astronomy

WR 142

WR 142 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 142 rather than just read about it. In short: WR 142 is a Wolf–Rayet star in the constellation Cygnus, an extremely rare star on the WO oxygen sequence. It is a luminous and very hot star, highly evolved and close to exploding as a supernova.

Key takeaways

WR 142 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 142 to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of WR 142 from memory before moving on to harder problems.

Reference excerpt

WR 142 is a Wolf–Rayet star in the constellation Cygnus, an extremely rare star on the WO oxygen sequence. It is a luminous and very hot star, highly evolved and close to exploding as a supernova. It is suspected to be a binary star with a companion orbiting about 1 au away.

Discovery

In 1966, a search for Wolf–Rayet stars in the northern celestial hemisphere discovered seven new examples. One, designated as Stephenson 3, was classified as WC. It was later found to show unusual emission lines of highly ionised OVI. Because of the unusual oxygen lines, seen in only a handful of other stars, it was given the spectral type WC5pec in the Sixth Catalogue of Galactic Wolf–Rayet Stars. In 1981, described as a WC-OVI star, it was identified as being associated with the active star-forming region ON2, and then a heavily obscured open cluster designated Berkeley 87, 9.5′ south of the red supergiant BC Cygni. In 1982, the WC-OVI stars were grouped as members of the new WO class. The class at that time consisted of five stars, two of which were in the Magellanic Clouds and one of which was later found to be the central star of a planetary nebula.

Features WR 142 is usually assumed to be a member of the open cluster Berkeley 87, whose distance from the Sun is not very well known but thought to be around 1.23 kiloparsecs (4,000 light-years). As with its home cluster its light is very reddened and extinguished by interstellar dust. This star, of spectral classification WO2, is one of the very few known oxygen-sequence Wolf–Rayet stars, just four in the Milky Way galaxy and six in external galaxies. It is also one of the hottest known with a surface temperature of 200,000 K. Modelling the atmosphere gives a luminosity around 245,000 L☉, while calculations from brightness and distance give luminosities of 500,000 L☉ or more. According to Gaia DR2's distance, it could be as much as 912,000 L☉. It is a very small dense star, with a radius of just 80% of the Sun's but a mass of nearly 29 times greater. Very strong stellar winds, with a terminal velocity of 5,000 kilometers per second are causing WR 142 to lose roughly 1.6×10−5 M☉/year. For comparison, the Sun loses (2–3)×10−14 M☉/year due to its solar wind, several hundred million times less than WR 142. Hard X-ray emission has been detected from this star with the help of the Chandra space telescope, that has been suggested to be caused by the presence of a companion, a B-type main sequence star located at a distance of 1 au from WR 142. There is no other indication of a companion and other reasons for the x-ray luminosity are considered more likely.

Evolutionary status WO Wolf–Rayet stars are the last evolutionary stage of the most massive stars before exploding as supernovae, possibly with a gamma-ray burst (GRB). It is very likely that WR 142 is on its last stages of nuclear fusion, near or beyond the end of helium burning. It is estimated to explode as a supernova in approximately 2,000 years. The mass and rapid rotation make a GRB likely.

See also WR 102 WR 30a WR 93b List of supernova candidates

References

Worked examples

Example 1 — a first encounter with WR 142

Start with the simplest possible case. Write down what WR 142 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 142 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 142 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 142

In research: WR 142 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 142 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 142 is common in secondary-school and first-year university syllabi. It links to neighbouring topics Cygnus (constellation), Population I stars, Wolf–Rayet stars, so understanding it makes those chapters shorter.
In everyday life: Look for WR 142 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 142 in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what WR 142 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 142 out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is WR 142 in simple terms?

WR 142 is a Wolf–Rayet star in the constellation Cygnus, an extremely rare star on the WO oxygen sequence. It is a luminous and very hot star, highly evolved and close to exploding as a supernova.

Why does WR 142 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 142?

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 142.