Definitions Astro "Messier Objects"

Nick Theodorakis wrote:
It looks like he was "padding" his list in the M30's to M40's -- lots
of open clusters there.

I have heard that the last four items or so (Orion Nebula, Beehive, and
Pleiades) *are* padding, but the previous ones are not. After all, just
because something is an open cluster does not mean that it doesn't appear
nebulous to a clearly suboptimal telescope. Consider M37 or M67.

For some reason, people seem to think that he wanted 45 items for his
list. I'm not sure why 45 is such a wonderful number--seems to me, I'd
have just picked out another 5 (NGC 869/884, for instance) to pad it up
to 50.

Brian Tung
The Astronomy Corner at http://astro.isi.edu/
Unofficial C5+ Home Page at http://astro.isi.edu/c5plus/
The PleiadAtlas Home Page at http://astro.isi.edu/pleiadatlas/
My Own Personal FAQ (SAA) at http://astro.isi.edu/reference/faq.txt

Nick Theodorakis wrote:
[snip]
How did M45 (or even M44) get on the list?

It looks like he was "padding" his list in the M30's to M40's
-- lots of open clusters there.

I don't think you can make a case for so many objects being "padding." However,
I do believe Messier added M42 through M45 to fill out his first catalog.

Charles Messier encountered the Crab nebula in 1758 while observing a comet. It
wasn't until 1760, two years after this observation, that Messier observed the
globular cluster that would become M2. 1760 was also the year Messier
discovered his first comet.

Over the next decade, Messier established himself as the greatest comet hunter
in Europe. His election to the Royal Society of London in 1764, and to the
Berlin Academy and the Academy of St. Petersburg in 1766 all occurred after
comet discoveries.

However, the most respected scientific body in Europe, the French Academy of
Sciences, would not have their countryman. The Academy first passed on Messier
in 1764 after his third comet discovery. I suspect it's no coincidence that
Messier began cataloging non-cometary objects with great enthusiasm in 1764.
Objects 3 through 40 were observed and noted by the Frenchman that year, alone.
He added M41 the following year but nothing more until 1769.

The night of March 4, 1769, Messier determined positions for objects 42 through
45. These were the Orion nebula, the reflection nebula just to the north of
M42, the Beehive cluster in Cancer and the Pleiades in Taurus. Three of the
four were quite well known and visible to the unaided eye. They were also the
last objects in the first Messier catalog. On August 8, 1769, Messier
discovered his fifth comet.

The years 1770 and 1771 brought three more comets. In January 1771, Messier
independently discovered the Great Comet of 1770 (1770 II). The following
month, he presented his catalog to the French Academy on the ocassion of his
election to that august body.

Viewed in this context, I believe Messier was an early case of publish or
perish syndrome. Why did he wait so many years before adding objects 42 through
45 to his catalog? The most plausible explanation is that all were well known
objects and very unlikely to be mistaken as comets. However, believing that the
French Academy was steadfast in their reluctance to elect him, Messier added
these objects to fill out the catalog he hoped would tip the scales in his
favor.

Regards,



Bill Ferris
"Cosmic Voyage: The Online Resource for Amateur Astronomers"
URL: http://www.cosmic-voyage.net
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