astronomy

NGC 3923

NGC 3923 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 3923 rather than just read about it. In short: NGC 3923 is an elliptical galaxy located in the constellation Hydra. It is located at a distance of about 90 million light years from Earth, which, given its apparent dimensions, means that NGC 3923 is about 155,000 light years across.

Key takeaways

NGC 3923 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 3923 to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of NGC 3923 from memory before moving on to harder problems.

Reference excerpt

NGC 3923 is an elliptical galaxy located in the constellation Hydra. It is located at a distance of about 90 million light years from Earth, which, given its apparent dimensions, means that NGC 3923 is about 155,000 light years across. NGC 3923 is an example of a shell galaxy where the stars in its halo are arranged in layers. It has more than twenty shells. It was discovered by William Herschel on March 7, 1791.

Characteristics

NGC 3923 is an example of a shell galaxy where the stars in its halo are arranged in layers. NGC 3923 has up to 42 shells, the highest number among all shell galaxies, and its shells are much more subtle than those of other shell galaxies. The shells of this galaxy are also symmetrical, while other shell galaxies are more skewed and asymmetrical. Concentric shells of stars enclosing a galaxy are quite common and are observed in many elliptical galaxies. In fact, every tenth elliptical galaxy exhibits this onion-like structure, which has never been observed in spiral galaxies. The shell-like structures are thought to develop as a consequence of galactic cannibalism, when a larger galaxy ingests a smaller companion. As the two centers approach, they initially oscillate about a common center, and this oscillation ripples outwards forming the shells of stars just as ripples on a pond spread when the surface is disturbed. Deep imaging also detected a stream extending from the core of NGC 3923 and a small elliptical galaxy on its axis, which is a probable progenitor of some of the shells. Another stream lies south of the core of NGC 3923, and a hook like structure lies at the northwest. Based on the velocity dispersion of the globular clusters of NGC 3923 the mass of the supermassive black hole of the galaxy was estimated to be (5.3±2.5)×108 M☉.

Supernova One supernova has been observed in NGC 3923. SN 2018aoz (Type Ia, mag. 15.1) was discovered by the Distance Less Than 40 Mpc Survey (DLT40) on 2 April 2018. It reached magnitude 12.7, making it tied with SN 2018pv for the brightest supernova of 2018.

Nearby galaxies NGC 3923 is the brightest galaxy in a galaxy group known as the NGC 3923 galaxy group. Seven dwarf elliptical galaxies within 25 arcminutes of NGC 3923 have been detected. NGC 3904 is located 37 arcminutes away. Other galaxies in the group include NGC 3885, ESO 440-27, and ESO 440-11. Other nearby galaxies include NGC 3617, NGC 3673, NGC 3717, NGC 3936, and NGC 4105.

See also List of NGC objects (3001–4000)

References

This article incorporates text available under the CC BY 4.0 license.

External links

NGC 3923 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 3923

Start with the simplest possible case. Write down what NGC 3923 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 3923 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 3923 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 3923

In research: NGC 3923 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 3923 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 3923 is common in secondary-school and first-year university syllabi. It links to neighbouring topics Astronomical objects discovered in 1791, Discoveries by William Herschel, ESO objects, so understanding it makes those chapters shorter.
In everyday life: Look for NGC 3923 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 3923 in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what NGC 3923 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 3923 out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is NGC 3923 in simple terms?

Why does NGC 3923 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 3923?

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 3923.