astronomy

Kepler-4

Kepler-4 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-4 rather than just read about it. In short: Kepler-4 is a sunlike star located about 1626 light-years away in the constellation Draco. It is in the field of view of the Kepler Mission, a NASA operation purposed with finding Earth-like planets.

Key takeaways

Kepler-4 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-4 to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of Kepler-4 from memory before moving on to harder problems.

Reference excerpt

Kepler-4 is a sunlike star located about 1626 light-years away in the constellation Draco. It is in the field of view of the Kepler Mission, a NASA operation purposed with finding Earth-like planets. Kepler-4b, a Neptune-sized planet that orbits extremely close to its star, was discovered in its orbit and made public by the Kepler team on January 4, 2010. Kepler-4b was the first discovery by the Kepler satellite, and its confirmation helped to demonstrate the spacecraft's effectiveness.

Nomenclature and history Kepler-4 is named for the Kepler spacecraft, a NASA telescope tasked with finding Earth-like planets that transit their stars as seen from Earth. As the previous three planets that Kepler confirmed had already been confirmed by others, Kepler-4 and its planet were the first to be discovered by the Kepler team. The star and its system were announced in Washington, D.C. at the 215th meeting of the American Astronomical Society on January 4, 2010, along with Kepler-5, Kepler-6, Kepler-7, and Kepler-8. Of the presented planets, Kepler-4b was the smallest, around the size of planet Neptune. The discovery of Kepler-4b and the other planets presented at the AAS meeting helped to confirm that the Kepler spacecraft was indeed functional. The Harlan J. Smith Telescope at McDonald Observatory in Fort Davis, Texas was used by astronomers from the University of Texas at Austin to follow up on Kepler's discoveries and confirm them. Telescopes in Hawaii, California, Arizona, and the Canary Islands were also used to confirm the findings.

Characteristics

Kepler-4 is a G0-type star, which is similar to the Sun, except slightly brighter. The star is 1.117 Msun and 1.555 Rsun, or 111% the mass of and 155% the radius of the Sun. With a metallicity of .09 (± 0.10) [Fe/H], Kepler-4 is more metal-rich than the Sun, a figure that is important in that metal-rich stars tend to have orbiting planets more often than metal-poor stars. Kepler-4 is also about 6.7 billion years old. In comparison, the Sun is 4.6 billion years old. In addition, Kepler-4 has an effective temperature of 5781 (± 76) K, which is almost identical, within the errors, to that of the Sun, which is 5778 K. As seen from Earth, Kepler-4 has an apparent magnitude of 12.7. It is, as a result, not visible with the naked eye.

Planetary system Kepler-4b's discovery was announced on January 4, 2010. It is the size of planet Neptune, at 0.077 MJ (7% the mass of Jupiter) and 0.357 RJ (36% the radius of Jupiter). The planet orbits its star every 3.213 days at 0.045 AU from the star. This distance compares to planet Mercury, which is 0.39 AU from the Sun. Kepler-4's eccentricity was assumed to be 0, however a subsequent independent reanalysis of the discovery data found a value of 0.25 ± 0.12. Likewise, the temperature of the planet is assumed to be 1650 K, far hotter than Jupiter's, which is assumed to be 124 K (not considering its internal heat and atmosphere). A search for transit-timing variations in all 17 quarters of Kepler data did not detect any evidence of additional planets.

See also List of extrasolar planets Kepler Mission

References

Worked examples

Example 1 — a first encounter with Kepler-4

Start with the simplest possible case. Write down what Kepler-4 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-4 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-4 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-4

In research: Kepler-4 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-4 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-4 is common in secondary-school and first-year university syllabi. It links to neighbouring topics Draco (constellation), G-type subgiants, Kepler objects of interest, so understanding it makes those chapters shorter.
In everyday life: Look for Kepler-4 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-4 in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what Kepler-4 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-4 out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is Kepler-4 in simple terms?

Kepler-4 is a sunlike star located about 1626 light-years away in the constellation Draco. It is in the field of view of the Kepler Mission, a NASA operation purposed with finding Earth-like planets.

Why does Kepler-4 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-4?

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-4.