astronomy

Hiroki Kosai

Hiroki Kosai 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 Hiroki Kosai rather than just read about it. In short: Hiroki Kosai (香西洋樹, Kōsai Hiroki; 8 February 1933 – 26 March 2026) was a Japanese astronomer with the Kiso Observatory. He is best known for helping to popularize astronomy in Japan and for his observations of comets and asteroids, most notably with his co-discovery of the comet 1976 XVI.

Key takeaways

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

Reference excerpt

Hiroki Kosai (香西洋樹, Kōsai Hiroki; 8 February 1933 – 26 March 2026) was a Japanese astronomer with the Kiso Observatory. He is best known for helping to popularize astronomy in Japan and for his observations of comets and asteroids, most notably with his co-discovery of the comet 1976 XVI. He is credited by the Minor Planet Center (MPC) with the discovery of nearly 100 asteroids. Kosai died on 26 March 2026, at the age of 93.

Awards and honors Asteroid 3370 Kohsai, discovered by Karl Reinmuth at Heidelberg Observatory in 1930, is named in his honor. The official naming citation was published by the MPC on 14 April 1987 (M.P.C. 11750).

List of discovered minor planets

Hiroki Kosai discovered several asteroids, all in collaboration with A Kiichirō Furukawa and B Goro Sasaki:

See also List of minor planet discoverers § H. Kosai

References

External links Activities of Asteroid Studies by Amateur Astronomers in Japan 2008 Great Meeting at Nikon Headquarters

Worked examples

Example 1 — a first encounter with Hiroki Kosai

Start with the simplest possible case. Write down what Hiroki Kosai 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 Hiroki Kosai 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 Hiroki Kosai 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 Hiroki Kosai

In research: Hiroki Kosai 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 Hiroki Kosai 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: Hiroki Kosai is common in secondary-school and first-year university syllabi. It links to neighbouring topics 1933 births, 2026 deaths, 20th-century Japanese astronomers, so understanding it makes those chapters shorter.
In everyday life: Look for Hiroki Kosai 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 Hiroki Kosai in 20 minutes

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

Frequently asked questions

What is Hiroki Kosai in simple terms?

Why does Hiroki Kosai 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 Hiroki Kosai?

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 Hiroki Kosai.