astronomy

IC 239

IC 239 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 239 rather than just read about it. In short: IC 239 is a spiral galaxy in the constellation Andromeda. The galaxy lies about 35 million light years away from Earth, which means, given its apparent dimensions, that IC 239 is approximately 50,000 light years across.

Key takeaways

IC 239 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 239 to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of IC 239 from memory before moving on to harder problems.

Reference excerpt

IC 239 is a spiral galaxy in the constellation Andromeda. The galaxy lies about 35 million light years away from Earth, which means, given its apparent dimensions, that IC 239 is approximately 50,000 light years across. It was discovered by Isaac Roberts in 1893.

Characteristics The galaxy is seen nearly face on. The bulge of the galaxy is small and embedded in a thick bar. From its end of the bar emerge two low surface brightness arms that can be traced for half a revolution before fading, with a grand design pattern. The galaxy also has a faint outer third arm. The galaxy has a hydrogen I disk which extends for about twice the optical radius of the galaxy and appears warped. However the galaxy doesn't appear to be interacting with other galaxies.

Nearby galaxies IC 239 is located in the vicinity of the NGC 1023 Group. Garcia considered the galaxy to be a member of the group, also known as LGG 70, along with NGC 1023 and NGC 1003. The angular separation of NGC 1023 and IC 239 is 47 arcminutes, while DDO 22 is located 45 arcminutes to the west. However the galaxy, although appearing centrally in the group in the sky, has a radial velocity higher than that of the other members of the group, indicating it is lying in the background. Makarov and Karachentsev consider the galaxy a member of the IC 239 group, along with NGC 1023C, and is located in the same galaxy cloud with NGC 1023 and its group.

References

External links

IC 239 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 239

Start with the simplest possible case. Write down what IC 239 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 239 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 239 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 239

In research: IC 239 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 239 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 239 is common in secondary-school and first-year university syllabi. It links to neighbouring topics Andromeda (constellation), Astronomical objects discovered in 1893, IC objects, so understanding it makes those chapters shorter.
In everyday life: Look for IC 239 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 239 in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what IC 239 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 239 out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is IC 239 in simple terms?

Why does IC 239 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 239?

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 239.