astronomy

Kepler-9b

Kepler-9b 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-9b rather than just read about it. In short: Kepler-9b is one of the first planets discovered outside the Solar System (exoplanets) by NASA's Kepler Mission. It revolves around the star Kepler-9 within the constellation Lyra.

Key takeaways

Kepler-9b 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-9b to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of Kepler-9b from memory before moving on to harder problems.

Reference excerpt

Kepler-9b is one of the first planets discovered outside the Solar System (exoplanets) by NASA's Kepler Mission. It revolves around the star Kepler-9 within the constellation Lyra. Kepler-9b is the largest of three planets detected in the Kepler system by transit method; its mass is roughly half that of the planet Saturn, and it is the largest planet in its system. Kepler-9b and Kepler-9c display a phenomenon called orbital resonance, in which gravitational pull from each planet alters and stabilizes the orbit of the other. The planet's discovery was announced on August 26, 2010.

Nomenclature and history Kepler-9b's name denotes that it is the first exoplanet discovered in orbit around the star Kepler-9. The star, in turn, was named for the Kepler Mission, a NASA project designed to search for Earth-like planets. Kepler-9's planets were among 700 planetary candidates collected during Kepler's first 43 days online. The system in particular was flagged as one of five systems that appeared to have held over one transiting exoplanet. Kepler-9b's discovery was announced on August 26, 2010. It was the part of the first confirmed star system in which multiple planets transited the same star. The planet was confirmed by the Kepler satellite by the transit method, in which the planet passes across the face of its star in relation to Earth, dimming that star's light by a small amount; this light difference is then used to determine the planet and several of its characteristics, including size and distance from its home star. Initial estimates for Kepler-9b's mass were refined by the W. M. Keck Observatory at Mauna Kea, Hawaii. In doing so, scientists found that Kepler-9b is the larger of the two gas planets discovered in the Kepler-9 system, although in mass it is smaller than planet Saturn.

Characteristics Kepler-9b is a gas planet that has a mass approximately 43 times that of the Earth; thus, it is about one-half the mass of the planet Saturn. It has a radius of approximately 0.842 RJ, or about 80% the radius of Jupiter. The planet orbits Kepler-9 every 19.243 days, and it lies some 0.14 AU from the star. To compare, planet Mercury's average distance from the Sun is .387 AU and takes 87.969 days to complete an orbit. Kepler-9b is the second-closest planet to its star in the Kepler-9 system. The first known case of orbital resonance in transiting exoplanets has been noted between Kepler-9b and Kepler-9c. The two planets, whose orbits correspond in a roughly 1:2 ratio, maintain the orbit of the other by gravitational tug. Kepler-9b's orbit grows, on average, four minutes longer every orbital period. Eventually, this trend will reverse and increase. Over time, it can be seen that the planets' orbits oscillate slightly above and below the 1:2 ratio. Alycia Weinberger of the Carnegie Institution has stated that the Kepler-9 gas giants probably formed further away from the star than they are, and the appearance of the orbital resonance phenomenon may help explain the history of their inward migration.

Other planets in the Kepler-9 system Kepler-9c Kepler-9d

References

External links Media related to Kepler-9 b at Wikimedia Commons

Illustrations

Worked examples

Example 1 — a first encounter with Kepler-9b

Start with the simplest possible case. Write down what Kepler-9b 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-9b 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-9b 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-9b

In research: Kepler-9b 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-9b 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-9b is common in secondary-school and first-year university syllabi. It links to neighbouring topics Exoplanets discovered by the Kepler space telescope, Exoplanets discovered in 2010, Exoplanets with Kepler designations, so understanding it makes those chapters shorter.
In everyday life: Look for Kepler-9b 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-9b in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what Kepler-9b 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-9b out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is Kepler-9b in simple terms?

Kepler-9b is one of the first planets discovered outside the Solar System (exoplanets) by NASA's Kepler Mission. It revolves around the star Kepler-9 within the constellation Lyra.

Why does Kepler-9b 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-9b?

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-9b.