astronomy

HD 90089

HD 90089 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 90089 rather than just read about it. In short: HD 90089 (HR 4084; Gliese 392.1) is a star system located in the northern circumpolar constellation Camelopardalis. With a combined apparent magnitude of 5.25, it is faintly visible to the naked eye under ideal conditions.

Key takeaways

HD 90089 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 90089 to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of HD 90089 from memory before moving on to harder problems.

Reference excerpt

HD 90089 (HR 4084; Gliese 392.1) is a star system located in the northern circumpolar constellation Camelopardalis. With a combined apparent magnitude of 5.25, it is faintly visible to the naked eye under ideal conditions. This star is located relatively close at a distance of 75 light years, but is drifting away at a rate of almost 8 km/s.

Characteristics The two innermost components form an astrometric binary system, initially indicated through Gaia astrometry, and validated in 2026 with the direct detection of the secondary component. The observed separation was of 0.024" along a position angle of 182.4°. The main component of HD 90089, component Aa, is an F4 main-sequence star with the calcium K-line and metallic lines of an F2 star. Although the spectral type is of a form that would indicate an Am star, it is not listed in any of the major catalogues of chemically peculiar stars. The secondary, component Ab, is only 0.45 magnitudes fainter than the primary at infrared wavelengths. An infrared excess has been detected around the inner system, most likely indicating the presence of a circumstellar disk at a radius of 145 AU. The temperature of this dust is 30 K. In addition to the inner pair, there is an M0 companion separated by 14.1" from the inner pair. It was confirmed to be a physical companion in 2018, and is named component B.

References

External links HR 4084 Image HD 90089

Illustrations

Worked examples

Example 1 — a first encounter with HD 90089

Start with the simplest possible case. Write down what HD 90089 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 90089 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 90089 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 90089

In research: HD 90089 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 90089 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 90089 is common in secondary-school and first-year university syllabi. It links to neighbouring topics Am stars, Bright Star Catalogue objects, Camelopardalis, so understanding it makes those chapters shorter.
In everyday life: Look for HD 90089 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 90089 in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what HD 90089 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 90089 out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is HD 90089 in simple terms?

Why does HD 90089 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 90089?

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 90089.