astronomy

IC 1689

IC 1689 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 IC 1689 rather than just read about it. In short: IC 1689 is a lenticular galaxy located in the constellation of Pisces. The redshift of the galaxy is (z) 0.015 and it was first discovered by the French astronomer named Stephane Javelle in December 1899, who described it as a faint object with a bright central nucleus.

Key takeaways

IC 1689 belongs to astronomy; place it in that map before memorising details.
Learn the definition first, then one example that makes the definition concrete.
Connect IC 1689 to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of IC 1689 from memory before moving on to harder problems.

Reference excerpt

IC 1689 is a lenticular galaxy located in the constellation of Pisces. The redshift of the galaxy is (z) 0.015 and it was first discovered by the French astronomer named Stephane Javelle in December 1899, who described it as a faint object with a bright central nucleus. This galaxy has also been described as a polar ring galaxy.

Description IC 1689 is categorized as a normal lenticular galaxy with a type S0 morphology. The galaxy has a peculiar appearance, with a clumpy structure that is located on its outer regions. The ring structure of the galaxy is, however, found to be small, while the central region is depicted to have a boxy-like appearance. The disk of the galaxy is also wrapped with the position angles somehow shifted by about 11°. The ring is symmetrical, while the surface brightness decreases at a steep side on the inner border and at a flat side on the outer border. The inner ring has a radius of about 1.2 kiloparsecs, while the outer ring is about 3.2 kiloparsecs. A study published in 1996, has found IC 1689 contains an active central nucleus displaying low ionization spectral line emission that is extended from it. As the gas from its disk is weakly accreted into its nucleus, the galaxy is said to be classified as a LINER galaxy. Further evidence also finds the star formation only occurs in the outer regions of the disk. Hydrogen-alpha emission is present, mainly being concentrated in at least two regions, with ionized nitrogen emission detected inside the central region, indicating there is a rotating gaseous disk in a plane perpendicular to the galaxy's main plane. A magnesium line has also been detected, located in both the nucleus region and the radius region by 5.5 arcseconds where the ring feature is crossing the major axis. IC 1689 is a member of the NGC 507 group. Known as LGG 26, the group comprises multiple galaxies, including NGC 507, IC 1687, IC 1690, NGC 501, NGC 512, NGC 528, NGC 523, NGC 483, NGC 536, NGC 587, NGC 591, Markarian 980, NGC 608, NGC 531, NGC 542, UGC 937, UGC 987, PGC 5100 and IC 1666.

References

External links IC 1689 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 IC 1689

Start with the simplest possible case. Write down what IC 1689 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 IC 1689 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 IC 1689 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 IC 1689

In research: IC 1689 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 IC 1689 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: IC 1689 is common in secondary-school and first-year university syllabi. It links to neighbouring topics Active galaxies, Astronomical objects discovered in 1899, IC objects, so understanding it makes those chapters shorter.
In everyday life: Look for IC 1689 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 IC 1689 in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what IC 1689 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 IC 1689 out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is IC 1689 in simple terms?

Why does IC 1689 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 IC 1689?

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 IC 1689.