05.06.2013 Views

The Caldwell Objects

The Caldwell Objects

The Caldwell Objects

SHOW MORE
SHOW LESS

Create successful ePaper yourself

Turn your PDF publications into a flip-book with our unique Google optimized e-Paper software.

"nebulous clusters" (Class II); and "stars accompanied<br />

by nebulosity" (Class III). Of his work<br />

Lacaille wrote: "I have found a great number of<br />

the three types of nebulosities in the southern<br />

part of the sky, but I do not flatter myself to think<br />

that I have noticed them all, especially those of<br />

the first and third types, because they can only be<br />

perceived after twilight and in the absence of the<br />

moon. However, I do hope that the list is<br />

passably complete in regard to the most<br />

remarkable of the three types."<br />

Lacaille's list of nebulae first appeared in<br />

1755, in the Memoires of the French Royal<br />

Academy of Sciences (16 years before Charles<br />

Messier published his first list of 45 objects in the<br />

same journal) and was published posthumously<br />

as a catalog in 1763. NGC 2477 is the third object<br />

in Lacaille's Class I and hence is denoted Lac 1-3.<br />

This means he did not fully resolve the cluster<br />

with his modest telescopes. He simply described<br />

NGC 2477 as a "[g]reat nebula 15[']x 20' in<br />

diameter."<br />

In the February 1960 issue of Sky & Telescope,<br />

Harvard University historian Owen Gingerich<br />

related the following report that Lacaille gave to<br />

the French Royal Academy:<br />

<strong>The</strong> so-called nebulous stars offer to the eyes of the<br />

observers a spectacle so varied<br />

that their exact and detailed description can occupy<br />

astronomers for a long time and give rise to a great<br />

number of curious reflections on the part of<br />

philosophers. As singular as those nebulae are which<br />

can be seen from Europe, those which lie in the<br />

vicinity of the south pole concede to them nothing,<br />

either in number or appearance. I am sketching out<br />

this description and list to serve as a guide for those<br />

with the equipment and leisure to study them with<br />

larger telescopes. I would have greatly desired to<br />

present something more detailed and instructive in<br />

this article, but with ordinary refractors of 15 to 18<br />

inches [in length] such as I had at the Cape of Good<br />

Hope, I had neither adequate nor convenient enough<br />

instruments for this kind of research. Those who do<br />

take the trouble to see what has occupied me during<br />

my foreign sojourn will see well enough that I did not<br />

have time to make that sort of observation.<br />

71<br />

Lacaille's work did not go unnoticed.<br />

Magnanimous Messier credited Lacaille for his<br />

discoveries in his now-famous 1771 catalog<br />

(which wasn't published until 1774).<br />

James Dunlop also observed NGC 2477 from<br />

Parramatta and included it as No. 535 in his 1827<br />

catalog, describing it as a "pretty large faint<br />

nebula, easily resolvable into small stars, or<br />

rather a cluster of very small stars, with a small<br />

faint nebula near the north preceding<br />

[northwestern] side, which is rather difficult to<br />

resolve into exceedingly small stars."<br />

Observers at tropical or southern latitudes<br />

will find NGC 2477 in a naked-eye Cygnus- or<br />

Grus-like asterism, with Canopus (Alpha<br />

Carinae) serving as the bird's nose and Zeta<br />

Puppis the tail; Tau (τ) and Sigma (σ) Puppis are<br />

the two brightest stars in the bird's long, crooked<br />

neck. Pi (π) Puppis, which is part of the nakedeye<br />

open cluster Collinder 135, marks the<br />

northern wingtip, while beautiful Gamma<br />

<strong>The</strong> <strong>Caldwell</strong> <strong>Objects</strong> 285

Hooray! Your file is uploaded and ready to be published.

Saved successfully!

Ooh no, something went wrong!