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astronomy

R85

R85 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 R85 rather than just read about it. In short: R85 (or RMC 85, after the Radcliffe Observatory Magellanic Clouds catalog) is a candidate luminous blue variable located in the LH-41 OB association in the Large Magellanic Cloud. R85 has been shown to vary erratically in brightness with an amplitude of about 0.3 magnitudes.

R85 — main illustration
R85 — illustration

Key takeaways

  • R85 belongs to astronomy; place it in that map before memorising details.
  • Learn the definition first, then one example that makes the definition concrete.
  • Connect R85 to a quantity you can measure, compute or draw — that is where exam questions come from.
  • Reproduce the core statement of R85 from memory before moving on to harder problems.

Reference excerpt

R85 (or RMC 85, after the Radcliffe Observatory Magellanic Clouds catalog) is a candidate luminous blue variable located in the LH-41 OB association in the Large Magellanic Cloud.

R85 has been shown to vary erratically in brightness with an amplitude of about 0.3 magnitudes. It shows variations on several timescales, sometimes with a distinct 400 day period. It has also shown temperature changes associated with brightness changes over several years, a characteristic of luminous blue variables. Based on R85's current properties and evolutionary models, it probably started out with an initial mass of 28 M☉. It is theorized to be making a bubble known as DEM L132a with its stellar wind in the nebula LHA-120 N119, along with S Doradus. It has an infrared excess consistent with a stellar wind contribution.

References

Illustrations

R85 illustration
R85: A visual band light curve for R85, plotted from ASAS-SN data[11]
A visual band light curve for R85, plotted from ASAS-SN data[11]

Worked examples

Example 1 — a first encounter with R85

Start with the simplest possible case. Write down what R85 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 R85 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 R85 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 R85

In research
R85 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 R85 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
R85 is common in secondary-school and first-year university syllabi. It links to neighbouring topics Dorado, Durchmusterung objects, Henry Draper Catalogue objects, so understanding it makes those chapters shorter.
In everyday life
Look for R85 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 R85 in 20 minutes

  1. Read the reference excerpt below once, without taking notes.
  2. Close the page and write down what R85 means in your own words.
  3. Compare your version with the excerpt and mark what you missed.
  4. Work through the three examples above with pen and paper.
  5. Explain R85 out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is R85 in simple terms?

R85 (or RMC 85, after the Radcliffe Observatory Magellanic Clouds catalog) is a candidate luminous blue variable located in the LH-41 OB association in the Large Magellanic Cloud. R85 has been shown to vary erratically in brightness with an amplitude of about 0.3 magnitudes.

Why does R85 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 R85?

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 R85.

Tags

  • Dorado
  • Durchmusterung objects
  • Henry Draper Catalogue objects
  • Luminous blue variables
  • Stars in the Large Magellanic Cloud

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