astronomy

HD 137388

HD 137388 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 137388 rather than just read about it. In short: HD 137388 is an orange-hued star in the southern constellation of Apus. It has the proper name Karaka, after the native New Zealand karaka tree.

Key takeaways

HD 137388 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 137388 to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of HD 137388 from memory before moving on to harder problems.

Reference excerpt

HD 137388 is an orange-hued star in the southern constellation of Apus. It has the proper name Karaka, after the native New Zealand karaka tree. The name was assigned by representatives of New Zealand in the IAU's NameExoWorlds contest. The star is too faint to be visible to the naked eye, having an apparent visual magnitude of 8.70. It is located at a distance of 132 light years from the Sun based on parallax. The star is drifting further away with a radial velocity of +26 km/s, having come as close as 52.9 light-years some 1.2 million years ago. It has an absolute magnitude of 5.75. The stellar classification of HD 137388 is K2IV, matching that of an evolving subgiant star. However, in 2011 Dumusque and colleagues found a class of K0/K1V, suggesting it is instead a K-type main-sequence star. It is around three billion years old and is spinning with a projected rotational velocity of 2.2 km/s. The star shows a magnetic activity cycle, similar to the solar cycle. It has 93% of the mass of the Sun and 86% of the Sun's radius. Based on the abundance of iron in the spectrum, it is a high metallicity star with a greater abundance of heavy elements compared to the Sun. The star is radiating 53% of the luminosity of the Sun from its photosphere at an effective temperature of 5,297 K.

Planetary system Radial velocity studies indicate that it has a planet, originally named HD 137388 b (mass 0.223 MJ, period 330d). It orbits at a typical distance of 0.89 AU with an eccentricity of 0.36, completely overlapping the star's habitable zone. The planet was officially designated Kererū, the Māori name of the New Zealand pigeon, by the IAU in the same contest that named its parent star.

References

Worked examples

Example 1 — a first encounter with HD 137388

Start with the simplest possible case. Write down what HD 137388 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 137388 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 137388 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 137388

In research: HD 137388 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 137388 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 137388 is common in secondary-school and first-year university syllabi. It links to neighbouring topics Apus, Durchmusterung objects, Giant planets in the habitable zone, so understanding it makes those chapters shorter.
In everyday life: Look for HD 137388 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 137388 in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what HD 137388 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 137388 out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is HD 137388 in simple terms?

HD 137388 is an orange-hued star in the southern constellation of Apus. It has the proper name Karaka, after the native New Zealand karaka tree.

Why does HD 137388 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 137388?

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 137388.