astronomy

Gliese 686

Gliese 686 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 Gliese 686 rather than just read about it. In short: Gliese 686 (GJ 686 / HIP 86287 / LHS 452) is a star in the constellation of Hercules, with an apparent magnitude +9.577. Although it is close to the Solar System – at 26.6 light-years – it is not the closest known star in its constellation, since Gliese 661 is 20.9 light years away.

Key takeaways

Gliese 686 belongs to astronomy; place it in that map before memorising details.
Learn the definition first, then one example that makes the definition concrete.
Connect Gliese 686 to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of Gliese 686 from memory before moving on to harder problems.

Reference excerpt

Gliese 686 (GJ 686 / HIP 86287 / LHS 452) is a star in the constellation of Hercules, with an apparent magnitude +9.577. Although it is close to the Solar System – at 26.6 light-years – it is not the closest known star in its constellation, since Gliese 661 is 20.9 light years away. The closest system to this star is the bright μ Herculis, at 4.5 light years. They are followed by GJ 1230 and Gliese 673, at 7.2 and 7.6 light years respectively. Gliese 686 is one of the many red dwarfs in the Solar System neighborhood with a spectral type of M1V, and has an effective temperature of about 3600 K. Its brightness in the visible spectrum is equal to 0.82% of that of the Sun, while its total luminosity is equivalent to 2.7% that of the Sun, since a significant amount of the radiation emitted by these stars is infrared invisible light. Considering only this last parameter, Gliese 686 is considerably brighter than other known red dwarfs: it is 6.5 times more luminous than Ross 154 and 15 times more than Proxima Centauri, the closest star to the Solar System. Gliese 686 has a radius approximately half that of the Sun. Its projected rotation speed is 2.5 km / s, its rotation period being equal to or less than 10.3 days. It has a metallic content lower than that of the Sun; various studies estimate its index metallicity between -0.25 and -0.44. It has an approximate mass between 45% and 49% of the solar mass and is a star with characteristics comparable to that of Lacaille 9352.

Planetary system Gliese 686 has one known super-Earth planet detected by radial velocity. It is orbiting close to the host star with a separation of 0.091 AU (13.6 Gm) and an orbital period of 15.5 days. Since the inclination of its orbit is unknown, only a lower bound on its mass can be determined: it has at least 6.6 times the mass of the planet Earth.

References

Worked examples

Example 1 — a first encounter with Gliese 686

Start with the simplest possible case. Write down what Gliese 686 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 Gliese 686 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 Gliese 686 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 Gliese 686

In research: Gliese 686 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 Gliese 686 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: Gliese 686 is common in secondary-school and first-year university syllabi. It links to neighbouring topics Durchmusterung objects, Gliese and GJ objects, Hercules (constellation), so understanding it makes those chapters shorter.
In everyday life: Look for Gliese 686 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 Gliese 686 in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what Gliese 686 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 Gliese 686 out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is Gliese 686 in simple terms?

Why does Gliese 686 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 Gliese 686?

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 Gliese 686.