astronomy

Kepler-90g

Kepler-90g 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-90g rather than just read about it. In short: Kepler-90g (also known by its Kepler Object of Interest designation KOI-351.02) is a super-puff exoplanet orbiting the early G-type main sequence star Kepler-90, one of eight planets around this star discovered using NASA's Kepler space telescope. It is located about 2,840 light-years (870 pc) from Earth, in the constellation Draco.

Key takeaways

Kepler-90g 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-90g to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of Kepler-90g from memory before moving on to harder problems.

Reference excerpt

Kepler-90g (also known by its Kepler Object of Interest designation KOI-351.02) is a super-puff exoplanet orbiting the early G-type main sequence star Kepler-90, one of eight planets around this star discovered using NASA's Kepler space telescope. It is located about 2,840 light-years (870 pc) from Earth, in the constellation Draco. 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 orbits its parent star about every 210.5 days at a distance of 0.71 astronomical units. Kepler-90g's orbital period changes by 25.7 hours between two consecutive transits, caused by gravitational perturbations from other planets in the system. Additionally, changes in the depth and duration of transit events led to an exomoon being hypothesized to orbit this planet. However, this candidate moon was later found to be a false positive. A 2020 analysis of transit-timing variations of Kepler-90g and h found a best-fit mass of 15+0.9−0.8 M🜨 for planet g. This is between the masses of Uranus and Neptune. Given a transit-derived radius of 8.1 R🜨, Kepler-90g was found to have an extremely low density of 0.15±0.05 g/cm3, unusually inflated for its mass and insolation. Several possible explanations for its apparently low density include a puffy planet with a dusty atmosphere or a smaller planet surrounded by a tilted wide ring system (albeit the latter option is less likely due to the lack of evidence for rings in transit data).

Host star

The planet orbits a G-type star named Kepler-90, its host star. The star is 1.2 times as massive as the Sun and is 1.2 times as large as the Sun. It is estimated to be 2 billion years old, with a surface temperature of 6080 K. In comparison, the Sun is about 4.6 billion years old and has a surface temperature of 5778 K.

See also Kepler-1625b Kepler-51 HIP 41378 f

References

Illustrations

Worked examples

Example 1 — a first encounter with Kepler-90g

Start with the simplest possible case. Write down what Kepler-90g 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-90g 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-90g 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-90g

In research: Kepler-90g 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-90g 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-90g 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 2013, Giant planets, so understanding it makes those chapters shorter.
In everyday life: Look for Kepler-90g 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-90g in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what Kepler-90g 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-90g out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is Kepler-90g in simple terms?

Why does Kepler-90g 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-90g?

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-90g.