astronomy

G 99-47

G 99-47 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 G 99-47 rather than just read about it. In short: G 99-47 (V1201 Orionis, EGGR 290) is a nearby degenerate star (white dwarf) of spectral class DAP8 (DAP8.9, or DAP8.7), the single known component of the system, located in the constellation Orion. G 99-47 is the 10th-closest known white dwarf, the next closest after LP 658-2 and GJ 3991 B.

Key takeaways

G 99-47 belongs to astronomy; place it in that map before memorising details.
Learn the definition first, then one example that makes the definition concrete.
Connect G 99-47 to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of G 99-47 from memory before moving on to harder problems.

Reference excerpt

G 99-47 (V1201 Orionis, EGGR 290) is a nearby degenerate star (white dwarf) of spectral class DAP8 (DAP8.9, or DAP8.7), the single known component of the system, located in the constellation Orion. G 99-47 is the 10th-closest known white dwarf, the next closest after LP 658-2 and GJ 3991 B. The mass of G 99-47 is 0.71±0.03 Solar masses; its surface gravity is 108.20 ± 0.05 (1.58 · 108) cm·s−2, or approximately 162 000 of Earth's, corresponding to a radius 7711 km, or 121% of Earth's. Its temperature is 5790 ± 110 K, almost like the Sun's; its cooling age, i. e. age as degenerate star (not including lifetime as main sequence star and as giant star) is 3.97 Gyr. Due almost equal to the Sun's temperature, GJ 1087 should appear almost the same white color as the Sun. The white dwarf has a strong magnetic field, with measured vertical component near surface equal to 560 T.

Close approach to the Sun In about 19,000 years, G 99-47 will have its closest approach to the Sun at a distance of about 2.5 light years.

See also List of star systems within 25–30 light-years

Notes

References

Illustrations

Worked examples

Example 1 — a first encounter with G 99-47

Start with the simplest possible case. Write down what G 99-47 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 G 99-47 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 G 99-47 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 G 99-47

In research: G 99-47 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 G 99-47 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: G 99-47 is common in secondary-school and first-year university syllabi. It links to neighbouring topics Gliese and GJ objects, Objects with variable star designations, Orion (constellation), so understanding it makes those chapters shorter.
In everyday life: Look for G 99-47 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 G 99-47 in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what G 99-47 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 G 99-47 out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is G 99-47 in simple terms?

Why does G 99-47 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 G 99-47?

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 G 99-47.