astronomy

List of galaxy groups and clusters

List of galaxy groups and clusters is a astronomy topic covered in the lgStudy science library. This page brings together a partial reference excerpt, illustrations, worked examples, real-world applications and a short study plan, so you can understand List of galaxy groups and clusters rather than just read about it. In short: This article lists some galaxy groups and galaxy clusters. Defining the limits of galaxy clusters is imprecise as many clusters are still forming.

Key takeaways

List of galaxy groups and clusters belongs to astronomy; place it in that map before memorising details.
Learn the definition first, then one example that makes the definition concrete.
Connect List of galaxy groups and clusters to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of List of galaxy groups and clusters from memory before moving on to harder problems.

Reference excerpt

This article lists some galaxy groups and galaxy clusters. Defining the limits of galaxy clusters is imprecise as many clusters are still forming. In particular, clusters close to the Milky Way tend to be classified as galaxy clusters even when they are much smaller than more distant clusters.

Clusters exhibiting strong evidence of dark matter Some clusters exhibiting strong evidence of dark matter.

Named groups and clusters This is a list of galaxy groups and clusters that are well known by something other than an entry in a catalog or list, or a set of coordinates, or a systematic designation.

Clusters

Groups

The major nearby groups and clusters are generally named after the constellation they lie in. Many groups are named after the leading galaxy in the group. This represents an ad hoc systematic naming system.

Groups and clusters visible to the unaided eye The Local Group contains the largest number of visible galaxies with the naked eye. However, its galaxies are not visually grouped together in the sky, except for the two Magellanic Clouds. The IC342/Maffei Group, the nearest galaxy group, would be visible by the naked eye if it were not obscured by the stars and dust clouds in the Milky Way's spiral arms.

No galaxy cluster is visible to the unaided eye.

Firsts

Extremes

Closest groups

Closest clusters

Farthest clusters

In 2003 RDCS 1252-29 (RDCS1252.9–2927) at z=1.237, was found to be the most distant rich cluster, which lasted until 2005. In 2000, a cluster was announced in the field of quasar QSO 1213-0017 at z=1.31 (the quasar lies at z=2.69) In 1999, cluster RDCS J0849+4452 (RX J0849+4452, RXJ0848.9+4452) was found at z=1.261 In 1995 and 2001, the cluster around 3C 294 was announced, at z=1.786 In 1992, observations of the field of cluster Cl 0939+4713 found what appears to be a background cluster near a quasar, also in the background. The quasar was measured at z=2.055 and it was assumed that the cluster would be as well. In 1975, 3C 123 and its galaxy cluster was incorrectly determined to lie at z=0.637 (actually z=0.218) In 1958, cluster Cl 0024+1654 and Cl 1447+2619 were estimated to have redshifts of z=0.29 and z=0.35 respectively. However, they were not spectroscopically determined.

Farthest protoclusters

In 2002, a very large, very rich protocluster, or the most distant protosupercluster was found in the field of galaxy cluster MS 1512+36, around the gravitationally lensed galaxy MS 1512-cB58, at z=2.724.

False clusters Sometimes clusters are put forward that are not genuine clusters or superclusters. Through the researching of member positions, distances, peculiar velocities, and binding mass, former clusters are sometimes found to be the product of a chance line-of-sight superposition.

Illustrations

Worked examples

Example 1 — a first encounter with List of galaxy groups and clusters

Start with the simplest possible case. Write down what List of galaxy groups and clusters claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In astronomy, the smallest case is usually a single object, a single equation or a single measurement. Check that every symbol or term in your sentence has a meaning in that case.

Example 2 — changing one variable

Take the situation from Example 1 and change exactly one quantity: double it, halve it, or set it to zero. Predict what should happen to List of galaxy groups and clusters before you calculate. Comparing your prediction with the result is the fastest way to find out whether you understand the idea or only the words.

Example 3 — an exam-style question

Typical questions about List of galaxy groups and clusters ask you to (a) state it precisely, (b) apply it to given data, and (c) explain a limitation. Practise writing all three answers in under five minutes; the third part is what separates a full-mark answer from an average one.

Applications of List of galaxy groups and clusters

In research: List of galaxy groups and clusters appears in astronomy research whenever the underlying quantities have to be modelled precisely. Papers usually cite it as a starting assumption and then explore where it breaks down.
In technology and industry: Engineering practice reuses List of galaxy groups and clusters in design rules, simulations and safety margins. Knowing the idea lets you read a specification sheet and understand why the numbers look the way they do.
In the classroom: List of galaxy groups and clusters is common in secondary-school and first-year university syllabi. It links to neighbouring topics Galaxy clusters, Lists of clusters, so understanding it makes those chapters shorter.
In everyday life: Look for List of galaxy groups and clusters outside the textbook — in sport, cooking, traffic, electronics or the sky above you. An example you found yourself is remembered far longer than one you were given.

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How to study List of galaxy groups and clusters in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what List of galaxy groups and clusters means in your own words.
Compare your version with the excerpt and mark what you missed.
Work through the three examples above with pen and paper.
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Frequently asked questions

What is List of galaxy groups and clusters in simple terms?

This article lists some galaxy groups and galaxy clusters. Defining the limits of galaxy clusters is imprecise as many clusters are still forming.

Why does List of galaxy groups and clusters matter?

Because it connects several astronomy ideas at once: it gives you a definition you can apply, a quantity you can calculate, and a way to check whether a result is plausible.

How should I study List of galaxy groups and clusters?

Read the excerpt, restate it from memory, then work through the examples and applications listed on this page. The five-step study plan above takes about twenty minutes.

What does this page cover?

It gives you a compact reference excerpt plus original lgStudy explanations, examples, applications and study material on List of galaxy groups and clusters.