astronomy

HD 138289

HD 138289 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 138289 rather than just read about it. In short: HD 138289, also known as HR 5757, is a probable spectroscopic binary located in the constellation Apus, the bird-of-paradise. It has an apparent magnitude of 6.18, placing it near the limit for naked eye.

Key takeaways

HD 138289 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 138289 to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of HD 138289 from memory before moving on to harder problems.

Reference excerpt

HD 138289, also known as HR 5757, is a probable spectroscopic binary located in the constellation Apus, the bird-of-paradise. It has an apparent magnitude of 6.18, placing it near the limit for naked eye. Gaia DR3 parallax measurements place the object 359 light years away and it is currently receding with a heliocentric radial velocity of 13.1 km/s. At its current distance, HD 138289's brightness is diminished by 0.25 magnitudes due to extinction from interstellar dust. It has an absolute magnitude of +1.21. The visible component has a stellar classification of K2.5 IIIb CN1.5 Ba+0.5, indicating that it is a red giant with an anomalous overabundance of cyano radicals in its spectrum. The IIIb luminosity class indicates that it is a lower luminosity giant star. The Ba+0.5 suffix states that it is a mild barium star, whose barium abundance might have come from a hidden white dwarf companion. HD 138289 is estimated to be 2.8 billion years old, enough time for it to cool and expand to 13 times the radius of the Sun. It is now on the horizontal branch, fusing helium at its core. At present it has 1.59 times the mass of the Sun and radiates 52.5 times the luminosity of the Sun from its enlarged photosphere at an effective temperature of 4,672 K. HD 138289 has a near solar metallicity and spins modestly with a poorly constrained projected rotational velocity of 5.2 km/s.

References

Illustrations

Worked examples

Example 1 — a first encounter with HD 138289

Start with the simplest possible case. Write down what HD 138289 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 138289 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 138289 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 138289

In research: HD 138289 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 138289 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 138289 is common in secondary-school and first-year university syllabi. It links to neighbouring topics Apus, Bright Star Catalogue objects, Durchmusterung objects, so understanding it makes those chapters shorter.
In everyday life: Look for HD 138289 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.

Ask Teacher Smith questions about this articleOpens your AI tutor with a question about “HD 138289” →

Affiliate

Preply — study more efficiently by working with a personal tutor. 50% off.

How to study HD 138289 in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what HD 138289 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 138289 out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is HD 138289 in simple terms?

Why does HD 138289 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 138289?

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 138289.