astronomy

Tau Persei

Tau 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 Tau Persei rather than just read about it. In short: Tau Persei (τ Per), also known as 18 Persei, is a binary star in the constellation of Perseus. The system is fairly close, and is located about 254 light-years (78 parsecs) away, based on its parallax.

Key takeaways

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

Reference excerpt

Tau Persei (τ Per), also known as 18 Persei, is a binary star in the constellation of Perseus. The system is fairly close, and is located about 254 light-years (78 parsecs) away, based on its parallax.

Tau Persei is an eclipsing binary, which means the two stellar components orbit each other in such an orientation that they periodically eclipse each other, while blocking the other's light. Unlike many eclipsing binaries that have short orbital periods, Tau Persei has an orbital period of 4.15 years. With a semi-major axis of 0.055 arcseconds, this is one of the few eclipsing binaries whose components can be resolved with interferometry. The primary component of Tau Persei is a red giant with a spectral type of G8III. It has a radius 16 times that of the Sun, and is about 390 million years old. Its companion is an A-type main-sequence star. In 1989, the primary star eclipsed the secondary, allowing for the stellar parameters to be derived via its light curve.

Naming In Chinese, 大陵 (Dà Líng), meaning Mausoleum, refers to an asterism consisting of τ Persei, 9 Persei, ι Persei, κ Persei, β Persei, ρ Persei, 16 Persei and 12 Persei. Consequently, the Chinese name for τ Persei itself is 大陵二 (Dà Líng èr, English: the Second Star of Mausoleum.).

References

Illustrations

Worked examples

Example 1 — a first encounter with Tau Persei

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

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

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

Frequently asked questions

What is Tau Persei in simple terms?

Why does Tau 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 Tau 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 Tau Persei.