astronomy

HW Virginis

HW Virginis 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 HW Virginis rather than just read about it. In short: HW Virginis, abbreviated HW Vir, is an eclipsing binary system (of the Algol type), approximately 563 light-years away based on the parallax measured by the Gaia spacecraft, in the constellation of Virgo. The system comprises an eclipsing B-type subdwarf star and red dwarf star.

Key takeaways

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

Reference excerpt

HW Virginis, abbreviated HW Vir, is an eclipsing binary system (of the Algol type), approximately 563 light-years away based on the parallax measured by the Gaia spacecraft, in the constellation of Virgo. The system comprises an eclipsing B-type subdwarf star and red dwarf star. The two stars orbit each other every 0.116795 days. John William Menzies and Freddy Marang announced their discovery of the eclipsing binary nature of this star in 1985.

Eclipse timing variations

Based on variations in the timing of the system's eclipses, in 2008 it was claimed that two giant planets were in orbit around the binary, with masses of 8.47 and 19.2 times the mass of Jupiter orbiting with periods of 9.1 and 15.8 years respectively. The proposed system was later shown to be extremely unstable, with mean lifetimes less than 1000 years in the parameter space allowed by the uncertainties in the data. An alternate, dynamically-stable orbital solution was proposed with a 14.3 Jupiter mass object on a 12-year orbit and an outer companion of 65 Jupiter masses on a 55-year orbit, however it has been noted that the outer companion's orbital parameters are highly unconstrained, again casting doubt on the reality of this model. The problems with modelling this system and the proposed planets orbiting several other post-common envelope binaries has led to the suggestion that the eclipse timing variations used to infer the existence of planets has a non-planetary origin. The eclipse timing variations of HW Virginis were shown to be incompatible with all previous planetary system models as of 2018, and again in 2021. However, eclipse timing variations cannot be explained by known stellar mechanisms either. There is tentative evidence for the presence of a planet from astrometric measurements, with future data releases of the Gaia spacecraft being predicted to be able to fully confirm this.

See also Algol – Eclipsing variable star in the constellation Perseus CM Draconis – Star in the constellation Draco QS Virginis – Eclipsing binary star in the constellation Virgo NN Serpentis – Eclipsing post-common envelope binary star system in the constellation Serpens List of extrasolar planets

References

External links "Notes for star HW Vir". Extrasolar Planets Encyclopaedia. Archived from the original on December 22, 2008. Retrieved 25 November 2008.

Illustrations

Worked examples

Example 1 — a first encounter with HW Virginis

Start with the simplest possible case. Write down what HW Virginis 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 HW Virginis 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 HW Virginis 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 HW Virginis

In research: HW Virginis 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 HW Virginis 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: HW Virginis is common in secondary-school and first-year university syllabi. It links to neighbouring topics Algol variables, B-type subdwarfs, Durchmusterung objects, so understanding it makes those chapters shorter.
In everyday life: Look for HW Virginis 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 HW Virginis in 20 minutes

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

Frequently asked questions

What is HW Virginis in simple terms?

Why does HW Virginis 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 HW Virginis?

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 HW Virginis.