astronomy

K2-239

K2-239 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 K2-239 rather than just read about it. In short: K2-239 (also designated EPIC 248545986) is a small red dwarf star in the constellation Sextans, about 32 parsecs (101 light-years) away from Earth. Observed by the Kepler Space Telescope during Campaign 14 of its K2 "Second Light" mission, it was found to have three hot, likely rocky Earth-sized planets in orbit around it.

Key takeaways

K2-239 belongs to astronomy; place it in that map before memorising details.
Learn the definition first, then one example that makes the definition concrete.
Connect K2-239 to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of K2-239 from memory before moving on to harder problems.

Reference excerpt

K2-239 (also designated EPIC 248545986) is a small red dwarf star in the constellation Sextans, about 32 parsecs (101 light-years) away from Earth. Observed by the Kepler Space Telescope during Campaign 14 of its K2 "Second Light" mission, it was found to have three hot, likely rocky Earth-sized planets in orbit around it.

Stellar characteristics K2-239 is a small red dwarf star of spectral class M3V. It is 40% the mass and 36% the radius of the Sun with just 0.016 times the luminosity. It has a temperature of 3420 K and its age is unknown. For comparison, the Sun has a temperature of 5778 K and is 4.5 billion years old. K2-239 has a visual magnitude of 14.549, far too dim to see with the unaided eye. It is also one of the closer systems found by Kepler, only about 101 light-years away from Earth.

Planetary System

K2-239 has a system of three small, Earth-sized planets in a tight 2:3:4 orbital resonance chain. All of them are between 1.0 and 1.1 times the size of Earth, meaning they are very likely to be rocky. The discovery team estimated their masses to range from 0.9 M🜨 to 1.4 M🜨, consistent with a rocky composition for each of the planets. Due to their proximity to K2-239 they are all hot; however, because the host star is just 1.6% as luminous as the Sun, they are much cooler than if they were placed around the Sun. For albedoes of 0 they would have equilibrium temperatures of 502 K (229 °C; 444 °F) for K2-239b, 427 K (154 °C; 309 °F) for K2-239c, and 399 K (126 °C; 259 °F) for K2-239d. None of them are cool enough to host liquid water or be considered potentially habitable.

Worked examples

Example 1 — a first encounter with K2-239

Start with the simplest possible case. Write down what K2-239 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 K2-239 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 K2-239 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 K2-239

In research: K2-239 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 K2-239 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: K2-239 is common in secondary-school and first-year university syllabi. It links to neighbouring topics Exoplanets discovered by K2, M-type main-sequence stars, Sextans, so understanding it makes those chapters shorter.
In everyday life: Look for K2-239 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 K2-239 in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what K2-239 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 K2-239 out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is K2-239 in simple terms?

Why does K2-239 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 K2-239?

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 K2-239.