astronomy

HD 101917

HD 101917 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 101917 rather than just read about it. In short: HD 101917, also designated as HR 4509, or rarely 34 G. Chamaeleontis, is a solitary star located in the southern circumpolar constellation Chamaeleon.

Key takeaways

HD 101917 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 101917 to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of HD 101917 from memory before moving on to harder problems.

Reference excerpt

HD 101917, also designated as HR 4509, or rarely 34 G. Chamaeleontis, is a solitary star located in the southern circumpolar constellation Chamaeleon. It has an apparent magnitude of 6.38, placing it near the limit for naked eye visibility. The object is located relatively close at a distance of 185 light years based on Gaia DR3 parallax measurements but is receding with a heliocentric radial velocity of 33 km/s. At its current distance, HD 101917's brightness is diminished by 0.28 magnitudes due to interstellar dust. It has an absolute magnitude of +2.69. HD 101917 has a stellar classification of K0 III/IV, indicating that it is an evolved K-type star with the blended luminosity class of a subgiant and a giant star. Gaia DR3 models it to be 3.9 billion years old, enough time for it to cool and expand to 4.01 times the radius of the Sun. At present it has 126% the mass of the Sun and now radiates 9.04 times the luminosity of the Sun from its enlarged photosphere at an effective temperature 5,076 K, giving it a yellow hue. HD 101917 has an iron abundance 22% below solar levels, making it slightly metal deficient. It spins slowly with a projected rotational velocity lower than 1.4 km/s.

References

Illustrations

Worked examples

Example 1 — a first encounter with HD 101917

Start with the simplest possible case. Write down what HD 101917 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 101917 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 101917 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 101917

In research: HD 101917 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 101917 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 101917 is common in secondary-school and first-year university syllabi. It links to neighbouring topics Bright Star Catalogue objects, Chamaeleon, Durchmusterung objects, so understanding it makes those chapters shorter.
In everyday life: Look for HD 101917 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 101917 in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what HD 101917 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 101917 out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is HD 101917 in simple terms?

HD 101917, also designated as HR 4509, or rarely 34 G. Chamaeleontis, is a solitary star located in the southern circumpolar constellation Chamaeleon.

Why does HD 101917 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 101917?

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 101917.