astronomy

NGC 869

NGC 869 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 869 rather than just read about it. In short: NGC 869 (also known as h Persei) is an open cluster of stars located around 7,460 light years away in the constellation of Perseus. The cluster is around 14 million years old.

Key takeaways

NGC 869 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 869 to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of NGC 869 from memory before moving on to harder problems.

Reference excerpt

NGC 869 (also known as h Persei) is an open cluster of stars located around 7,460 light years away in the constellation of Perseus. The cluster is around 14 million years old. It is the west component of the Double Cluster with NGC 884. NGC 869 and 884 are often designated h and χ (chi) Persei, respectively. Some confusion surrounds what Bayer intended by these designations. It is sometimes claimed that Bayer did not resolve the pair into two patches of nebulosity, and that χ refers to the Double Cluster and h to a nearby star. Bayer's Uranometria chart for Perseus does not show them as nebulous objects, but his chart for Cassiopeia does, and they are described as Nebulosa Duplex in Schiller's Coelum Stellatum Christianum, which was assembled with Bayer's help. The clusters are both located in the Perseus OB1 association, a few hundred light years apart from each other. The clusters were first recorded by Hipparchus, thus have been known since antiquity. The Double Cluster is often photographed and observed with small telescopes. The clusters are visible with the unaided eye between the constellations of Perseus and Cassiopeia as a brighter patch in the winter Milky Way. In small telescopes, the cluster appears as an assemblage of bright stars located in a rich star field. Dominated by bright blue stars, the cluster also hosts a few orange stars.

References

External links Media related to NGC 869 at Wikimedia Commons NGC 869 at SEDS NGC 869 at Silicon Owl NGC 869 at Messier45

Illustrations

Worked examples

Example 1 — a first encounter with NGC 869

Start with the simplest possible case. Write down what NGC 869 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 869 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 869 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 869

In research: NGC 869 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 869 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 869 is common in secondary-school and first-year university syllabi. It links to neighbouring topics Astronomical objects known since antiquity, Bayer objects, Caldwell objects, so understanding it makes those chapters shorter.
In everyday life: Look for NGC 869 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 869 in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what NGC 869 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 869 out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is NGC 869 in simple terms?

NGC 869 (also known as h Persei) is an open cluster of stars located around 7,460 light years away in the constellation of Perseus. The cluster is around 14 million years old.

Why does NGC 869 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 869?

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 869.