astronomy

HD 233731

HD 233731 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 HD 233731 rather than just read about it. In short: HD 233731, or HAT-P-22, is a suspected multiple star system in the northern circumpolar constellation of Ursa Major. It is invisible to the naked eye, having an apparent visual magnitude of 9.732.

Key takeaways

HD 233731 belongs to astronomy; place it in that map before memorising details.
Learn the definition first, then one example that makes the definition concrete.
Connect HD 233731 to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of HD 233731 from memory before moving on to harder problems.

Reference excerpt

HD 233731, or HAT-P-22, is a suspected multiple star system in the northern circumpolar constellation of Ursa Major. It is invisible to the naked eye, having an apparent visual magnitude of 9.732. This system is located at a distance of 267 light years from the Sun based on parallax, and is drifting further away with a radial velocity of +13 km/s. The stellar classification of the primary is G5V, matching an ordinary G-type main-sequence star. The star has a low level of stellar activity with an estimated age of 9 to 12 billion years old. Its metallicity is twice that of the Sun, unusual for its advanced age. HD 233731 has a similar mass and radius as the Sun, and is spinning with a rotation period of 28.7 days. It is radiating 77% of the luminosity of the Sun from its photosphere at an effective temperature of 5314 K. A faint stellar companion (2MASS J10224397+5007504) with a red hue is located at an angular separation of 9 arcseconds from the primary. In 2015, a spectroscopic stellar companion was reported with a semimajor axis of less than 33 AU. This star has an effective temperature of 4,000+250−400 K with a mass of 0.63+0.07−0.17 M☉.

Planetary system In 2010, a transiting hot Jupiter-like planet was detected, designated HAT-P-22b. It has an equilibrium temperature of 1,463±19 K, and planetary atmosphere is cloudy. The measurement of Rossiter-McLaughlin effect in 2018 has allowed to detect what the planetary orbit is well aligned with the equatorial plane of the star, with a misalignment angle equal to 25°±18°. In 2017, analysis of additional HARPS data showed a long-term trend that suggested the presence of an additional orbiting companion, HAT-P-22c.

References

Worked examples

Example 1 — a first encounter with HD 233731

Start with the simplest possible case. Write down what HD 233731 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 HD 233731 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 HD 233731 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 HD 233731

In research: HD 233731 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 HD 233731 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: HD 233731 is common in secondary-school and first-year university syllabi. It links to neighbouring topics G-type main-sequence stars, Henry Draper Catalogue objects, Planetary systems with one confirmed planet, so understanding it makes those chapters shorter.
In everyday life: Look for HD 233731 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 HD 233731 in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what HD 233731 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 HD 233731 out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is HD 233731 in simple terms?

HD 233731, or HAT-P-22, is a suspected multiple star system in the northern circumpolar constellation of Ursa Major. It is invisible to the naked eye, having an apparent visual magnitude of 9.732.

Why does HD 233731 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 HD 233731?

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 HD 233731.