being “Very Challenging”. This particular rating scale I use is based on a Celestron SCT 8 Evolution telescope at the HAS dark site on a moonless night.
Ex astris, scientia, y’all!
Field Trips and Observing Chair
Want more? Check out the HAS website under “Programs”/Messier Challenge/HAS 45