The Missing Messier Objects -

The Missing Messier Objects

Unlike his contemporary and earlier colleagues,

Charles Messier was such a

careful observer that all objects in

his catalog (possibly with the exception

of M102) actually exist and could be identified with

real celestial objects. However, he was not always an error-free recorder and

data-reducer, making some few mistakes which have hidden 4 objects for more

than a century, so that they were missed.

The missing objects are

M47,

M48,

M91, and

M102.

M47 was missed because Messier did a sign

error during the reduction of positional data. He computed the position of

this cluster from the differences to the star 2 Puppis (2 Navis in Messier’s

time), but mistook the sign of the right ascension difference. This fact was

recognized by T.F. Morris of the RAS of Canada in 1959, after Oswald Thomas

had identified it correctly as NGC 2422 in his 1934 book Astronomie.

Previously, John Herschel had given the wrong position a number in his

General Catalogue, and following him, J.L.E. Dreyer a NGC number, NGC 2478,

although at that position there’s no object at all.

M48 is not so obvious, but as (the same

astronomer) T.F. Morris pointed out in 1959, the only object matching Messier’s

description in this celestial area is NGC 2548, which is now generally

recognized as M48. It lies at the same right ascension, but almost exactly 5

degrees south of Messier’s position. The reasons for this error will probably

remain obscure unless Messier’s lost observing books of this period should

come to light one day.

M91 was much more difficult to reconstruct;

finally, Messier had measured the position of this galaxy from the previously

discovered M89, but thought he had used M58, as the amateur astronomer

William C. Williams of Texas had found out and thus identified M91 with

NGC 4548, now generally accepted and quite safe. Previously, it had been

assumed that M91 might be the 12 mag galaxy NGC 4571, the nearest to

Messier’s position – unlikely but not totally impossible. Many sources also

held the version that it was actually a comet that fooled Messier – even more

unlikely with regard to the fact that Messier was the comet specialist,

and Owen Gingerich had brought up the hypothesis that it might be a duplicate

observation of M58.

M102 finally could not be cleared up with

certainty up to now. At last, there are still two possibilities open:

It may be a duplication of M101, as its discoverer

Pierre Mechain believed when he wrote a letter to Bernoulli in Germany two

years later, but on the other hand, its description in Messier’s catalog

(which was actually Mechain’s description) matches well with

NGC 5866.

Moreover it may be that Charles Messier has observed this object when

measuring the position of M102 which he wrote by hand into his personal copy

of the catalog, but did a data reduction error again, plotting it exactly 5

degrees west (preceding) of its true position in right ascension.

The present author has discussed this topic and

thinks it depends on taste to believe which was erroneous: the observation or

the letter, or if Messier’s possible observation justifies the designation

`M102′ for this object.

To summarize: The four missing Messier objects were probably missed because of

errata of Messier in data reduction, in detail one sign error (for M47), one

mistaken comparison object (for M91) and one or, probably, two “grid” errors,

i.e. positions which are exactly 5 degrees off (for M48 in declination, for

the M102 candidate NGC 5866 in right ascension), which is the grid tick width

in the charts he used

(see e.g. this example)

and can thus be explained by wrong looks or labels.

Last Modification: 25 Jan 1998, 14:50 MET