astronomy

NGC 457

NGC 457 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 NGC 457 rather than just read about it. In short: NGC 457 is an open cluster of stars in the northern constellation of Cassiopeia. Alternatively, it is designated Caldwell 13, and known as the Dragonfly Cluster, E.T.

Key takeaways

NGC 457 belongs to astronomy; place it in that map before memorising details.
Learn the definition first, then one example that makes the definition concrete.
Connect NGC 457 to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of NGC 457 from memory before moving on to harder problems.

Reference excerpt

NGC 457 is an open cluster of stars in the northern constellation of Cassiopeia. Alternatively, it is designated Caldwell 13, and known as the Dragonfly Cluster, E.T. Cluster, Owl Cluster, Kachina Doll Cluster or Phi Cassiopeiae Cluster. It was discovered by German-British astronomer William Herschel on August 18, 1780, with a 6.2 inch reflector telescope, and catalogued as VII 42. This is an easy target for amateur astronomers, and can be seen even with small telescopes in light-polluted skies.

Characteristics It lies over 7,900 light years away from the Sun. It has an estimated age of 21 million years. The cluster is sometimes referred by amateur astronomers as the Owl Cluster or the E.T. Cluster (due to its resemblance to the movie character). Two bright stars Phi Cassiopeiae (magnitude 5 and spectral type F0) and HD 7902 (magnitude 7) can be imagined as eyes. It is not yet clear if Phi Cassiopeiae is a member of the cluster, and if it is, then it would be one of the brightest stars known, surpassing Rigel in luminosity. For comparison, the Sun at the same distance as Phi Cassiopeiae would shine at just 17.3 magnitude. The next brightest star is the red supergiant variable star V466 Cassiopeiae. The cluster features a rich field of about 150 stars of magnitude 9-13. About 60 stars have been identified as true members of the cluster.

Gallery

References

External links Media related to NGC 457 at Wikimedia Commons "NGC 457 on SEDS".

NGC 457 on WikiSky: DSS2, SDSS, GALEX, IRAS, Hydrogen α, X-Ray, Astrophoto, Sky Map, Articles and images

Illustrations

Worked examples

Example 1 — a first encounter with NGC 457

Start with the simplest possible case. Write down what NGC 457 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 NGC 457 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 NGC 457 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 NGC 457

In research: NGC 457 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 NGC 457 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: NGC 457 is common in secondary-school and first-year university syllabi. It links to neighbouring topics Astronomical objects discovered in 1787, Caldwell objects, Cassiopeia (constellation), so understanding it makes those chapters shorter.
In everyday life: Look for NGC 457 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 NGC 457 in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what NGC 457 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.
Explain NGC 457 out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is NGC 457 in simple terms?

NGC 457 is an open cluster of stars in the northern constellation of Cassiopeia. Alternatively, it is designated Caldwell 13, and known as the Dragonfly Cluster, E.T.

Why does NGC 457 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 NGC 457?

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 NGC 457.