astronomy

WR 24

WR 24 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 WR 24 rather than just read about it. In short: WR 24 (HD 93131) is a Wolf-Rayet star in the constellation Carina. It is one of the most luminous stars known.

Key takeaways

WR 24 belongs to astronomy; place it in that map before memorising details.
Learn the definition first, then one example that makes the definition concrete.
Connect WR 24 to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of WR 24 from memory before moving on to harder problems.

Reference excerpt

WR 24 (HD 93131) is a Wolf-Rayet star in the constellation Carina. It is one of the most luminous stars known. At the edge of naked eye visibility it is also one of the brightest Wolf Rayet stars in the sky. The spectrum of WR 24 has the characteristic strong nitrogen and helium emission lines of a WN star, but also lines of hydrogen that show Doppler-displaced absorption components. The lowest ionisation nitrogen emission lines are strongest, with NV lines being very weak. The HeI lines are weaker than the HeII lines, leading to a WN6ha spectral class. The spectral type is annotated with a letter w, indicating weaker emission than for a typical WN6 star. WR 24 is thought to be a member of the open cluster Collinder 228, sometimes considered to be just an extension of the rich cluster Trumpler 16. It lies on the southwestern side of the Carina Nebula. Collinder 228 and the Carina Nebula are approximately 2.2 kpc away. However, the Gaia Data Release 2 parallax gives a distance around 4200 for WR 24.

WR 24 has been reported to vary in brightness by about 0.02 magnitudes. Analysis of Hipparcos photometry shows an amplitude of 0.082 magnitudes and a primary period of 4.76 days. It has not yet been assigned a variable star designation in the General Catalogue of Variable Stars and is still formally listed as a suspected variable. The hydrogen-rich WN stars have been referred to as WNL stars or as WNH stars since they do not necessarily have late nitrogen-sequence spectra. They are systematically more massive and more luminous than stars with similar spectra but lacking nitrogen. WR 24 has a mass of 114 M☉ and is nearly three million times as luminous as the sun. These stars are proposed to be young hydrogen-burning stars, effectively main sequence objects, rather than post-supergiant stars. WR 24 is calculated to have 44% hydrogen in its atmosphere. The cluster Collinder 228 is thought to be around 6.78 million years old. The WR-type spectra are caused because helium and nitrogen and convected to the surface by the extreme temperature gradients caused by the CNO cycle in the core, and then expelled by powerful stellar winds. WR 24 has a wind reducing its mass by 40×10−6 M☉ per year, at a velocity of 2,160 km/s.

Illustrations

Worked examples

Example 1 — a first encounter with WR 24

Start with the simplest possible case. Write down what WR 24 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 WR 24 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 WR 24 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 WR 24

In research: WR 24 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 WR 24 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: WR 24 is common in secondary-school and first-year university syllabi. It links to neighbouring topics Carina (constellation), Durchmusterung objects, Henry Draper Catalogue objects, so understanding it makes those chapters shorter.
In everyday life: Look for WR 24 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 WR 24 in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what WR 24 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 WR 24 out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is WR 24 in simple terms?

WR 24 (HD 93131) is a Wolf-Rayet star in the constellation Carina. It is one of the most luminous stars known.

Why does WR 24 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 WR 24?

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 WR 24.