astronomy

K2-3d

K2-3d 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 K2-3d rather than just read about it. In short: K2-3d, also known as EPIC 201367065 d, is a confirmed exoplanet of probable mini-Neptune type orbiting the red dwarf star K2-3, and the outermost of three such planets discovered in the system. It is located 143 light-years (44 parsecs) away from Earth in the constellation of Leo.

Key takeaways

K2-3d belongs to astronomy; place it in that map before memorising details.
Learn the definition first, then one example that makes the definition concrete.
Connect K2-3d to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of K2-3d from memory before moving on to harder problems.

Reference excerpt

K2-3d, also known as EPIC 201367065 d, is a confirmed exoplanet of probable mini-Neptune type orbiting the red dwarf star K2-3, and the outermost of three such planets discovered in the system. It is located 143 light-years (44 parsecs) away from Earth in the constellation of Leo. 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. It was the first planet in the Kepler "Second Light" mission to receive the letter "d" designation for a planet. Its discovery was announced in January 2015.

Characteristics

Mass, radius, density and temperature K2-3d is a super-Earth or a mini-Neptune, meaning it has a mass and radius bigger than Earth's, but smaller than that of the ice giants Uranus and Neptune. It has an equilibrium temperature of 305 K (32 °C; 89 °F) and a radius of 1.5 to 1.6 R🜨. The planet is likely to be a mini-Neptune, with no solid surface. While originally estimated to have a very high density, later analysis of HARPS data in 2018 constrained the mass to less than 4 M🜨 to a 1σ confidence, and by 2023 this upper limit has been reduced to 2 M🜨. This corresponds to a relatively low density, similar to that of Neptune, suggesting a very large volatile layer and significantly reducing the potential habitability of the world.

Host Star

The planet orbits a (M-type) red dwarf star named K2-3, orbited by a total of three known planets, of which K2-3d has the longest orbital period. The star has a mass of 0.60 M☉ and a radius of 0.56 R☉. It has a temperature of 3896 K and is about 1 billion years old. 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 12.168. Therefore, it is too dim to be seen with the naked eye.

Orbital statistics K2-3d orbits its host star, which has about 6% of the Sun's luminosity, with an orbital period of 44 days and an orbital radius of about 0.2 times that of Earth (compared to the distance of Mercury from the Sun, which is about 0.38 AU).

Habitability The planet orbits on the edge of the inner (empirical) habitable zone, a region where, with the proper atmospheric properties and pressure, liquid water may exist on the surface of the planet. However, it is very likely tidally locked to its star, with one side facing towards its star in scorching heat, and the opposite side in bitter darkness. Despite this, there is an area – the terminator line – where the surface temperatures may be comfortable enough to support liquid water. However, given that most models of the habitable zone parameters put K2-3d slightly beyond the inner edge of the habitable zone, it is likely to be too hot even at the terminator line and thus not habitable at all. Also, the stellar flux for the planet is an abnormally high 1.4 times that of Earth, which could result in surface temperatures of up to 400–500 K (127–227 °C; 260–440 °F) because of a runaway greenhouse effect.

Discovery The planet, along with the other two known planets in the K2-3 system, was announced in early January 2015 as part of the first results from the second mission of the Kepler spacecraft. With this, it was the first multiplanetary system of the mission as well.

See also List of potentially habitable exoplanets

References

Illustrations

Worked examples

Example 1 — a first encounter with K2-3d

Start with the simplest possible case. Write down what K2-3d 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 K2-3d 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 K2-3d 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 K2-3d

In research: K2-3d 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 K2-3d 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: K2-3d is common in secondary-school and first-year university syllabi. It links to neighbouring topics Exoplanets discovered by K2, Exoplanets discovered in 2015, K2-3, so understanding it makes those chapters shorter.
In everyday life: Look for K2-3d 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.

Affiliate

Preply — study more efficiently by working with a personal tutor. 50% off.

How to study K2-3d in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what K2-3d 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 K2-3d out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is K2-3d in simple terms?

Why does K2-3d 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 K2-3d?

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 K2-3d.