Zwicky estimated the cluster's total mass based on the motions of galaxies near its edge and compared that estimate to one based on the number of galaxies and total brightness of the cluster.

The Trumpler scheme gives a cluster a three part designation, with a Roman numeral from I-IV indicating its concentration and detachment from the surrounding star field ( from strongly to weakly concentrated ), an Arabic numeral from 1 to 3 indicating the range in brightness of members ( from small to large range ), and p, m or r to indication whether the cluster is poor, medium or rich in stars.

Because the stars in an open cluster are all at roughly the same distance from Earth, and were born at roughly the same time from the same raw material, the differences in apparent brightness among cluster members is due only to their mass.

* 1991 — Donald Gudehus discovers a serious systematic bias in certain cluster galaxy data ( surface brightness vs. radius parameter, and the method ) which affect galaxy distances and evolutionary history ; he devises a new distance indicator, the reduced galaxian radius parameter,, which is free of biases,

The constituent stars, numbering over 100 in each cluster, range widely in brightness.

* M34: This open cluster with an apparent brightness of 5. 5m lies at a distance of approximately 1, 400 ly and consists of about 100 stars that are scattered over an area larger than that of the full moon.

It is estimated that the nova reached a maximum brightness of magnitude + 9. 2, over five times brighter than the brightest ' normal ' star in the cluster.

While cataloguing open clusters, he also devised a system for their classification according to the number of stars observed within them, how concentrated these stars are in the center of the cluster and the range of their apparent brightness.

The cluster has a visual brightness of magnitude 3. 7.

The overall brightness of an extended astronomical object such as a galaxy, star cluster, or nebula, can be measured by its total magnitude, integrated magnitude or integrated visual magnitude ; a related concept is surface brightness, which specifies the brightness of a standard-sized piece of an extended object.

The total magnitude is a measure of the brightness of an extended object such as a nebula, cluster or galaxy.

The crowd consequently breaks up into temporary groups ranging in size from two to six, with a half-life for the cluster ranging from three to twenty minutes.

We know that much is made of the multiplicity and ambiguity of the identities that cluster around the key symbol of the Jew.

I think these attributes cluster, but I have no evidence.

Thus ideas like `` grace '', `` salvation '', and `` providence '' cluster together in traditional Christianity.

and about a mile to the west a cluster of at least fifty Militia were making their way in our direction.

If we cluster together, the redcoats can make an advantage out of it, but there's not a blessed thing they can do with two or three of us except chase us, and we can outrun them ''.

About 300 yards up the creek was a cluster of Mexican houses containing six rooms in the form of a square.

Yet the violent immediacy of the wallpaper strips pasted to the paper, and the only lesser immediacy of block capitals that simulate window lettering, manage somehow to push the grape cluster back into place on the picture plane so that it does not `` jump ''.

The meat wagon, therefore, was not out in front of the house any more, but the cluster of squad cars was still there and there was a cop on the door downstairs to screen any comings and goings.

You shoulder your way through the cluster of the curious and you barge up to the cop on the door.

We did 80 miles an hour across a hard dirt road to a cluster of shacks.

The camp was a cluster of aluminum bubbles, ringed with a spy web to alert the Earthmen to the approach of any being.

In the wood frog ( Rana sylvatica ), the interior of the globular egg cluster has been found to be up to 6 ° C ( 11 ° F ) warmer than its surroundings which is an advantage in its cool northern habitat.

Lungless salamanders in the family Plethodontidae are terrestrial and lay a small number of unpigmented eggs in a cluster among damp leaf litter.

The male Colostethus subpunctatus, a tiny frog, protects his egg cluster which is hidden under a stone or log.

In German, words starting with sch-( constituting the German phoneme ) would be intercalated between words with initial sca-and sci-( all incidentally loanwords ) instead of this graphic cluster appearing after the letter s, as though it were a single letter — a lexicographical policy which would be de rigueur in a dictionary of Albanian, i. e. dh -, ë -, gj -, ll -, rr -, th -, xh-and zh-( all representing phonemes and considered separate single letters ) would follow the letters d, e, g, l, n, r, t, x and z respectively.

Instead of having a pulp cavity, each tooth has a cluster of thin, upright, parallel tubes of vasodentin ( a modified form of dentine ), with individual pulp canals, held together by cementum.

To find an object, such as globular cluster NGC 6712, one does not need to look up the RA and Dec coordinates in a book, and then move the telescope to those numerical readings.

Almost all species have a tight cluster of leaves ( a rosette ), either at the base of the plant or at the end of a more-or-less woody stem ; the leaves are less often produced along the stem.

Almost all species have a tight cluster of leaves ( a rosette ) at the base of the plant or, in the tree-forming species, at the end of a woody stem.

They are herbs with corms and an inflorescence forming a cluster.

An archipelago ( ), sometimes called an island group or island chain, is a chain or cluster of islands.

Alpha decay, like other cluster decays, is fundamentally a quantum tunneling process.

Every study has found that instead of people's MBTI scores clustering around two opposite poles, such as intuition vs. sensation, with few people scoring in the middle, people's scores actually cluster around the middle of each scale in a bell curve.

Different clustering techniques make different assumptions on the structure of the data, often defined by some similarity metric and evaluated for example by internal compactness ( similarity between members of the same cluster ) and separation between different clusters.

* cluster: hierarchical clustering, vector quantization, K-means

defines actual changes in cohesive forces and their reproduction in form of kinetic or frictional forces in liquid when the clustering of the nano-particles scatter in medium for making smaller cluster or aggregates of different manometer levels.

In data mining, hierarchical clustering is a method of cluster analysis which seeks to build a hierarchy of clusters.

One way of clustering a set of data points in a metric space into two clusters is to choose the clusters in such a way as to minimize the sum of the diameters of the clusters, where the diameter of any single cluster is the largest distance between any two of its points ; this is preferable to minimizing the maximum cluster size, which may lead to very similar points being assigned to different clusters.

To test whether a given sum of diameters can be achieved without knowing the individual cluster diameters, one may try all maximal pairs of target diameters that add up to at most the given sum, representing each pair of diameters as a 2-satisfiability instance and using a 2-satisfiability algorithm to determine whether that pair can be realized by a clustering.

Cluster analysis or clustering is the task of assigning a set of objects into groups ( called clusters ) so that the objects in the same cluster are more similar ( in some sense or another ) to each other than to those in other clusters.

DeLi-Clu, Density-Link-Clustering is a cluster analysis algorithm that uses the R-tree structure for a similar kind of spatial join to efficiently compute an OPTICS clustering.

In graph theory, a clustering coefficient is a measure of degree to which nodes in a graph tend to cluster together.

The corresponding unsupervised procedure is known as clustering ( or cluster analysis ), and involves grouping data into categories based on some measure of inherent similarity ( e. g. the distance between instances, considered as vectors in a multi-dimensional vector space ).

What causes hash functions to cluster is not well understood, and it is easy to unintentionally write a hash function which causes severe clustering.

The clustering algorithms dynamically organize a given network into cluster heads and cluster members.

; wadi: a robust hetorgeneous clustering engine used to cluster geronimo, tomcat, jetty and other containers eventually.

The is built by clustering representative sequences ( the longest sequence in a cluster ) using the CD-HIT algorithm such that each cluster is composed of sequences that have at least 90 % sequence identity, to the representative sequence.

This method results in primary clustering, and as the cluster grows larger, the search for those items hashing within the cluster becomes less efficient.

In data mining, k-means clustering is a method of cluster analysis which aims to partition n observations into k clusters in which each observation belongs to the cluster with the nearest mean.

Additionally, they both use cluster centers to model the data, however k-means clustering tends to find clusters of comparable spatial extent, while the expectation-maximization mechanism allows clusters to have different shapes.

The project's main software product is Heartbeat, a GPL-licensed portable cluster management program for high-availability clustering.