astronomy

HD 90362

HD 90362 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 90362 rather than just read about it. In short: HD 90362 (HR 4092; 47 G. Sextantis) is a solitary star located in the equatorial constellation of Sextans.

Key takeaways

HD 90362 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 90362 to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of HD 90362 from memory before moving on to harder problems.

Reference excerpt

HD 90362 (HR 4092; 47 G. Sextantis) is a solitary star located in the equatorial constellation of Sextans. It is faintly visible to the naked eye as a redish-orange-hued point of light with an apparent magnitude of 5.56. Gaia DR3 parallax measurements imply a distance of approximately 460 light-years and it is receding with a heliocentric radial velocity of 35.6 km/s. At its current distance, HD 90362's brightness is diminished by an interstellar extinction of 0.19 magnitudes and it has an absolute magnitude of +0.19. HD 90362 is an old population II star with a stellar classification of K6 III Fe −0.5, indicating that it is an evolved K-type giant that has exhausted hydrogen at its core and left the main sequence along with a mild spectral underabundance of iron. It is currently on the asymptotic giant branch, generating energy via the fusion of hydrogen and helium shells around an inert carbon core. It has only 44% the mass of the Sun but at the age of 11 billion years, it has expanded to 41.1 times the radius of the Sun. It radiates 252 times the luminosity of the Sun from its enlarged photosphere at an effective temperature of 3,804 K. HD 90362 is metal deficient with an iron abundance of [Fe/H] = −0.1 or 79.4% of the Sun's and it spins slowly with a projected rotational velocity of approximately 1.5 km/s. The variability of the star was first detected in 1997 by the Hipparcos mission. It found variations between 5.69 and 5.72 in the Hipparcos passband. As of 2004, its variability has not been confirmed. HD 90362 has an optical companion located 142.6" away along a position angle of 100° as of 2010. It was first observed by M. Scaria in 1981.

References

Illustrations

Worked examples

Example 1 — a first encounter with HD 90362

Start with the simplest possible case. Write down what HD 90362 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 90362 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 90362 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 90362

In research: HD 90362 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 90362 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 90362 is common in secondary-school and first-year university syllabi. It links to neighbouring topics Asymptotic-giant-branch stars, Bright Star Catalogue objects, Double stars, so understanding it makes those chapters shorter.
In everyday life: Look for HD 90362 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 90362 in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what HD 90362 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 90362 out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is HD 90362 in simple terms?

HD 90362 (HR 4092; 47 G. Sextantis) is a solitary star located in the equatorial constellation of Sextans.

Why does HD 90362 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 90362?

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 90362.