astronomy

NGC 2939

NGC 2939 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 2939 rather than just read about it. In short: NGC 2939 is a spiral galaxy in the constellation of Leo. Its velocity with respect to the cosmic microwave background is 3,665±23 km/s, which corresponds to a Hubble distance of 176.3 ± 12.4 Mly (54.05 ± 3.80 Mpc).

Key takeaways

NGC 2939 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 2939 to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of NGC 2939 from memory before moving on to harder problems.

Reference excerpt

NGC 2939 is a spiral galaxy in the constellation of Leo. Its velocity with respect to the cosmic microwave background is 3,665±23 km/s, which corresponds to a Hubble distance of 176.3 ± 12.4 Mly (54.05 ± 3.80 Mpc). However, 13 non-redshift measurements give a closer mean distance of 149.30 ± 5.20 Mly (45.777 ± 1.594 Mpc). It was discovered by German-British astronomer William Herschel on 18 January 1784. NGC 2939 is a radio galaxy, i.e. it has giant regions of radio emission extending well beyond its visible structure.

NGC 2911 group NGC 2939 is a member of the NGC 2911 group (also known as LGG 177). This group contains 7 galaxies, including NGC 2911, NGC 2913, NGC 2914, UGC 5189, UGC 5216, and PGC 27167.

Supernovae Two supernovae have been observed in NGC 2939:

SN 2009ao (Type II-P, mag. 16.3) was discovered by The CHilean Automatic Supernova sEarch (CHASE) on 4 March 2009. SN 2011cf (Type II, mag. 18.2) was discovered by the Lick Observatory Supernova Search (LOSS) on 28 April 2011.

See also List of NGC objects (2001–3000)

References

External links Media related to NGC 2939 at Wikimedia Commons NGC 2939 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 2939

Start with the simplest possible case. Write down what NGC 2939 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 2939 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 2939 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 2939

In research: NGC 2939 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 2939 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 2939 is common in secondary-school and first-year university syllabi. It links to neighbouring topics Astronomical objects discovered in 1784, Discoveries by William Herschel, IRAS catalogue objects, so understanding it makes those chapters shorter.
In everyday life: Look for NGC 2939 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 2939 in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what NGC 2939 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 2939 out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is NGC 2939 in simple terms?

Why does NGC 2939 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 2939?

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 2939.