astronomy

V389 Cygni

V389 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 V389 Cygni rather than just read about it. In short: V389 Cygni, also known as HD 201433 and HR 8094, is a multiple star system about 390 light years from the Earth, in the constellation Cygnus. It is visible as a 5th-magnitude star, making it faintly visible to the naked eye of an observer far from city lights.

Key takeaways

V389 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 V389 Cygni to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of V389 Cygni from memory before moving on to harder problems.

Reference excerpt

V389 Cygni, also known as HD 201433 and HR 8094, is a multiple star system about 390 light years from the Earth, in the constellation Cygnus. It is visible as a 5th-magnitude star, making it faintly visible to the naked eye of an observer far from city lights. One component of that system is a slowly pulsating B-type star (SPB) causing the system's brightness to vary from magnitude 5.55 to 5.71 over a period of 1.4 days. V389 Cygni is catalogued as a multiple star with four visible components. The faint companions TYC 2701-897-1 and UCAC4 602-123109 are unrelated background objects, at 59″ and 73″ respectively. A 5th-magnitude and 8th-magnitude star separated by 3.3″ form a common proper motion pair, generally referred to as components A and B). The brighter star, component A, is a spectroscopic binary and the system also harbours an unseen third star, making it a triple and the system as a whole then includes four stars. Both the visible stars are chemically peculiar, A being an Ap star and B an Am star. The blended spectral class of the pair is B9V, with the brighter star having a class of B9VspSi (or B9 Si Mg) and the fainter kA2.5hA7VmA9n. Component A of V389 Cygni was discovered to be a spectroscopic binary from spectra obtained in 1918. In 1921, Reynold K. Young of the Dominion Astrophysical Observatory derived its orbit from 49 additional spectra obtained in 1920-1921. He found it to have a circular orbit, with a period of 3.3137 days. He noted that the star showed evidence of variability.

In 1922 Kurt Bottlinger and Paul Guthnick detected variability in V389 Cygni. Between 1936 and 1942, Guthnick made extensive photoelectric observations of V389 Cygni. He found that sometimes the brightness appeared to change irregularly, and at other times two periods, 1.12912 and 1.19328 days, could be seen. Neither period was related to the orbital period of the spectroscopic binary. Guthnick postulated that the system consisted of two Cepheid variables orbiting each other, but it is now believed that only one of the stars in the close binary pair is variable, and it is an SPB star. In 1978, Frank Gieseking and Wilhelm Seggewiss refined Young's orbit determination for the spectroscopic binary (new period 3.313168±0.000008 days), and found that V389 Cygni is a triple star. The third, unseen component, orbits the close binary pair with a period of 154.09±0.02 days. They were unable to derive a nonzero eccentricity for either orbit. In 1989, David Barlow re-analyzed earlier data and found that while the orbit of the inner binary appeared to be circular, the data were best fit if the orbit of the third star had an eccentricity of 0.311±0.057. In 2017, Thomas Kallinger et al. published an extensive spectroscopic and astroseismic study of V389 Cygni. They found 29 pulsation frequencies in the BRITE satellite data for the star. They were able to derive an eccentricity value for the inner binary pair's orbit of 0.015±0.003. Their astroseismic results indicate that the outer layer of the SPB star is in the process of becoming tidally locked to its close companion, but the inner portion of the star still rotates at a significantly different speed.

References

Illustrations

Worked examples

Example 1 — a first encounter with V389 Cygni

Start with the simplest possible case. Write down what V389 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 V389 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 V389 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 V389 Cygni

In research: V389 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 V389 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: V389 Cygni is common in secondary-school and first-year university syllabi. It links to neighbouring topics Am stars, Ap stars, Bright Star Catalogue objects, so understanding it makes those chapters shorter.
In everyday life: Look for V389 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.

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How to study V389 Cygni in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what V389 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 V389 Cygni out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is V389 Cygni in simple terms?

Why does V389 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 V389 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 V389 Cygni.