astronomy

NGC 3423

NGC 3423 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 3423 rather than just read about it. In short: NGC 3423 is a spiral galaxy in the constellation Sextans. The galaxy lies about 45 million light years away from Earth, which means, given its apparent dimensions, that NGC 3423 is approximately 50,000 light years across.

Key takeaways

NGC 3423 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 3423 to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of NGC 3423 from memory before moving on to harder problems.

Reference excerpt

NGC 3423 is a spiral galaxy in the constellation Sextans. The galaxy lies about 45 million light years away from Earth, which means, given its apparent dimensions, that NGC 3423 is approximately 50,000 light years across. It was discovered by William Herschel on February 23, 1784.

NGC 3423 is an unbarred galaxy seen nearly face-on. The galaxy has a low-surface-brightness disk. The galaxy has multiple spiral arms, at least six, with numerous HII regions all over the disk. The largest of them are about 2 arcseconds across. H-alpha emission is stronger at inner part of the disk. The star formation rate is estimated to be 0.7 M☉ per year. NGC 3423 is the foremost galaxy of the NGC 3423 Group, which also includes MRK 1271. Other nearby galaxies include NGC 3365, NGC 3495, and NGC 3521. During the March 2026 lunar eclipse, a total lunar eclipse, it was occulted by the Moon over North America.

Supernova and luminous blue variable One supernova and one luminous blue variable have been observed in NGC 3423.

SN 2009ls was discovered on 23 November 2009 by Koichi Nishiyama and Fujio Kabashima at an apparent magnitude of 15.3. Its spectrum revealed it was a young Type II supernova. AT 2019ahd was discovered by ATLAS on 29 January 2019. It was identified as a luminous blue variable in outburst.

References

External links

NGC 3423 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 3423

Start with the simplest possible case. Write down what NGC 3423 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 3423 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 3423 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 3423

In research: NGC 3423 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 3423 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 3423 is common in secondary-school and first-year university syllabi. It links to neighbouring topics Astronomical objects discovered in 1784, Discoveries by William Herschel, MCG objects, so understanding it makes those chapters shorter.
In everyday life: Look for NGC 3423 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 3423 in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what NGC 3423 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 3423 out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is NGC 3423 in simple terms?

Why does NGC 3423 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 3423?

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 3423.