astronomy

HD 136138

HD 136138 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 136138 rather than just read about it. In short: HD 136138, or HR 5692, is a binary star system in the Serpens Caput segment of the Serpens constellation. It has a golden hue like the Sun and is dimly visible to the naked eye with an apparent visual magnitude of 5.68; the light contribution from the companion is effectively negligible.

Key takeaways

HD 136138 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 136138 to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of HD 136138 from memory before moving on to harder problems.

Reference excerpt

HD 136138, or HR 5692, is a binary star system in the Serpens Caput segment of the Serpens constellation. It has a golden hue like the Sun and is dimly visible to the naked eye with an apparent visual magnitude of 5.68; the light contribution from the companion is effectively negligible. This system is located at a distance of approximately 420 light years from the Sun based on parallax. It is drifting closer with a radial velocity of −7.7 km/s and has a proper motion of 23.5 mas·yr−1. The radial velocity variation of this star was reported by J. R. de Medeiros and M. Mayor in 1999, and it was confirmed as a binary by A. Frankowski and colleagues in 2007 using proper motion measurements. It is an unresolved, single-lined spectroscopic binary system with an orbital period of 1.39 years and an eccentricity (ovalness) of 0.335. Proper motion measurements allow an estimate of the orbital inclination angle as ~43°. Their semimajor axis is around 2.0 AU, or double the distance from the Earth to the Sun. The stellar classification of the primary component is G8IIIa, indicating this is a evolved G-type giant star that has exhausted the supply of hydrogen at its core. It is a red clump giant that is generating energy through core helium fusion. There is some ambiguous evidence for this being a mild barium star of class Ba0.3, with the spectra showing marginal overabundances of s-process elements. A low level of X-ray emission has been detected, which appears to be coming from the star's corona. The high level of ultraviolet flux coming from this system strongly suggests the companion is a compact white dwarf. Mass estimates put it in the range of 0.6 to 0.8 times the mass of the Sun, and the temperature is around 30,400 K. It is possible that the earlier evolution of this component contaminated its partner with s-process elements, although the resulting interaction should have circularized the orbit to some degree. The dwarf has a visual magnitude of 15.3 and a hydrogen-dominated atmospheric class of DA1.7.

References

Worked examples

Example 1 — a first encounter with HD 136138

Start with the simplest possible case. Write down what HD 136138 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 136138 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 136138 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 136138

In research: HD 136138 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 136138 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 136138 is common in secondary-school and first-year university syllabi. It links to neighbouring topics Barium stars, Bright Star Catalogue objects, Durchmusterung objects, so understanding it makes those chapters shorter.
In everyday life: Look for HD 136138 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 136138 in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what HD 136138 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 136138 out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is HD 136138 in simple terms?

Why does HD 136138 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 136138?

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 136138.