astronomy

NGC 7689

NGC 7689 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 7689 rather than just read about it. In short: NGC 7689 is an intermediate spiral galaxy in the constellation of Phoenix. Its velocity with respect to the cosmic microwave background is 1,791±13 km/s, which corresponds to a Hubble distance of 86.2 ± 6.1 Mly (26.42 ± 1.86 Mpc).

Key takeaways

NGC 7689 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 7689 to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of NGC 7689 from memory before moving on to harder problems.

Reference excerpt

NGC 7689 is an intermediate spiral galaxy in the constellation of Phoenix. Its velocity with respect to the cosmic microwave background is 1,791±13 km/s, which corresponds to a Hubble distance of 86.2 ± 6.1 Mly (26.42 ± 1.86 Mpc). Also, 13 non-redshift measurements give a closer mean distance of 79.30 ± 1.36 Mly (24.315 ± 0.417 Mpc). It was discovered by Scottish astronomer James Dunlop on 5 September 1826. NGC 7689 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 Seyfert II galaxy, i.e. it has a quasar-like nucleus with very high surface brightnesses whose spectra reveal strong, high-ionisation emission lines, but unlike quasars, the host galaxy is clearly detectable.

Supernova One supernova has been observed in NGC 7689:

SN 1996al (Type II, mag. 14.0) was discovered by Robert Evans, R. Benton, and S. Beaman on 22 July 1996.

Image gallery

See also List of NGC objects (7001–7840)

References

External links Media related to NGC 7689 at Wikimedia Commons NGC 7689 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 7689

Start with the simplest possible case. Write down what NGC 7689 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 7689 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 7689 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 7689

In research: NGC 7689 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 7689 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 7689 is common in secondary-school and first-year university syllabi. It links to neighbouring topics Astronomical objects discovered in 1826, Discoveries by James Dunlop, ESO objects, so understanding it makes those chapters shorter.
In everyday life: Look for NGC 7689 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 7689 in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what NGC 7689 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 7689 out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is NGC 7689 in simple terms?

Why does NGC 7689 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 7689?

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 7689.