astronomy

HD 100655

HD 100655 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 100655 rather than just read about it. In short: HD 100655, also named Formosa, is a star in the zodiac constellation of Leo, located 451 light-years away from the Sun. It has an apparent visual magnitude of +6.45, which makes it a challenge to see with the naked eye under ideal viewing conditions.

Key takeaways

HD 100655 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 100655 to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of HD 100655 from memory before moving on to harder problems.

Reference excerpt

HD 100655, also named Formosa, is a star in the zodiac constellation of Leo, located 451 light-years away from the Sun. It has an apparent visual magnitude of +6.45, which makes it a challenge to see with the naked eye under ideal viewing conditions. The star is moving closer to the Earth with a heliocentric radial velocity of −5 km/s. It has one confirmed planet. HD 100655 is an evolved giant star with a stellar classification of G9 III. It is a red clump giant, which means it is currently on the horizontal branch and is generating energy through helium fusion at its core. This star is around 900 million years old with 2.2 times the mass of the Sun and has expanded to 8.8 times the Sun's radius. It is radiating 4,918 times the Sun's luminosity from its enlarged photosphere at an effective temperature of 4,918 K.

Naming The star HD 100655 is named Formosa. The name was selected in the NameExoWorlds campaign by Taiwan, during the 100th anniversary of the IAU. Formosa is the historical name of Taiwan used in the 17th century, meaning 'beautiful' in Portuguese. The planet HD 100655 b is named Sazum, after the township Yuchi and it means 'water' in the Thao language.

Planetary system The planetary companion, announced in 2011, was discovered by a Korean–Japanese planet search program by the radial velocity method. The motions of the host star displayed Keplerian variation, indicating a perturbing body in orbit. The best fit model suggests a body having a minimum mass of 1.7 MJ and showing a 158-day orbital period with a semimajor axis of 0.76 astronomical units (114 Gm) and a low eccentricity of 0.085. This is one of the two least massive planets known around clump giants, as of 2012.

Illustrations

Worked examples

Example 1 — a first encounter with HD 100655

Start with the simplest possible case. Write down what HD 100655 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 100655 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 100655 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 100655

In research: HD 100655 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 100655 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 100655 is common in secondary-school and first-year university syllabi. It links to neighbouring topics Bright Star Catalogue objects, Durchmusterung objects, G-type giants, so understanding it makes those chapters shorter.
In everyday life: Look for HD 100655 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 100655 in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what HD 100655 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 100655 out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is HD 100655 in simple terms?

Why does HD 100655 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 100655?

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 100655.