astronomy

V686 Coronae Australis

V686 Coronae Australis 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 V686 Coronae Australis rather than just read about it. In short: V686 Coronae Australis (HD 175362; HR 7129; V686 CrA) is a solitary, bluish-white-hued variable star located in the southern constellation Corona Australis. It has an apparent magnitude that ranges between 5.25 and 5.41, which makes it faintly visible to the naked eye.

Key takeaways

V686 Coronae Australis belongs to astronomy; place it in that map before memorising details.
Learn the definition first, then one example that makes the definition concrete.
Connect V686 Coronae Australis to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of V686 Coronae Australis from memory before moving on to harder problems.

Reference excerpt

V686 Coronae Australis (HD 175362; HR 7129; V686 CrA) is a solitary, bluish-white-hued variable star located in the southern constellation Corona Australis. It has an apparent magnitude that ranges between 5.25 and 5.41, which makes it faintly visible to the naked eye. Gaia DR3 parallax measurements imply a distance of 480 light years and it is slowly receding with a heliocentric radial velocity of 1.3 km/s. At its current distance V686 CrA's average brightness is diminished by 0.35 magnitudes due to extinction from interstellar dust and it has an absolute visual magnitude of −0.24. V686 CrA has been known to be variable since 1974. The discovery paper lists it as a helium variable with a period of 3.71 days. Earlier sources give it ordinary spectral classes such as B7.5 V, B8 IV. and B9 III:. In 1976, V686 CrA was found to have a large magnetic field ranging from −5,000 gauss to 7,000 gauss. Borra et al. (1983) gave a value of −6,500–4,800 gauss. A catalogue of chemically peculiar stars gives a spectral class of B6 He wk. Si, indicating it is a helium-weak star. It has also been classified as a mercury-manganese star.

V686 CrA is an α2 Canum Venaticorum variable that ranges from 5.25 to 5.41 within 3.674 days. It has been proposed that the rotation period of the star, and hence the true variability period, is 7.34 days, with two near-identical minima in the light curve. It is a member of the Scorpius-Centaurus association and the Local Association. The accepted stellar classification for V686 CrA is B3V, indicating that it is B-type main sequence star. It has 4.73 times the mass of the Sun and 3.52 times the Sun's radius. It radiates 504 times the luminosity of the Sun from its photosphere at an effective temperature of 16,482 K V686 has an unusually high metallicity of [Fe/H] = +1.13, which is over 10 times that of the sun. This only accounts for the spectrum of the star and not its entire composition. Like most chemically peculiar stars it spins rather slowly, having a projected rotational velocity of 45.4 km/s. Based on analysis of its surface magnetic fields, V686 CrA is estimated to be 63 million years old, although other sources give a much younger age: for example, 7.9 million years having completed only 0.9% of its main sequence lifetime.

References

Illustrations

Worked examples

Example 1 — a first encounter with V686 Coronae Australis

Start with the simplest possible case. Write down what V686 Coronae Australis 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 V686 Coronae Australis 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 V686 Coronae Australis 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 V686 Coronae Australis

In research: V686 Coronae Australis 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 V686 Coronae Australis 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: V686 Coronae Australis is common in secondary-school and first-year university syllabi. It links to neighbouring topics Alpha2 Canum Venaticorum variables, B-type main-sequence stars, Bright Star Catalogue objects, so understanding it makes those chapters shorter.
In everyday life: Look for V686 Coronae Australis 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.

Ask Teacher Smith questions about this articleOpens your AI tutor with a question about “V686 Coronae Australis” →

Affiliate

Preply — study more efficiently by working with a personal tutor. 50% off.

How to study V686 Coronae Australis in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what V686 Coronae Australis 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 V686 Coronae Australis out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is V686 Coronae Australis in simple terms?

Why does V686 Coronae Australis 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 V686 Coronae Australis?

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 V686 Coronae Australis.