astronomy

NGC 1643

NGC 1643 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 1643 rather than just read about it. In short: NGC 1643 is a peculiar barred spiral galaxy in the constellation of Eridanus. Its velocity with respect to the cosmic microwave background is 4,834±4 km/s, which corresponds to a Hubble distance of 232.5 ± 16.3 Mly (71.30 ± 4.99 Mpc).

Key takeaways

NGC 1643 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 1643 to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of NGC 1643 from memory before moving on to harder problems.

Reference excerpt

NGC 1643 is a peculiar barred spiral galaxy in the constellation of Eridanus. Its velocity with respect to the cosmic microwave background is 4,834±4 km/s, which corresponds to a Hubble distance of 232.5 ± 16.3 Mly (71.30 ± 4.99 Mpc). It was discovered by German-British astronomer William Herschel on 28 November 1786.

Supernovae Two supernovae have been observed in NGC 1643:

SN 1995G (Type IIn, mag. 15.5) was discovered by Robert Evans, J. Shobbrook, and S. Beaman, on 23 February 1995. SN 1999et (Type II, mag. 17.6) was discovered by E. Cappellaro on 4 November 1999.

See also List of NGC objects (1001–2000)

References

External links Media related to NGC 1643 at Wikimedia Commons NGC 1643 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 1643

Start with the simplest possible case. Write down what NGC 1643 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 1643 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 1643 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 1643

In research: NGC 1643 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 1643 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 1643 is common in secondary-school and first-year university syllabi. It links to neighbouring topics Astronomical objects discovered in 1877, Barred spiral galaxies, Discoveries by Wilhelm Tempel, so understanding it makes those chapters shorter.
In everyday life: Look for NGC 1643 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 1643 in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what NGC 1643 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 1643 out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is NGC 1643 in simple terms?

Why does NGC 1643 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 1643?

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 1643.