astronomy

WR 120

WR 120 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 120 rather than just read about it. In short: WR 120 is a binary containing two Wolf–Rayet stars in the constellation of Scutum, around 10,000 light years away. The primary is a hydrogen-free weak-lined WN7 star, the secondary is a hydrogen-free WN3 or 4 star, and the system is a possible member of the cluster Dolidze 33.

Key takeaways

WR 120 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 120 to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of WR 120 from memory before moving on to harder problems.

Reference excerpt

WR 120 is a binary containing two Wolf–Rayet stars in the constellation of Scutum, around 10,000 light years away. The primary is a hydrogen-free weak-lined WN7 star, the secondary is a hydrogen-free WN3 or 4 star, and the system is a possible member of the cluster Dolidze 33. From our point of view, WR 120 is reddened by 4.82 magnitudes. Photometric observations obtained in 1995 by Sergey V. Marchenko et al. showed that WR 120 is a variable star. For that reason it was given its variable star designation, V462 Scuti, in the year 2000.

Properties Analysis of the primary's spectrum with PoWR shows that it has a temperature of around 50,000 Kelvins, and is losing mass at a rate of 10−4.9 M☉/year, or 1 solar mass every 80,000 years, which is being carried away from the surface at a speed of 1,225 kilometres per second. Taking its close distance into account, WR 120 A's luminosity turns out to be a mere 83,200 L☉, which would make it one of the dimmest WN stars known, and one of the only WN stars with a luminosity below 100,000 L☉. Using the Stefan-Boltzmann Law, a radius of 3.78 R☉ is derived, and a "transformed" radius at an optical depth of 2/3, more comparable to other types of stars, is about 6 R☉. Using the WR luminosity-mass ratio, WR 120 may have a mass of just 7 M☉, one of the lowest masses of any WR star. WR 120's absolute magnitude is −3.8, which is also relatively faint for a Wolf–Rayet star. WR 120 is thought to be a member of Dolidze 33, an open cluster nearly 3,000 pc away.

Binarity In 2021, WR 120 was found to have a close companion. Previously, it was thought to be a single WR star. The companion is thought to be a WN3/4 WR star and would be located at least 1,700 AU from the primary WN7 WR star. It is about two magnitudes fainter than WR 120.

References

Illustrations

Worked examples

Example 1 — a first encounter with WR 120

Start with the simplest possible case. Write down what WR 120 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 120 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 120 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 120

In research: WR 120 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 120 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 120 is common in secondary-school and first-year university syllabi. It links to neighbouring topics Binary stars, Objects with variable star designations, Scutum (constellation), so understanding it makes those chapters shorter.
In everyday life: Look for WR 120 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 120 in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what WR 120 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 120 out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is WR 120 in simple terms?

Why does WR 120 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 120?

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 120.