astronomy

NGC 4654

NGC 4654 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 4654 rather than just read about it. In short: NGC 4654 is an intermediate spiral galaxy in the constellation of Virgo. Its velocity with respect to the cosmic microwave background is 1,356±22 km/s, which corresponds to a Hubble distance of 65.2 ± 4.7 Mly (20.00 ± 1.44 Mpc).

Key takeaways

NGC 4654 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 4654 to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of NGC 4654 from memory before moving on to harder problems.

Reference excerpt

NGC 4654 is an intermediate spiral galaxy in the constellation of Virgo. Its velocity with respect to the cosmic microwave background is 1,356±22 km/s, which corresponds to a Hubble distance of 65.2 ± 4.7 Mly (20.00 ± 1.44 Mpc). However, 34 non-redshift measurements give a closer mean distance of 47.97 ± 1.75 Mly (14.708 ± 0.536 Mpc).. It was discovered by German-British astronomer William Herschel on 12 April 1784. It is bright enough that it can be seen using amateur telescopes.

Physical characteristics

NGC 4654 is a member of the Virgo Cluster of galaxies that shows peculiarities in the distribution of both its atomic hydrogen and molecular hydrogen as well as an asymmetry on the distribution of its stars, with the atomic hydrogen being compressed in the galaxy's northwestern part and forming a tail on its southeastern part. While interactions with Virgo's intracluster medium - that is stripping NGC 4654 of its gas as the galaxy moves through it - can explain its gas distribution, it is unable to explain the peculiarities in the distribution of its stars. It has been proposed that NGC 4654 interacted with its neighbor the spiral galaxy NGC 4639 about 500 million years ago; this, combined with weak ram-pressure stripping due to its motion within the Virgo cluster, may explain its features. Despite suffering a loss of its neutral gas, NGC 4654 does not suffer the deficiency of it that is shown in many spiral galaxies of the Virgo cluster and also has the star formation typical for a galaxy of its type.

See also Messier 88, another spiral galaxy of the Virgo cluster currently suffering ram-pressure stripping. NGC 4457 List of NGC objects (4001–5000)

References

External links Media related to NGC 4654 at Wikimedia Commons

Illustrations

Worked examples

Example 1 — a first encounter with NGC 4654

Start with the simplest possible case. Write down what NGC 4654 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 4654 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 4654 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 4654

In research: NGC 4654 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 4654 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 4654 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 4654 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 4654 in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what NGC 4654 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 4654 out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is NGC 4654 in simple terms?

Why does NGC 4654 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 4654?

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 4654.