astronomy

Pi1 Cygni

Pi1 Cygni 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 Pi1 Cygni rather than just read about it. In short: Pi1 Cygni, also named Azelfafage , is a star in the northern constellation of Cygnus. It is visible to the naked eye, having a combined apparent visual magnitude of 4.66.

Key takeaways

Pi1 Cygni belongs to astronomy; place it in that map before memorising details.
Learn the definition first, then one example that makes the definition concrete.
Connect Pi1 Cygni to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of Pi1 Cygni from memory before moving on to harder problems.

Reference excerpt

Pi1 Cygni, also named Azelfafage , is a star in the northern constellation of Cygnus. It is visible to the naked eye, having a combined apparent visual magnitude of 4.66. The distance to this system can be roughly gauged by its annual parallax shift of 1.89 mas, which yields a separation of around 1,700 light years from the Sun, give or take a hundred light years.

Nomenclature π1 Cygni (Latinised to Pi1 Cygni, abbreviated Pi1 Cyg, π1 Cyg) is the star's Bayer designation. The designations of the two components as Pi1 Cygni A and B derive from the convention used by the Washington Multiplicity Catalog (WMC) for multiple star systems, and adopted by the International Astronomical Union (IAU). It bore the traditional name Azelfafage, derived from the Arabic al-sulaḥfāh, the tortoise, originally a name for Lyra that was misattributed to a star in Cygnus. R. H. Allen's 1899 book Star Names incorrectly states that the name is derived from ظلف الفرس Dhilf al-faras meaning "the horse track" or (probably) ذيل الدجاجة Dhail al-dajājah meaning "the tail of the hen". In 2016, the IAU organized a Working Group on Star Names (WGSN) to catalogue and standardize proper names for stars. The WGSN approved the name Azelfafage for Pi1 Cygni on 12 September 2016 and it is now so included in the List of IAU-approved Star Names. In Chinese, 螣蛇 (Téng Shé), meaning Flying Serpent, refers to an asterism consisting of Pi1 Cygni, Alpha Lacertae, 4 Lacertae, Pi2 Cygni, HD 206267, Epsilon Cephei, Beta Lacertae, Sigma Cassiopeiae, Rho Cassiopeiae, Tau Cassiopeiae, AR Cassiopeiae, 9 Lacertae, 3 Andromedae, 7 Andromedae, 8 Andromedae, Lambda Andromedae, Kappa Andromedae, Psi Andromedae and Iota Andromedae. Consequently, the Chinese name for Pi1 Cygni itself is 螣蛇四 (Téng Shé sì, English: the Fourth Star of Flying Serpent).

Properties Pi1 Cygni has been described as a single-lined spectroscopic binary with a close, circular orbit, having a period of just 26.33 days. However, a 2020 paper finds no radial velocity variations on the timescale of the published orbit. The primary, visible, star is a somewhat evolved B-type subgiant star with a stellar classification of B3 IV. It has an estimated 10 times the mass of the Sun and around 5.6 times the Sun's radius. The star radiates 16,538 times the solar luminosity from its outer atmosphere at an effective temperature of roughly 18,360 K. It is about 25 million years old and is spinning with a projected rotational velocity of 55 km/s.

References

Illustrations

Worked examples

Example 1 — a first encounter with Pi1 Cygni

Start with the simplest possible case. Write down what Pi1 Cygni 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 Pi1 Cygni 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 Pi1 Cygni 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 Pi1 Cygni

In research: Pi1 Cygni 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 Pi1 Cygni 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: Pi1 Cygni is common in secondary-school and first-year university syllabi. It links to neighbouring topics B-type subgiants, Bayer objects, Bright Star Catalogue objects, so understanding it makes those chapters shorter.
In everyday life: Look for Pi1 Cygni 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.

Ask Teacher Smith questions about this articleOpens your AI tutor with a question about “Pi1 Cygni” →

Affiliate

Preply — study more efficiently by working with a personal tutor. 50% off.

How to study Pi1 Cygni in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what Pi1 Cygni 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 Pi1 Cygni out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is Pi1 Cygni in simple terms?

Pi1 Cygni, also named Azelfafage , is a star in the northern constellation of Cygnus. It is visible to the naked eye, having a combined apparent visual magnitude of 4.66.

Why does Pi1 Cygni 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 Pi1 Cygni?

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 Pi1 Cygni.