astronomy

RW Persei

RW Persei 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 RW Persei rather than just read about it. In short: RW Persei is a eclipsing binary star system in the northern constellation of Perseus. It has a peak apparent visual magnitude of 9.68, so this system is too faint to be viewed with the naked eye.

Key takeaways

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

Reference excerpt

RW Persei is a eclipsing binary star system in the northern constellation of Perseus. It has a peak apparent visual magnitude of 9.68, so this system is too faint to be viewed with the naked eye. During the primary eclipse the brightness decreases to magnitude 11.36, but only to magnitude 9.78 with the secondary eclipse. The distance to RW Persei is approximately 1,510 light years, based on parallax measurements. It is receding from the Sun with a radial velocity of 5.8±2.7 km/s.

Observations The variability of this star was discovered by Sigurd Enebo, for which he received the 1906 Lindemann Award from the Astronomische Gesellschaft. He classified it as an Algol variable and found a period of 13.196 days. Enebo refined the period to 13.1989 days in 1910. The low brightness and relatively long period of this system meant that it received little study for many decades. In 1945, O. Struve found emission lines, but (except for the H-alpha emission lines) only during an eclipse. It has a deep primary eclipse with only a minor secondary eclipse. He interpreted the emission as a nebulous stream moving with the eclipsed star. D. S. Hall noted a rapid decrease in the duration of the primary eclipse in 1967, becoming a partial eclipse. Observations made in 1974 suggested a possible period change in the eclipse cycle. In 1986, J. J. Dobias and M. J. Plavec determined the primary component to be a Be star with an optically thick accretion disk in orbit. The secondary is an ordinary K2 giant star. Subsequent observations in 1988 and 1989 failed to confirm this disk, although they did show that the primary component must be spinning at 30 times the rate of synchronous rotation. In 1991, the eclipse amplitude was found to have changed multiple times, declining from a magnitude difference of 3.20 in 1900 down to 1.75 in blue light. This is the second system shown to undergo such large adjustments in eclipse amplitude after IU Aurigae. The changes suggested a wobble in the orbital plane caused by an orbiting third body in the system. Alterations in the O–C diagram supported this interpretation, giving an orbital period of 68 years for the third body. However, a photometric study in 1992 failed to confirm the presence of a third body in the system. Instead, it was proposed that changes in the polar radius of the primary, brought on by accretion and slowed rotation, may explain the variations.

References

Illustrations

Worked examples

Example 1 — a first encounter with RW Persei

Start with the simplest possible case. Write down what RW Persei 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 RW Persei 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 RW Persei 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 RW Persei

In research: RW Persei 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 RW Persei 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: RW Persei is common in secondary-school and first-year university syllabi. It links to neighbouring topics Algol variables, Be stars, Durchmusterung objects, so understanding it makes those chapters shorter.
In everyday life: Look for RW Persei 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 RW Persei in 20 minutes

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

Frequently asked questions

What is RW Persei in simple terms?

RW Persei is a eclipsing binary star system in the northern constellation of Perseus. It has a peak apparent visual magnitude of 9.68, so this system is too faint to be viewed with the naked eye.

Why does RW Persei 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 RW Persei?

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 RW Persei.