astronomy

RV Tauri

RV Tauri 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 RV Tauri rather than just read about it. In short: RV Tauri (RV Tau) is a star in the constellation Taurus. It is a yellow supergiant and is the prototype of a class of pulsating variables known as RV Tauri variables.

Key takeaways

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

Reference excerpt

RV Tauri (RV Tau) is a star in the constellation Taurus. It is a yellow supergiant and is the prototype of a class of pulsating variables known as RV Tauri variables. It is a post-AGB star and a spectroscopic binary about 4,700 light years away.

Variability RV Tau was discovered to be variable in 1905 by Lydia Ceraski, and by 1907 it was clear that it had minima of alternating brightness. Over a period of 78.5 days it shows two maxima at around magnitude 9.5, a minimum around magnitude 10.0, and another minimum about 0.5 magnitudes fainter. This change in brightness is caused by pulsations: the temperature and radius vary, causing some variation in luminosity but mostly a shift of the emitted radiation from visual to infrared. The spectral type varies in line with the temperature, being classified as G2 at its brightest and M2 at its dimmest. In addition to the fundamental period given, RV Tauri also shows variations in its mean brightness over a period of about 1,200 days, a characteristic which defines the subclass RVb. The maxima and minima in each period vary by several tenths of a magnitude with no obvious regularity.

Binary system RV Tauri is a single-lined spectroscopic binary. The period of 1,198 days corresponds to the long-term variations in the mean brightness of the system. These are caused by changing obscuration of the primary star by a circumstellar disc. The companion is thought to be more massive than the variable primary star, but it cannot be detected in the spectrum and it is likely to be a red dwarf. The disc surrounds both stars at a distance of about five astronomical units (AU). The stars themselves have an eccentric orbit and their separation varies between about 0.75 and 2.25 AU.

Visibility RV Tau is well placed for northern hemisphere observers during the winter months, and observations can be made from August to April. However it is faint, located in a nondescript patch of sky between the Pleiades and Beta Aurigae.

Properties The distance to RV Tau has been calculated by various methods, including modelling the atmosphere. RV Tauri stars have been shown to follow a period-luminosity relationship, and this can be used to confirm the luminosity and distance. They have low masses, but are extended cool stars of high luminosity undergoing strong mass loss. RV Tau has a luminosity of 2,800 L☉ but a spectral luminosity class of bright supergiant (Ia), indicating the rarified nature of its atmosphere. Its temperature varies as it pulsates, between about 4,225 K and 5,080 K. Surface abundances show enhancement of some heavy elements, fusion products thought to have been dredged up during an earlier AGB phase. Carbon in particular is strongly in excess in RV Tau. However, its overall metallicity is lower than the Sun's.

Evolution RV Tau is likely a post-asymptotic giant branch (AGB) star, an originally sun-like star which is in the end stages of its life just prior to the expulsion of a planetary nebula and contraction to a white dwarf. RV Tau gives an insight into the lives and deaths of stars like the Sun. Evolution models show it takes about 10 billion years for a 1 solar mass (1 M☉) star to reach the Asymptotic Giant Branch.

References

External links

RV Tauri on WikiSky: DSS2, SDSS, GALEX, IRAS, Hydrogen α, X-Ray, Astrophoto, Sky Map, Articles and images AAVSO observations of RV Tauri RV Tauri — The strange prototype of a strange class

Illustrations

Worked examples

Example 1 — a first encounter with RV Tauri

Start with the simplest possible case. Write down what RV Tauri 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 RV Tauri 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 RV Tauri 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 RV Tauri

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

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

Frequently asked questions

What is RV Tauri in simple terms?

RV Tauri (RV Tau) is a star in the constellation Taurus. It is a yellow supergiant and is the prototype of a class of pulsating variables known as RV Tauri variables.

Why does RV Tauri 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 RV Tauri?

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 RV Tauri.