astronomy

HD 139664

HD 139664 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 139664 rather than just read about it. In short: HD 139664 is a single star in the southern constellation of Lupus. It has the Bayer designation g Lupi; HD 139664 is the star's identifier from the Henry Draper Catalogue.

Key takeaways

HD 139664 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 139664 to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of HD 139664 from memory before moving on to harder problems.

Reference excerpt

HD 139664 is a single star in the southern constellation of Lupus. It has the Bayer designation g Lupi; HD 139664 is the star's identifier from the Henry Draper Catalogue. It has a yellow-white hue and is visible to the naked eye with an apparent visual magnitude of 4.64. The star is located at a distance of 57 light years from the Sun based on parallax, and it is drifting closer with a radial velocity of −7 km/s. It is a member of the Hercules-Lyra association of co-moving stars. This is an F-type main-sequence star with a stellar classification of F3/5V, which indicates it is generating energy through core hydrogen fusion. The estimated age is poorly constrained at around one billion years, but the age of the Hercules-Lyra association to which it belongs is 257±46 million years. It has a moderately high rate of spin, showing a projected rotational velocity of 71.6 km/s. The star has 1.37 times the mass of the Sun and 1.26 times the Sun's radius. It is radiating 3.31 times the luminosity of the Sun from its photosphere at an effective temperature of 6,704 K.

Debris disk

A debris disk has been imaged around this star using the coronagraphic mode of the ACS instrument on the Hubble Space Telescope. The disk appears to have a dust maximum at 83 AU from the star and a sharp outer boundary at 109 AU. These features may be caused by gravitational perturbations from planets orbiting the star.

References

Illustrations

Worked examples

Example 1 — a first encounter with HD 139664

Start with the simplest possible case. Write down what HD 139664 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 139664 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 139664 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 139664

In research: HD 139664 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 139664 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 139664 is common in secondary-school and first-year university syllabi. It links to neighbouring topics Bayer objects, Bright Star Catalogue objects, Circumstellar disks, so understanding it makes those chapters shorter.
In everyday life: Look for HD 139664 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 139664 in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what HD 139664 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 139664 out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is HD 139664 in simple terms?

HD 139664 is a single star in the southern constellation of Lupus. It has the Bayer designation g Lupi; HD 139664 is the star's identifier from the Henry Draper Catalogue.

Why does HD 139664 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 139664?

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 139664.