astronomy

Gliese 86

Gliese 86 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 86 rather than just read about it. In short: Gliese 86 (13 G. Eridani, HD 13445) is a K-type main-sequence star 35 light-years away in the constellation of Eridanus.

Key takeaways

Gliese 86 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 86 to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of Gliese 86 from memory before moving on to harder problems.

Reference excerpt

Gliese 86 (13 G. Eridani, HD 13445) is a K-type main-sequence star 35 light-years away in the constellation of Eridanus. It has been confirmed that a white dwarf orbits the primary star. In 1998 the European Southern Observatory announced that an extrasolar planet was also orbiting the star.

Stellar components The primary companion (Gliese 86 A) is a K-type main-sequence star of spectral type K1V. The characteristics in comparison to the Sun are 83% the mass, 79% the radius, and 50% the luminosity. The star has a close-orbiting massive Jovian planet. Gliese 86 B is a white dwarf located around 21 AU from the primary star, making the Gliese 86 system one of the tightest binaries known to host an extrasolar planet. It was discovered in 2001 and initially suspected to be a brown dwarf, but high contrast observations in 2005 suggested that the object is probably a white dwarf, as its spectrum does not exhibit molecular absorption features which are typical of brown dwarfs. Assuming the white dwarf has a mass about half that of the Sun and that the linear trend observed in radial velocity measurements is due to Gliese 86 B, a plausible orbit for this star around Gliese 86 A has a semimajor axis of 18.42 AU and an eccentricity of 0.3974. When both stars were on the main sequence, the separation between the two stars was closer, at around 9 AU. More precise measurements for the white dwarf give it a mass of 55% the mass of the Sun and a temperature of around 8200 K. It is likely to have been an A5 star when on the main sequence.

Planetary system The planet Gliese 86 b was discovered by the Swiss 1.2 m Leonhard Euler Telescope operated by the Geneva Observatory. Such an object was formed from a protoplanetary disk that was truncated at 2 AU from the parent star. The radial velocity measurements of Gliese 86 show a linear trend once the motion due to this planet are taken out. This may be associated with the orbital motion of the white dwarf companion.

See also List of exoplanets discovered before 2000 - Gliese 86b

References

External links "Gliese 86 / HR 637 AB". SolStation. Archived from the original on 2007-08-09. Retrieved 2008-08-02.

Illustrations

Worked examples

Example 1 — a first encounter with Gliese 86

Start with the simplest possible case. Write down what Gliese 86 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 86 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 86 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 86

In research: Gliese 86 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 86 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 86 is common in secondary-school and first-year university syllabi. It links to neighbouring topics Astronomical objects discovered in 2001, Bright Star Catalogue objects, Durchmusterung objects, so understanding it makes those chapters shorter.
In everyday life: Look for Gliese 86 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 86 in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what Gliese 86 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 86 out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is Gliese 86 in simple terms?

Gliese 86 (13 G. Eridani, HD 13445) is a K-type main-sequence star 35 light-years away in the constellation of Eridanus.

Why does Gliese 86 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 86?

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 86.