astronomy

HD 93486

HD 93486 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 93486 rather than just read about it. In short: HD 93486, also known as HIP 52381, is a binary star located in the southern circumpolar constellation Chamaeleon near the border with Octans. Its variable star designation is RZ Chamaeleontis (RZ Cha).

Key takeaways

HD 93486 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 93486 to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of HD 93486 from memory before moving on to harder problems.

Reference excerpt

HD 93486, also known as HIP 52381, is a binary star located in the southern circumpolar constellation Chamaeleon near the border with Octans. Its variable star designation is RZ Chamaeleontis (RZ Cha). It has an apparent magnitude ranging from 8.2 to 9.1, which is below the limit for naked eye visibility. Gaia DR3 parallax measurements place the system 568 light years away, and it is currently receding with a heliocentric radial velocity of 20 km/s. At its current distance, HD 93486's average brightness is diminished by 0.53 magnitudes due to interstellar dust. The system has a combined absolute magnitude of +1.72. In 1964, HD 93486 was discovered to be an eclipsing binary by astronomer W. Strohmeier and colleagues. Four years later, the system was found to be an Algol variable and was given the variable star designation RZ Chamaeleontis in 1974. J. Andersen et al. (1975) calculated a circular orbit of 2.8321 days, which is also its variability period. During this time, RZ Cha drops from photographic magnitude 8.2 to 9.1 when the smaller component is eclipsed, and to 8.8 when the larger one is eclipsed. Both components have a stellar classification of F5 IV-V, indicating that they are slightly evolved F-type stars with luminosity classes intermediate between a subgiant and a main-sequence star. The primary has 149% the mass of the Sun and 2.15 times the Sun's radius. The secondary has 148% the mass of the Sun and 2.27 times the radius of the Sun. Together, both stars radiate 7.94 times the luminosity of the Sun from their photospheres at an effective temperature of 6,450 K, giving it a combined yellowish-white hue. The system is metal enriched with an iron abundance and is estimated to be 2 to 3 billion years old. Both stars spin modestly, with projected rotational velocities of 38.4 km/s and 40.6 km/s respectively.

References

Further reading Dryomova, G. N.; Svechnikov, M. A. (April 2007). "Effect of tidal evolution in determining the ages of eclipsing-variable early main sequence close binary systems". Astrophysics. 50 (2): 239–253. Bibcode:2007Ap.....50..239D. doi:10.1007/s10511-007-0023-9. eISSN 1573-8191. ISSN 0571-7256. S2CID 121459015.

Illustrations

Worked examples

Example 1 — a first encounter with HD 93486

Start with the simplest possible case. Write down what HD 93486 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 93486 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 93486 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 93486

In research: HD 93486 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 93486 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 93486 is common in secondary-school and first-year university syllabi. It links to neighbouring topics Algol variables, Chamaeleon, Durchmusterung objects, so understanding it makes those chapters shorter.
In everyday life: Look for HD 93486 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 93486 in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what HD 93486 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 93486 out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is HD 93486 in simple terms?

Why does HD 93486 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 93486?

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 93486.