astronomy

Pi Mensae b

Pi Mensae 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 Pi Mensae b rather than just read about it. In short: Pi Mensae b (π Men b, π Mensae b), also known as HD 39091 b, is an extrasolar planet approximately 60 light-years away in the constellation of Mensa. The planet was announced orbiting the yellow main-sequence star Pi Mensae in October 2001.

Key takeaways

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

Reference excerpt

Pi Mensae b (π Men b, π Mensae b), also known as HD 39091 b, is an extrasolar planet approximately 60 light-years away in the constellation of Mensa. The planet was announced orbiting the yellow main-sequence star Pi Mensae in October 2001.

Detection and discovery On October 15, 2001, a team of astronomers including Jones, Butler, Tinney, Marcy, Penny, McCarthy, Carter, and Pourbaix announced the discovery of one of the most massive extrasolar planets that have yet been observed. It was discovered by the Anglo-Australian Planet Search team, using a Doppler spectrometer mounted on the Anglo-Australian Telescope.

Physical characteristics Pi Mensae b has a very eccentric orbit and takes 5.72 years to revolve around the star. The semi-major axis of the planet's orbit around the star is 3.31 AU. This planet passes through the star's habitable zone at periastron (1.19 AU) while at apastron, it passes to around Jupiter-Sun distance (5.44 AU). The gravitational influence of this planet would disrupt the orbit of any potentially Earth-like planet. Pi Mensae b is over ten times more massive than Jupiter, the most massive planet in the Solar System. In 2020, the true mass of Pi Mensae b was measured to be 14.1 MJ via astrometry. Since this is greater than 13 Jupiter masses, the object could be considered a brown dwarf. The most recent astrometric results as of 2022 have revised this mass estimate slightly downward, to 12.33 MJ. The plane of orbit of Pi Mensae b is strongly inclined to equatorial plane of the star, with the misalignment equal to 24±4.1°.

See also 30 Arietis Bb Gliese 777 b HD 70642 b

References

External links "HD 39091". Exoplanets. Archived from the original on 2009-11-25. Retrieved 2008-07-28. "Pi Mensae". SolStation. Archived from the original on June 16, 2002. Retrieved 2008-07-28. "Pi Mensae". Планетные Системы (in Russian). Retrieved 2008-07-28. Hatzes, Artie P.; et al. (2022). "A Radial Velocity Study of the Planetary System of π Mensae: Improved Planet Parameters for π Mensae c and a Third Planet on a 125 Day Orbit". The Astronomical Journal. 163 (5): 223. arXiv:2203.01018. Bibcode:2022AJ....163..223H. doi:10.3847/1538-3881/ac5dcb. S2CID 247218413.

Worked examples

Example 1 — a first encounter with Pi Mensae b

Start with the simplest possible case. Write down what Pi Mensae 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 Pi Mensae 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 Pi Mensae 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 Pi Mensae b

In research: Pi Mensae 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 Pi Mensae 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: Pi Mensae b is common in secondary-school and first-year university syllabi. It links to neighbouring topics Brown dwarfs, Exoplanets detected by astrometry, Exoplanets detected by radial velocity, so understanding it makes those chapters shorter.
In everyday life: Look for Pi Mensae 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.

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How to study Pi Mensae b in 20 minutes

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

Frequently asked questions

What is Pi Mensae b in simple terms?

Why does Pi Mensae 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 Pi Mensae 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 Pi Mensae b.