astronomy

NGC 797

NGC 797 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 797 rather than just read about it. In short: NGC 797 (also known as NGC 797 NED02) is a barred spiral galaxy in the constellation of Andromeda. Its velocity with respect to the cosmic microwave background is 5,414±17 km/s, which corresponds to a Hubble distance of 260.4 ± 18.3 Mly (79.85 ± 5.60 Mpc).

Key takeaways

NGC 797 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 797 to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of NGC 797 from memory before moving on to harder problems.

Reference excerpt

NGC 797 (also known as NGC 797 NED02) is a barred spiral galaxy in the constellation of Andromeda. Its velocity with respect to the cosmic microwave background is 5,414±17 km/s, which corresponds to a Hubble distance of 260.4 ± 18.3 Mly (79.85 ± 5.60 Mpc). However, three non-redshift measurements give a much farther mean distance of 369.64 ± 4.35 Mly (113.333 ± 1.333 Mpc). It was discovered by German-British astronomer William Herschel on 21 September 1786. In 1971, Fritz Zwicky and his daughter, Margrit A. Zwicky, published Catalogue of Selected Compact Galaxies and of Post-Eruptive Galaxies, which showed that NGC 797 has an elliptical compact companion galaxy at the tip of its southwest spiral arm, and catalogued the galaxy pair as CGPG 0200.4+3753. The companion galaxy is catalogued as NGC 0797 NED01 and PGC 212899, among other designations. NGC 797 and NGC 801 form a galaxy pair, and the distance between the two is about 150 kiloparsecs.

Supernova One supernova has been observed in NGC 797:

SN 2025pel (Type Ia, mag. 18.41) was discovered by GOTO on 17 June 2025.

Illustrations

Worked examples

Example 1 — a first encounter with NGC 797

Start with the simplest possible case. Write down what NGC 797 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 797 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 797 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 797

In research: NGC 797 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 797 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 797 is common in secondary-school and first-year university syllabi. It links to neighbouring topics Andromeda (constellation), Astronomical objects discovered in 1786, Barred spiral galaxies, so understanding it makes those chapters shorter.
In everyday life: Look for NGC 797 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 797 in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what NGC 797 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 797 out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is NGC 797 in simple terms?

Why does NGC 797 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 797?

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 797.