astronomy

NGC 4688

NGC 4688 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 4688 rather than just read about it. In short: NGC 4688 is a barred spiral galaxy in the constellation of Virgo. Its velocity with respect to the cosmic microwave background is 1,318±23 km/s, which corresponds to a Hubble distance of 63.4 ± 4.6 Mly (19.44 ± 1.40 Mpc).

Key takeaways

NGC 4688 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 4688 to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of NGC 4688 from memory before moving on to harder problems.

Reference excerpt

NGC 4688 is a barred spiral galaxy in the constellation of Virgo. Its velocity with respect to the cosmic microwave background is 1,318±23 km/s, which corresponds to a Hubble distance of 63.4 ± 4.6 Mly (19.44 ± 1.40 Mpc). However, five non-redshift measurements give a much closer mean distance of 24.79 ± 8.02 Mly (7.600 ± 2.458 Mpc). It was discovered by German-British astronomer William Herschel on 17 April 1786. NGC 4688 has a possible active galactic nucleus, i.e. it has a compact region at the center of a galaxy that emits a significant amount of energy across the electromagnetic spectrum, with characteristics indicating that this luminosity is not produced by the stars. It is also a LINER galaxy, i.e. a galaxy whose nucleus has an emission spectrum characterized by broad lines of weakly ionized atoms.

M49 group According to A. M. Garcia, NGC 4688 is a member of the M49 group (also known as LGG 292). This group includes 63 galaxies from the New General Catalogue, including Messier 49, Messier 85, NGC 4516, Messier 60, and 20 galaxies from the Index Catalogue.

Supernova One supernova has been observed in NGC 4688:

SN 1966B (Type II, mag. 15.5) was discovered by D. Ya. Martynov on 12 February 1966. Howard S. Gates had photographed it earlier, on 25 January 1966, but he suspected the object might be a minor planet, and delayed the announcement until a confirmation picture could be taken, thus losing credit for the discovery.

See also List of NGC objects (4001–5000)

References

External links Media related to NGC 4688 at Wikimedia Commons NGC 4688 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 4688

Start with the simplest possible case. Write down what NGC 4688 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 4688 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 4688 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 4688

In research: NGC 4688 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 4688 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 4688 is common in secondary-school and first-year university syllabi. It links to neighbouring topics Astronomical objects discovered in 1786, Barred spiral galaxies, Discoveries by William Herschel, so understanding it makes those chapters shorter.
In everyday life: Look for NGC 4688 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 4688 in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what NGC 4688 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 4688 out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is NGC 4688 in simple terms?

Why does NGC 4688 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 4688?

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 4688.