astronomy

K2-138b

K2-138b 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 K2-138b rather than just read about it. In short: K2-138b is a potentially rocky super-Earth exoplanet orbiting around the star K2-138. The planet, along with the four others in the system, was found by citizen scientists of the Exoplanet Explorers project on Zooniverse.

Key takeaways

K2-138b belongs to astronomy; place it in that map before memorising details.
Learn the definition first, then one example that makes the definition concrete.
Connect K2-138b to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of K2-138b from memory before moving on to harder problems.

Reference excerpt

K2-138b is a potentially rocky super-Earth exoplanet orbiting around the star K2-138. The planet, along with the four others in the system, was found by citizen scientists of the Exoplanet Explorers project on Zooniverse. It was the final planet found in the system and was officially announced in 2018. K2-138b is a planet with a radius of 1.57 R🜨, meaning it could be rocky. It orbits its host star every 2.35 days at a distance of 0.0338 AU. At this proximity, the planet is likely very hot and receives 486 times the stellar flux as Earth. The planet has a Mass of 3.1+1.1−1.1 M🜨 and a bulk density of 4.9+2.0−1.8 g/cm−3, which is an Earth-like density. The planet has likely a rocky core and a substantial atmospheric layer, composed of volatiles. The K2-138 system is unique for being the first exoplanet system discovered entirely by citizen scientists. The K2-138 system, including K2-138b will be studied with CHEOPS to further constrain the mass of the planets with transit-timing variation (TTV).

References

Worked examples

Example 1 — a first encounter with K2-138b

Start with the simplest possible case. Write down what K2-138b 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 K2-138b 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 K2-138b 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 K2-138b

In research: K2-138b 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 K2-138b 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: K2-138b is common in secondary-school and first-year university syllabi. It links to neighbouring topics Aquarius (constellation), Exoplanets discovered by K2, Exoplanets discovered in 2018, so understanding it makes those chapters shorter.
In everyday life: Look for K2-138b 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 K2-138b in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what K2-138b 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 K2-138b out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is K2-138b in simple terms?

Why does K2-138b 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 K2-138b?

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 K2-138b.