梅洛特星团

译者注：本文是Melotte星团表的出版论文，而Melotte星团表也叫富兰克林-亚当斯星图显示的星团目录。

图表板的比例尺为20毫米每度，该比例尺特别适用于星团的检查。在球状星团中，只有直径小于3'的那些很难分类，而大型的开放星团并没有因为其规模太大而失去其特征性外观。此外，由于图表板的极限星等在十六和十七之间，并且在整个天空上合理地是均匀的，因此对板块上显示的所有星团的系统分类为考虑其分布提供了非常有价值的材料。为此目的，星团被分为以下几类：

* I.中心压缩的球状星团，可以考虑以下例子：NGC 5139，Messier 13，Messier 10。
* II.具有规则，定义明确的轮廓的松散的星团，例如NGC 1245，Messier 14。
* III.松散的星团，通常只有几颗星，轮廓不规则。大多数这些都存在于银河系的较丰富部分，有时很难决定是否将其归为II类。或III。
* IV.粗星团。这些数量很少，包括昴星团，毕星团，以及上面三个类别中未包括的一些较小的组。

The majority of the clusters are comprised in the first two classes. Since it is impossible to draw a hard-and-fast line between the different classes, it has occasionally been found difficult to decide to which group a cluster should properly belong. It will be seen later, however, that this will not affect the conclusions drawn as to the distribution of star clusters in general.

大部分星团都包含在前两个类别中。由于不可能在不同的类之间划定一条硬线，因此偶尔发现很难决定一个星团应正确属于哪个组的情况。但是，稍后将看到，这一般不会影响有关星团分布的结论。

As a preliminary step the clusters belonging to the first two classes were marked on a globe. It was found that whilst clusters of Class II. are distributed in the plane of the galaxy, those belonging to Class I. are nearly all contained in one hemisphere, the pole of which is approximately R. A. 16h30m, Dec. - 58° (galactic longitude 296°, latitude - 8°). This distribution accords with that found by Mr. Hinks *(Monthly Notices,* lxxi. p. 693). It was noted, however, that there is a marked concentration of globular clusters towards a point in the galaxy about longitude 325°, and it became evident that any discussion regarding the distribution of star clusters would best be made by referring them to the galactic plane. The whole of the clusters noted have therefore been plotted, in galactic co-ordinates, on two charts. In the case of the globular clusters a stereographic projection has been employed, since it is necessary to depict rather more than one complete hemisphere. As practically all the clusters in Classes II., III., and IV. lie within 30° of the galactic plane, they have all been plotted on the same diagram on squared paper.

作为初步步骤，属于前两类的星团被标记在地球仪上。研究发现，当第二类星团分布在银河系的平面上，那些属于一类的几乎都包含在一个半球中，其极点大约为R. A. 16h30m, Dec. - 58° (galactic longitude 296°, latitude - 8°)。这一分布与Hinks发现的一致。然而，有人注意到，有一个明显的球状星团集中在银河系中一个经度325°的点上，很明显，任何关于星团分布的讨论最好是通过将它们指代到银河系平面来进行。因此，所记录的所有星团都被绘制在两张图表上，以星系坐标表示。在球状星团的情况下，使用了赤平投影，因为有必要描绘超过一个完整的半球。实际上，第二类、第三类和第四类中的所有星团都位于银河系平面的30°范围内，它们都被绘制在同一张方纸上。

Considering first the distribution of the globular clusters, Class I. The total number noted is 82. Most are to be found within latitudes ±30° and between longitudes 235° and 5°. Forty-two are within 30° of a point in the galactic plane about longitude 325°, and 19 of these are less than 5' in diameter. Considering next the distribution in latitude, 30 are within ±10°, 56 within ±20°, 63 within ±30°, and 19 beyond this limit. It will be seen that although the globular clusters are found to extend over an entire hemisphere, yet they are evidently concentrated toward a point in the galactic plane. They are distributed according to size as follows:—47 are under 5' in diameter; 22 are between 5' and 10'; 11 between 10' and 20'; and 2 exceed 20' in diameter.

首先考虑一类球状星团的分布，总共记录到82个。大多数分布在纬度±30°和235°至5°经度之间。42个在银河系平面约325°经度的30°内，其中19个直径小于5'。再考虑纬度分布，30度在±10°之内，56度在±20之内，63度在±30之内，19度在这个极限之外。可以看到，虽然球状星团被发现延伸到整个半球，但它们显然集中在银河平面的一个点上。它们按如下尺寸分布：47个直径在5'以下；22个直径在5'到10'之间；11个直径在10'到20'之间；2个直径超过20'之间。

The clusters which have been included in Classes II. and III., it will be seen from the diagram, are fairly evenly intermingled, and their distribution may therefore be considered as a whole. With two exceptions, they all lie within 30° of the galactic plane, whilst the majority are within 20°. Between longitudes 240° and 40° they form a narrow belt extending between latitudes ±10°, whilst they tend to spread out in latitude between longitudes 60° and 220°.

已列入第二类的星团。从图中可以看出，三者是相当均匀地混合在一起的，因此它们的分布可以看作是一个整体。除了两个例外，它们都位于银河平面的30°以内，而大多数都在20°以内。在240°和40°之间，它们形成一条在纬度±10°之间延伸的窄带，而它们往往在纬度60°和220°之间展开。

Only a few clusters, 14 in all, have been included under Class IV. With the exception of the large cluster in Coma Berenices, which is at latitude +85°, they are all within 30° of the galactic plane. Although no stress can be laid on it, it is curious to note that the large clusters—the Hyades, Pleiades, and Perseus cluster— fall not far from longitude 140°.

只有少数星团，总共14个，被归为第四类。除了在后发座中的大星团在纬度+85°外，它们都在银河平面的30°范围内。尽管没有压力可以施加在它上面，但很奇怪的是，大的星团，如毕星团、昴宿星团和英仙座星团，落在离经度140°不远的地方。

If the distribution of clusters as a whole be considered, it will be seen that the great majority are distributed over a zone within ±30° of the galactic plane, and that only a few, mostly of Class I., are to be found outside these limits. Further, it is to be noted that there is a distinct tendency for the globular clusters (Class I.) to crowd together about longitude 325°, and that opposite this point the clusters appear spread out over a somewhat wider range in latitude and include some of the most extended.

如果把星团的分布作为一个整体来考虑的话，就会发现绝大多数星团分布在银河平面±30°范围内的一个区域上，只有少数星团（主要是一级星团）在这些界限之外。此外，值得注意的是，球状星团（I类）在经度325°左右聚集在一起的趋势是明显的，而在这一点的对面，星团在纬度上似乎分布得更广一些，包括一些最广泛的星团。

The list of clusters included in the catalogue has been compared with those to be found in Harvard Annals, vol. lx., No. 8 (Catalogue of Bright Clusters and Nebulae —BAILEY). Sixty-six clusters catalogued in the N.G.C. and noted by BAILEY are not included in the present catalogue. Most of these, 53 in number, are in the Magellanic clouds. These have all been examined and do not appear as clusters on the Franklin-Adams Plates. N.G.C. 371 is the only cluster (classed as a globular cluster) which falls in either of the two Magellanic clouds. It is not far from N.G.C. 104 and 362, also globular clusters, and it may possibly be unconnected with the cloud itself and merely be seen in the same direction.

目录中的星团列表与哈佛年鉴第十卷第八期（BAILEY明亮星团和星云目录）中的星团列表进行了比较。在N.G.C.编目并由贝利指出的66个星团不包括在本目录中。其中大多数，53个，在麦哲伦云中。这些都已经过检查，并没有出现在富兰克林亚当斯板块星团。N. G.C.371是唯一落在两个麦哲伦云中的星团（被归类为球状星团）。它离N.G.C.104和362也不远，也是球状星团，它可能与云本身没有联系，只是在同一方向上被看到。

The reasons for omitting the remaining 13 clusters will be seen from the following descriptions attached to each:

省略其余13个星团的原因将从每个星团所附的以下说明中看出：

Nine clusters have been included which do not appear either in the N.G.C. or in BAILEY’S Catalogue.

The following clusters, classed as “globular” in the N.G.C., have not been identified :

已经包括了九个星团，它们既没有出现在N.G.C.中，也没有出现在贝利的目录中。

在N.G.C.中被归类为“球状”的下列星团尚未确定：

Of these Nos. 628, 1387, 6221, and 6412 are nebulae; and 18 are in the Magellanic clouds. Numbers 376 (in the small Magellanic cloud), 1512, and 2090 are noted as not being globular clusters in the list of corrections at the end of the Second Index Catalogue. Six clusters noted in Lick Observatory Bulletin, No. 219 (Descriptions of 132 Nebulae and Clusters photographed with the Crossley Reflector), are not included in the catalogue. Their appearance on the Franklin-Adams Chart Plates is described in the following table

其中Nos. 628, 1387, 6221, and 6412是星云；编号376（在小麦哲伦云中）、1512和2090在第二个索引目录末尾的更正列表中被指出不是球状星团。

在利克天文台第219号公告中指出的六个星团（用Crossley反射镜拍摄的132个星云和星团的描述）不在目录中。它们在富兰克林亚当斯图表板上的外观如下表所示

In the catalogue which follows the R.A. and Dec. of the clusters are taken from DREYER’S New General Catalogue, etc. (Memoirs, R.A.S., vol. xlix., part 1), from the Index Catalogue and Second Index Catalogue by the same author (Memoirs, R.A.S., vols. li., lix.), and from BAILEY’S Catalogue of Bright Clusters and Nebulae (Harvard Annals, vol. lx., No. 8). References to these catalogues will be found in the notes on the clusters. In the cases of those clusters which have not been identified in the above catalogues their positions were obtained from the plates. Columns 5 and 6 give the galactic longitudes and latitudes, the adopted position of the pole of the Milky Way being R.A. i2h4im, Dec.4-270 21' (Uran. Arg., p. 371). Column 7 gives the diameter of the cluster, and column 8 the class to which each has been assigned. The description, column 9, has been made as brief as possible.

Plate I. shows the galactic distribution of the globular cluster (Class I.), dots of different sizes being used according to the observed diameters. Plate II. shows the galactic distribution of the clusters belonging to Classes II., III., and IV. Class [I. are indicated by dots, varying in size according to the diameter, Class III. by crosses, and Class IV. by circles.

The large cluster in Coma Berenices, No. 111 in the catalogue, has been omitted since, being at galactic latitude + 85°, it falls outside the diagram. N.G.C. 6539, No. 190, has also been omitted, as it is doubtful whether it should be classed as a globular cluster.

在继R.A.和Dec.之后的目录中，星团是从DREYER的新总目录等（回忆录，R.A.S.，vol.xlix.，part 1）中获取的，来自同一作者的索引目录和第二索引目录（回忆录，R.A.S.，vols）。以及贝利的明亮星团和星云目录（哈佛年鉴，第10卷，第8期）。这些目录的参考资料将在星团的注释中找到。对于上述目录中未确定的星团，它们的位置是从板块上获得的。第5列和第6列给出了银河系的经度和纬度，银河系的极点采用的位置是R.A.12h41m Dec.+27°21'（Uran. Arg.第371页）。第7列给出星团的直径，第8列给出每个星团被分配到的类。第9栏的说明尽可能简短。

板块一显示了球状星团（一类）的银河分布，根据观察到的直径使用了不同大小的点。板块二。显示了属于第二类、第三类和第四类星团的银河系分布。第一类星团用圆点表示，根据直径大小而变化，第三类星团用十字表示，第四类星团用圆圈表示。

目录中的第111号，处于后发座的大星团被忽略了，因为它位于银河纬度+85°处，落在了图表之外。N.G.C.6539，第190号，也被省略了，因为它是否应该被归类为球状星团是个疑问。

译者注：奇怪的是，Melotte目录并未收录M18和M29。