astronomy

HD 120213

HD 120213 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 HD 120213 rather than just read about it. In short: HD 120213 (HR 5188) is a solitary star in the southern circumpolar constellation Chamaeleon. It is faintly visible to the naked eye with an apparent magnitude of 5.94 and is estimated to be 910 light years away from the Solar System.

Key takeaways

HD 120213 belongs to astronomy; place it in that map before memorising details.
Learn the definition first, then one example that makes the definition concrete.
Connect HD 120213 to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of HD 120213 from memory before moving on to harder problems.

Reference excerpt

HD 120213 (HR 5188) is a solitary star in the southern circumpolar constellation Chamaeleon. It is faintly visible to the naked eye with an apparent magnitude of 5.94 and is estimated to be 910 light years away from the Solar System. However, the object is drifting closer with a heliocentric radial velocity of −35 km/s. HD 120213 has a stellar classification of K2 III: CN−1 CH −2.5, indicating that its a red giant with an under abundance of CH molecules and cyano radicals in its spectrum. It has also been classified as a mild barium star, but there is uncertainty about the spectral class. It has 4.2 times the mass of the Sun and an enlarged radii of 38.6 R☉. It shines at 503 times the luminosity of the Sun from its photosphere at an effective temperature of 4,401 K, giving it an orange hue. HD 120213 has a metallicity 56% that of the Sun and spins with a projected rotational velocity too low to be accurately measured.

References

Worked examples

Example 1 — a first encounter with HD 120213

Start with the simplest possible case. Write down what HD 120213 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 HD 120213 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 HD 120213 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 HD 120213

In research: HD 120213 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 HD 120213 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: HD 120213 is common in secondary-school and first-year university syllabi. It links to neighbouring topics Barium stars, Bright Star Catalogue objects, Chamaeleon, so understanding it makes those chapters shorter.
In everyday life: Look for HD 120213 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 HD 120213 in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what HD 120213 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 HD 120213 out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is HD 120213 in simple terms?

Why does HD 120213 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 HD 120213?

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 HD 120213.