astronomy

NGC 4123

NGC 4123 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 4123 rather than just read about it. In short: NGC 4123 is a modest-sized, strongly-barred spiral galaxy located 75 million light-years away in the equatorial constellation of Virgo. It was discovered February 25, 1784 by William Herschel.

Key takeaways

NGC 4123 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 4123 to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of NGC 4123 from memory before moving on to harder problems.

Reference excerpt

NGC 4123 is a modest-sized, strongly-barred spiral galaxy located 75 million light-years away in the equatorial constellation of Virgo. It was discovered February 25, 1784 by William Herschel. This is a member of the Virgo Cluster, and it belongs to a group of three galaxies. A companion galaxy, NGC 4116, lies at an angular separation of 14′ to the southwest. There is no indication of an interaction between the two galaxies. The third member of the group is NGC 4179.

The morphological classification of NGC 4123 is SBx(rs)ab, which indicates this is a spiral galaxy with a central X-shaped bar (SBx) encircled by an incomplete ring structure (rs) and moderate to tightly wound spiral arms (ab). The plane of the galaxy is inclined at an angle of 46.9° to the line of sight from the Earth. It lacks a large spheroidal bulge at the core, showing only a luminous point-like source. Blue knots in the outer spiral arms indicate that star formation is ongoing. The galaxy has a stellar mass of 1.95×1010 M☉ with a star formation rate of 3.429±3.281 M☉·yr−1. The atomic gas in the galaxy has a mass of 1.06×1010 M☉. Radio emission has been detected from an HII nucleus, which is consistent with it having a weak active galactic nucleus. If there is a supermassive black hole at the core, it has an estimated mass of 107 M☉.

References

Further reading Weiner, B. J.; et al. (1996), Buta, R.; et al. (eds.), "Fabry-Perot Observations and Hydrodynamical Simulations of the Barred Spiral NGC 4123", Barred galaxies; Proceedings of a conference held at the University of Alabama; Tuscaloosa; Alabama; 30 May - 3 June 1995, Astronomical Society of the Pacific Conference Series, vol. 91, San Francisco: Astronomical Society of the Pacific, p. 489, Bibcode:1996ASPC...91..489W.

Illustrations

Worked examples

Example 1 — a first encounter with NGC 4123

Start with the simplest possible case. Write down what NGC 4123 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 4123 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 4123 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 4123

In research: NGC 4123 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 4123 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 4123 is common in secondary-school and first-year university syllabi. It links to neighbouring topics Astronomical objects discovered in 1784, Barred spiral galaxies, Discoveries by William Herschel, so understanding it makes those chapters shorter.
In everyday life: Look for NGC 4123 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 4123 in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what NGC 4123 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 4123 out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is NGC 4123 in simple terms?

NGC 4123 is a modest-sized, strongly-barred spiral galaxy located 75 million light-years away in the equatorial constellation of Virgo. It was discovered February 25, 1784 by William Herschel.

Why does NGC 4123 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 4123?

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 4123.