astronomy

Kepler-442

Kepler-442 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 Kepler-442 rather than just read about it. In short: Kepler-442 is a K-type main-sequence star approximately 1,196 light years from Earth in the constellation Lyra. It is located within the field of vision of the Kepler spacecraft, the satellite that NASA's Kepler Mission used to detect planets that may be transiting their stars.

Key takeaways

Kepler-442 belongs to astronomy; place it in that map before memorising details.
Learn the definition first, then one example that makes the definition concrete.
Connect Kepler-442 to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of Kepler-442 from memory before moving on to harder problems.

Reference excerpt

Kepler-442 is a K-type main-sequence star approximately 1,196 light years from Earth in the constellation Lyra. It is located within the field of vision of the Kepler spacecraft, the satellite that NASA's Kepler Mission used to detect planets that may be transiting their stars. On January 6, 2015, along with the stars of Kepler-438 and Kepler-440, it was announced that the star has an extrasolar planet (a super-Earth) orbiting within the habitable zone, named Kepler-442b.

Nomenclature and history

Prior to Kepler observation, Kepler-442 had the 2MASS catalogue number 2MASS J19012797+3916482. In the Kepler Input Catalog it has the designation of KIC 4138008, and when it was found to have transiting planet candidates it was given the Kepler object of interest number of KOI-4742. Planetary candidates were detected around the star by NASA's Kepler Mission, a mission tasked with discovering planets in transit around their stars. The transit method that Kepler uses involves detecting dips in brightness in stars. These dips in brightness can be interpreted as planets whose orbits pass in front of their stars from the perspective of Earth, although other phenomenon can also be responsible which is why the term planetary candidate is used. Following the acceptance of the discovery paper, the Kepler team provided an additional moniker for the system of "Kepler-442". The discoverers referred to the star as Kepler-442, which is the normal procedure for naming the exoplanets discovered by the spacecraft. Hence, this is the name used by the public to refer to the star and its planet. Candidate planets that are associated with stars studied by the Kepler Mission are assigned the designations ".01" etc. after the star's name, in the order of discovery. If planet candidates are detected simultaneously, then the ordering follows the order of orbital periods from shortest to longest. Following these rules, there was only candidate planet were detected, with an orbital period of 112.3053 days. The designation b derive from the order of discovery. The designation of b is given to the first planet orbiting a given star, followed by the other lowercase letters of the alphabet. In the case of Kepler-442, there was only one planet detected, so only the letter b is used. The name Kepler-442 derives directly from the fact that the star is the catalogued 442nd star discovered by Kepler to have confirmed planets.

Stellar characteristics Kepler-442 is a K-type main sequence star that is approximately 61% the mass of and 60% the radius of the Sun. It has a temperature of 4402 K and is about 2.9 billion years old, but the margin of error here is quite large. In comparison, the Sun is about 4.6 billion years old and has a temperature of 5778 K. The star is somewhat poor in metals, with a metallicity ([Fe/H]) of about –0.37, or about 43% of the amount of iron and other heavier metals found in the Sun. The star's luminosity is a bit low for a star like Kepler-442, with a luminosity of around 12% of that of the solar luminosity. Kepler-442 orbits a star with an apparent magnitude of 14.976, rendering it too faint to be visible to the naked eye from Earth. This dimness, as well as its distance from Earth, poses a challenge for direct observation.

Planetary system

The only known planet transits the star; this means that the planet's orbit appear to cross in front of their star as viewed from the Earth's perspective. Its inclination relative to Earth's line of sight, or how far above or below the plane of sight it is, vary by less than one degree. This allows direct measurements of the planet's periods and relative diameters (compared to the host star) by monitoring the planet's transit of the star. Kepler-442b is a super-Earth with a radius 1.34 times that of Earth, and orbits well within the habitable zone. It is likely a rocky planet due to its radius. According to NASA, it was described as being one of the most Earth-like planets, in terms of size and temperature, yet found. It is just outside of the zone (around 0.362 AU) where tidal forces from its host star would be enough to tidally lock it.

See also Kepler Mission List of planetary systems

Notes

References

Worked examples

Example 1 — a first encounter with Kepler-442

Start with the simplest possible case. Write down what Kepler-442 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 Kepler-442 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 Kepler-442 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 Kepler-442

In research: Kepler-442 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 Kepler-442 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: Kepler-442 is common in secondary-school and first-year university syllabi. It links to neighbouring topics K-type main-sequence stars, Kepler-442, Kepler objects of interest, so understanding it makes those chapters shorter.
In everyday life: Look for Kepler-442 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 Kepler-442 in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what Kepler-442 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 Kepler-442 out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is Kepler-442 in simple terms?

Why does Kepler-442 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 Kepler-442?

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 Kepler-442.