astronomy

Mira B

Mira B 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 Mira B rather than just read about it. In short: Mira B (also known as VZ Ceti) is a white dwarf and the companion star to the variable star Mira. The two are separated by around 100 AU.

Key takeaways

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

Reference excerpt

Mira B (also known as VZ Ceti) is a white dwarf and the companion star to the variable star Mira. The two are separated by around 100 AU. Suspected as early as 1918, it was visually confirmed in 1923 by Robert Grant Aitken, and has been observed more or less continually since then, most recently by the Chandra X-Ray Observatory. Long known to be erratically variable itself, its fluctuations seem to be related to its accretion of matter from Mira's stellar wind, which makes it a symbiotic star.

Orbit The exact orbit around Mira is poorly known due to its long period, though a commonly cited estimate of 497.9 years was published by Prieur et al in 2002. One 2018 study by Snaid et al. finds a reasonable fit with an orbital period of 945 years, an angular semi-major axis of 1.03" and a circular orbit. The distance in the Hipparcos catalog, together with the angular semi-major axis, give a physical semi-major axis of 95 AU.

Physical properties

In January 2007, astronomers at the Keck Observatory announced the discovery of a protoplanetary disk around Mira B. Discovered via infrared data, the disk is apparently derived from captured material from Mira itself; Mira B accretes as much as one percent of the matter lost by its primary. Though planetary formation is perhaps unlikely as long as the disk is in active accretion, it may proceed apace once Mira A completes its red giant phase and becomes a white dwarf. Mira B was long suspected to itself be a white dwarf. Several factors, such as its low x-ray luminosity, suggested that Mira B could instead be a normal main-sequence star of spectral type K and with a mass of roughly 0.7 M☉. However, a 2010 analysis of rapid optical brightness variations indicated that Mira B is, in fact, a white dwarf. Although most white dwarfs have masses close to 0.6 M☉, and Mira B has been assumed to have it too, measurements published in 2026, based on its accretion rate, suggest a mass of either 0.24±0.04 M☉ in the case of accretion through overflow of the red giant's Roche lobe by its stellar wind, or 0.42±0.04 M☉ in the case of Bondi–Hoyle–Lyttleton accretion. Mass-radius relations give radii of 0.020 or 0.015 R☉, respectively. The case of wind roche lobe overflow is more probable, so Mira B is likely an extremely low-mass white dwarf.

External links From the AAVSO Variable Star of the Month: Mira Archived 2003-07-05 at the Wayback Machine Sixth Orbit Catalog Chandra Photo Album, Mira press release Born Again Protoplanetary Disk Around Mira B

References

Illustrations

Worked examples

Example 1 — a first encounter with Mira B

Start with the simplest possible case. Write down what Mira B 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 Mira B 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 Mira B 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 Mira B

In research: Mira B 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 Mira B 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: Mira B is common in secondary-school and first-year university syllabi. It links to neighbouring topics Astronomical objects discovered in 1923, Bayer objects, Binary stars, so understanding it makes those chapters shorter.
In everyday life: Look for Mira B 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 “Mira B” →

Affiliate

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

How to study Mira B in 20 minutes

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

Frequently asked questions

What is Mira B in simple terms?

Mira B (also known as VZ Ceti) is a white dwarf and the companion star to the variable star Mira. The two are separated by around 100 AU.

Why does Mira B 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 Mira B?

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 Mira B.