astronomy

NGC 3994

NGC 3994 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 3994 rather than just read about it. In short: NGC 3994 is an unbarred spiral galaxy in the constellation Ursa Major. The galaxy lies about 160 million light years away from Earth, which means, given its apparent dimensions, that NGC 3994 is approximately 70,000 light years across.

Key takeaways

NGC 3994 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 3994 to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of NGC 3994 from memory before moving on to harder problems.

Reference excerpt

NGC 3994 is an unbarred spiral galaxy in the constellation Ursa Major. The galaxy lies about 160 million light years away from Earth, which means, given its apparent dimensions, that NGC 3994 is approximately 70,000 light years across. It was discovered by Heinrich d'Arrest on April 6, 1864. NGC 3994 forms a triplet of galaxies with NGC 3995, which lies 1.9 arcminutes, and NGC 3991, which lies 3.7 arcminutes away. The triplet has been included in Halton Arp's Atlas of Peculiar Galaxies as Arp 313. Both NGC 3995 and NGC 3991 have a disturbed appearance while NGC 3994 does not. The triplet is part of the NGC 3966 Group or LGG 259. Other members include NGC 3966, NGC 3935, NGC 3986, IC 2973, UGC 6892, IC 2978, and IC 2979. The nucleus of the galaxy has been found to be active, and based on its spectral lines it is a composite object with LINER and HII region characteristics. The nucleus lacks central ultraviolet emission when observed by the Hubble Space Telescope. Star formation knots are visible along the spiral arms, most of them with ages less than 20 million years, with no correlation between location and age. The star formation rate of NGC 3995 is estimated to be 2.9±0.6 M☉ per year, with higher rates observed near the centre of the galaxy.

References

External links

NGC 3994 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 3994

Start with the simplest possible case. Write down what NGC 3994 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 3994 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 3994 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 3994

In research: NGC 3994 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 3994 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 3994 is common in secondary-school and first-year university syllabi. It links to neighbouring topics Arp objects, Astronomical objects discovered in 1864, Discoveries by Heinrich Louis d'Arrest, so understanding it makes those chapters shorter.
In everyday life: Look for NGC 3994 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 3994 in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what NGC 3994 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 3994 out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is NGC 3994 in simple terms?

Why does NGC 3994 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 3994?

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 3994.