astronomy

NGC 309

NGC 309 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 309 rather than just read about it. In short: NGC 309 is a spiral galaxy in the constellation Cetus. Its velocity with respect to the cosmic microwave background is 5343 ± 22 km/s, which corresponds to a Hubble distance of 257.0 ± 18.0 Mly (78.81 ± 5.53 Mpc).

Key takeaways

NGC 309 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 309 to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of NGC 309 from memory before moving on to harder problems.

Reference excerpt

NGC 309 is a spiral galaxy in the constellation Cetus. Its velocity with respect to the cosmic microwave background is 5343 ± 22 km/s, which corresponds to a Hubble distance of 257.0 ± 18.0 Mly (78.81 ± 5.53 Mpc). However, nine non-redshift measurements give a much closer distance of 87.99 ± 10.45 Mly (26.978 ± 3.205 Mpc). It was discovered in 1876 by Wilhelm Tempel. NGC 309 and NGC 309A are listed together as Holm 27 in Erik Holmberg's A Study of Double and Multiple Galaxies Together with Inquiries into some General Metagalactic Problems, published in 1937.

Supernovae Five supernovae have been observed in NGC 309.

Illustrations

Worked examples

Example 1 — a first encounter with NGC 309

Start with the simplest possible case. Write down what NGC 309 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 309 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 309 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 309

In research: NGC 309 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 309 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 309 is common in secondary-school and first-year university syllabi. It links to neighbouring topics Astronomical objects discovered in 1876, Cetus (constellation), Discoveries by Wilhelm Tempel, so understanding it makes those chapters shorter.
In everyday life: Look for NGC 309 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 309 in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what NGC 309 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 309 out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is NGC 309 in simple terms?

Why does NGC 309 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 309?

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 309.