astronomy

K2-72e

K2-72e 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 K2-72e rather than just read about it. In short: K2-72e (also known by its EPIC designation EPIC 206209135.04), is a confirmed exoplanet, likely rocky, orbiting within the habitable zone of the red dwarf star K2-72, the outermost of four such planets discovered in the system by NASA's Kepler spacecraft on its "Second Light" mission. It is located about 217.1 light-years (66.56 parsecs, or nearly 2.0538×1015 km) away from Earth in the constellation of Aquarius.

Key takeaways

K2-72e belongs to astronomy; place it in that map before memorising details.
Learn the definition first, then one example that makes the definition concrete.
Connect K2-72e to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of K2-72e from memory before moving on to harder problems.

Reference excerpt

K2-72e (also known by its EPIC designation EPIC 206209135.04), is a confirmed exoplanet, likely rocky, orbiting within the habitable zone of the red dwarf star K2-72, the outermost of four such planets discovered in the system by NASA's Kepler spacecraft on its "Second Light" mission. It is located about 217.1 light-years (66.56 parsecs, or nearly 2.0538×1015 km) away from Earth in the constellation of Aquarius. The exoplanet was found by using the transit method, in which the dimming effect that a planet causes as it crosses in front of its star is measured.

Characteristics

Mass, radius, and temperature K2-72e is an Earth-sized exoplanet, meaning it has a mass and radius close to that of Earth. It has an equilibrium temperature of 261 K (−12 °C; 10 °F). It has a radius of 1.29 R🜨., and a mass of 2.2 M🜨, depending on its composition.

Host star

The planet orbits a (M-type) red dwarf star named K2-72, orbited by a total of four planets, of which K2-72e has the longest orbital period. The star has a mass of 0.27 M☉ and a radius of 0.33 R☉. It has a temperature of 3360 K and its age is unknown. In comparison, the Sun is 4.6 billion years old and has a surface temperature of 5778 K. The star's apparent magnitude, or how bright it appears from Earth's perspective, is 15.309. Therefore, it is too dim to be seen with the naked eye and can only be observed with a telescope.

Orbit K2-72e orbits its host star with an orbital period of 24 days and an orbital radius of about 0.1 times that of Earth's (compared to the distance of Mercury from the Sun, which is about 0.38 AU).

Habitability

The exoplanet, along with K2-72c, were announced to be orbiting in the habitable zone of its parent star, the region where, with the correct conditions and atmospheric properties, liquid water may exist on the surface of the planet. K2-72e has a radius of 1.29 R🜨, so it is likely rocky. Its host star is a red dwarf, with about a fifth as much mass than the Sun does. As a result, stars like K2-72 have the ability to live up to 1–2 trillion years, hundreds of times longer than the Sun will live. The planet is very likely tidally locked, with one side of its hemisphere permanently facing towards the star, while the opposite side shrouded in eternal darkness. It receives 11% more insolation than Earth does, so any oceans present are potentially vulnerable to boiling away, therefore possibly reducing the chance of habitability.

Discovery The planet, along with the other three planets in the K2-72 system, were announced in mid-July 2016 as part of the new results from the second mission of the Kepler spacecraft.

See also List of potentially habitable exoplanets

References

Illustrations

Worked examples

Example 1 — a first encounter with K2-72e

Start with the simplest possible case. Write down what K2-72e 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 K2-72e 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 K2-72e 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 K2-72e

In research: K2-72e 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 K2-72e 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: K2-72e is common in secondary-school and first-year university syllabi. It links to neighbouring topics Aquarius (constellation), Exoplanets discovered by K2, Exoplanets discovered in 2016, so understanding it makes those chapters shorter.
In everyday life: Look for K2-72e 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 K2-72e in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what K2-72e 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 K2-72e out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is K2-72e in simple terms?

Why does K2-72e 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 K2-72e?

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 K2-72e.