astronomy

WR 137

WR 137 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 137 rather than just read about it. In short: WR 137 is a variable Wolf-Rayet star located around 6,000 light years away from Earth in the constellation of Cygnus. WR 137, together with WR 134 and WR 135, was one of three stars in Cygnus observed in 1867 to have unusual spectra consisting of intense emission lines rather than the more normal continuum and absorption lines.

Key takeaways

WR 137 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 137 to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of WR 137 from memory before moving on to harder problems.

Reference excerpt

WR 137 is a variable Wolf-Rayet star located around 6,000 light years away from Earth in the constellation of Cygnus. WR 137, together with WR 134 and WR 135, was one of three stars in Cygnus observed in 1867 to have unusual spectra consisting of intense emission lines rather than the more normal continuum and absorption lines. These were the first members of the class of stars that came to be called Wolf-Rayet stars (WR stars) after Charles Wolf and Georges Rayet who discovered their unusual appearance. It is a member of the carbon sequence of WR stars, indicated by the lack of nitrogen lines and the strength of carbon emission. WR 137 has a spectrum with CIII emission weaker than CIV and OV weaker still, leading to the assignment of a WC7 spectral type. The spectrum also shows emission lines of HeII and OIV.

WR 137 is a binary system, with an O9 main sequence or giant companion. The two stars orbit every thirteen years in a mildly eccentric orbit, and there is an episode of dust production near periastron. The inclination of the orbit is high, near 97 degrees. The O star is visually brighter and more massive, but the WR star dominates the spectrum and has a higher bolometric luminosity. Visible in the spectrum are absorption lines and some narrow emission lines, each thought to originate from the secondary star. The line profiles suggest a decretion disc around the star, produced by its rapid rotation, which would make it the only known system containing a WR star and an Oe star. WR 137 is about a degree away from WR 135 and the two are believed to lie at approximately the same distance from Earth within the Cygnus OB3 association. Its properties are uncertain because of the presence of the hot luminous companion. A pseudo-fit of the combined spectrum yielded a temperature of 56,000 K, a luminosity of 537,000 L☉, and a radius of 10 R☉. A more typical radius for a WC7 star would be 4.5 R☉, implying a hotter temperature. Evolutionary modelling of the WR 137 pair suggest an initial mass for the primary of 60 M☉ and for the secondary of 30 M☉, with an age of 4.1 million years. The initial orbital period would have been around 1,580 days. Around three M☉ have been transferred from the primary to the secondary. Observations with JWST instrument MIRI did resolve 10 rings around the binary, representing 131 years of dust ejection. The dust moves with a speed of 1700 km/s, near the terminal velocity. Each ring represents a dust plume, which starts to form near a quadrature in their orbit and continues after the conjunction. This results in dust being seen in both directions along the nearly edge-on orbital plane.

References

External links Wolf-Rayet shells showing a spectrum of WR 135 WR134 Ring Nebula with WR 135 visible in the top left corner

Illustrations

Worked examples

Example 1 — a first encounter with WR 137

Start with the simplest possible case. Write down what WR 137 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 137 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 137 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 137

In research: WR 137 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 137 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 137 is common in secondary-school and first-year university syllabi. It links to neighbouring topics Cygnus (constellation), Durchmusterung objects, Henry Draper Catalogue objects, so understanding it makes those chapters shorter.
In everyday life: Look for WR 137 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 137 in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what WR 137 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 137 out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is WR 137 in simple terms?

Why does WR 137 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 137?

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 137.