astronomy

IC 2402

IC 2402 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 2402 rather than just read about it. In short: IC 2402 known in literature as B0844+31 or B2 0844+31, is a large elliptical galaxy located in the constellation of Cancer. The galaxy is located around 940 million light-years from Earth, which means given by its apparent dimensions, it is 370,000 light-years across.

Key takeaways

IC 2402 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 2402 to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of IC 2402 from memory before moving on to harder problems.

Reference excerpt

IC 2402 known in literature as B0844+31 or B2 0844+31, is a large elliptical galaxy located in the constellation of Cancer. The galaxy is located around 940 million light-years from Earth, which means given by its apparent dimensions, it is 370,000 light-years across. It was first discovered by Stéphane Javelle on 15 February 1896 and subsequently designated as 4C 31.32 by astronomers.

Description IC 2402 is the brightest cluster galaxy (BCG) of the galaxy cluster ZW 0844.5+3208. It is classified as a narrow-line Fanaroff-Riley type 2 (FR II) radio galaxy or a double low-luminosity radio galaxy. It has a brightness profile best described as following the de Vancouleurs law with isophotes twisted by 30 degrees from its nucleus to the external parts of the galaxy. The radio structure of the galaxy imaged by radio mapping at 0.6 and 1.4 GHz frequencies shows a double source displaying low intensity regions along its eastern side. The two components of the source have an increased spectral index towards the north, with the central region dominated by a core. A radio jet can be seen, which subsequently becomes fainter and wider upon travelling from the core. Resolving into a main jet and counter-jet, they both display sine wave type oscillations. The radio lobes of the galaxy are polarized and symmetrical. However, the southern radio lobe is significantly depolarized compared to the northern radio lobe, displaying depolarization ratios of 0.45 ± 0.1 and 0.85 ± 0.1, but it has a positive rotation measure of 25 rad m−2. Both lobes are shown to have spectral index variations, with the outer ridges of the radio emission having spectral indices of ~0.8–0.9 and ~1.0 respectively. The lobes also contain hot spots which are anti-symmetric in appearance. A study published in 2005, shows the galaxy's radio lobes are classified as Fanaroff-Riley type 1 (FR I) according to a Faint Images of the Radio Sky at Twenty-Centimeters (FIRST) survey conducted by Very Large Array (VLA). Further evidence also pointed out these lobes are located far from the nucleus beyond the hotspots, suggesting the source can be categorized as restarted; a source best described having an FR I extended structure relating to prior activity whereas the FR II inner structure is originating from recent activity from the core.

References

External links IC 2402 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 2402

Start with the simplest possible case. Write down what IC 2402 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 2402 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 2402 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 2402

In research: IC 2402 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 2402 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 2402 is common in secondary-school and first-year university syllabi. It links to neighbouring topics 4C objects, Active galaxies, Astronomical objects discovered in 1896, so understanding it makes those chapters shorter.
In everyday life: Look for IC 2402 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 2402 in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what IC 2402 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 2402 out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is IC 2402 in simple terms?

Why does IC 2402 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 2402?

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 2402.