astronomy

HD 131664

HD 131664 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 131664 rather than just read about it. In short: HD 131664 is an 8th magnitude star in the southern constellation of Apus with an orbiting brown dwarf or stellar companion. Parallax measurements by the Gaia space observatory provide an estimated distance of 172.5 light years from the Earth.

Key takeaways

HD 131664 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 131664 to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of HD 131664 from memory before moving on to harder problems.

Reference excerpt

HD 131664 is an 8th magnitude star in the southern constellation of Apus with an orbiting brown dwarf or stellar companion. Parallax measurements by the Gaia space observatory provide an estimated distance of 172.5 light years from the Earth. The system is moving further away with a baseline heliocentric radial velocity of +35 km/s. The primary component is an ordinary G-type main-sequence star with a stellar classification of G3 V. The star is particularly metal-rich ([Fe/H] = 0.28) in comparison with the mean metallicity of the solar neighborhood. It is about 2.3 billion years old with a projected rotational velocity of 3 km/s. The star has 110% of the mass of the Sun and 116% times the Sun's radius. It is radiating 160% of the Sun's luminosity from its photosphere at an effective temperature of 5,901 K. The discovery of a brown dwarf in orbit around HD 131664 was announced on October 26, 2008 and designated HD 131664 b. The object was detected from Doppler measurements of the host star between 2004 and 2008. This object has a minimum mass of 18.15 times that of Jupiter and orbits in a long-period, eccentric orbit that completely overlaps the star's habitable zone. As of 2009, this period (1,951 days or 5.34 years) was among the dozen longest exoplanet periods known. Follow-up studies with data from the Hipparcos and Gaia satellites further constrained the predicted mass of the companion, providing a best estimate of 127.8±17.9 MJ, or about 0.12 times the mass of the Sun.

References

Worked examples

Example 1 — a first encounter with HD 131664

Start with the simplest possible case. Write down what HD 131664 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 131664 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 131664 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 131664

In research: HD 131664 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 131664 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 131664 is common in secondary-school and first-year university syllabi. It links to neighbouring topics Apus, Brown dwarfs, Durchmusterung objects, so understanding it makes those chapters shorter.
In everyday life: Look for HD 131664 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 131664 in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what HD 131664 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 131664 out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is HD 131664 in simple terms?

Why does HD 131664 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 131664?

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 131664.