astronomy

XX Persei

XX 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 XX Persei rather than just read about it. In short: XX Persei (IRC +50052 / HIP 9582 / BD+54°444) is a semiregular variable red supergiant star in the constellation Perseus, between the Double Cluster and the border with Andromeda. Variability In 1917 it was announced that Ida E.

Key takeaways

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

Reference excerpt

XX Persei (IRC +50052 / HIP 9582 / BD+54°444) is a semiregular variable red supergiant star in the constellation Perseus, between the Double Cluster and the border with Andromeda.

Variability

In 1917 it was announced that Ida E. Woods had discovered that this star is a variable star, by examining 520 photographs taken from December 1, 1887 through February 4, 1913. It was given its variable star designation in 1921. XX Persei is a semiregular variable star of sub-type SRc, indicating a cool supergiant. The General Catalogue of Variable Stars gives the period as 415 days. It also shows a long secondary period which was originally given at 4,100 days. A more recent study shows only slow variations with a period of 3,150 ± 1,000 days. Another study failed to find any long period up to 10,000 days.

Distance The most likely distance of XX Per is 2,290 pc, from assumed membership of the Perseus OB1 association. Gaia Data Release 3 includes a parallax of 0.3980±0.0316 mas, corresponding to a distance of around 2,500 pc.

Characteristics XX Per is a red supergiant of spectral type M4Ib with an effective temperature below 4,000 K. It has a large infrared excess, indicating surrounding dust at a temperature of 900 K, but no masers have been detected. XX Persei has a mass of 16 solar masses, above the limit beyond which stars end their lives as supernovae. This makes XX Persei similar to the more well-known red supergiant Antares.

Companions XX Persei is listed in multiple star catalogues with a companion of magnitude 9.8 223″ away. This star is BD+54°445 and it is an unrelated foreground object. In addition, the spectrum of XX Persei shows absorption lines of a hot companion too close to be resolved. The combined spectral type has been given as M4Ib + B7V, while the UV spectrum of the companion has been used to derive a spectral classification of A.

Illustrations

Worked examples

Example 1 — a first encounter with XX Persei

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

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

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

Frequently asked questions

What is XX Persei in simple terms?

XX Persei (IRC +50052 / HIP 9582 / BD+54°444) is a semiregular variable red supergiant star in the constellation Perseus, between the Double Cluster and the border with Andromeda. Variability In 1917 it was announced that Ida E.

Why does XX 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 XX 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 XX Persei.