astronomy

Kepler-11

Kepler-11 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-11 rather than just read about it. In short: Kepler-11, also designated as 2MASS J19482762+4154328, is a Sun-like star slightly larger than the Sun in the constellation Cygnus, located some 2,110 light years from Earth. It is located within the field of vision of the Kepler space telescope, the satellite that NASA's Kepler Mission uses to detect planets that may be transiting their stars.

Key takeaways

Kepler-11 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-11 to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of Kepler-11 from memory before moving on to harder problems.

Reference excerpt

Kepler-11, also designated as 2MASS J19482762+4154328, is a Sun-like star slightly larger than the Sun in the constellation Cygnus, located some 2,110 light years from Earth. It is located within the field of vision of the Kepler space telescope, the satellite that NASA's Kepler Mission uses to detect planets that may be transiting their stars. Announced on 2 February 2011, the planetary system is among the most compact and flattest systems yet discovered. It is the first discovered case of a star system with six transiting planets. All discovered planets are larger than Earth, with the larger one being about Neptune's size.

Nomenclature and history Kepler-11 and its planets were discovered 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 move in front of their stars from the perspective of Earth. Kepler-11 is the first discovered exoplanetary system with more than three transiting planets. Kepler-11 is named for the Kepler Mission: It is the star with confirmed planets discovered in the Kepler field of view. The planets are named alphabetically: b, c, d, e, f, and g, distinguishers that are tagged onto the name of their home star.

Characteristics Kepler-11 is a G-type main-sequence star that is approximately 104% the mass of and 102% the radius of the Sun. It has a surface temperature of about 5836 K and is estimated to have an age of around 3.2 billion years. In comparison, the Sun is about 4.6 billion years old and has a surface temperature of 5778 K. With an apparent magnitude of 14.2, it is too faint to be seen with the naked eye.

Planetary system All known planets transit the star; this means that all six planets' orbits appear to cross in front of their star as viewed from the Earth's perspective. Their inclinations relative to Earth's line of sight, or how far above or below the plane of sight they are, vary by a little more than a degree. This allows direct measurements of the planets' periods and relative diameters (compared to the host star) by monitoring each planet's transit of the star. Simulations suggest that the mean mutual inclinations of the planetary orbits are about 1°, meaning the system is probably more coplanar (flatter) than the Solar System, where the corresponding figure is 2.3°. The estimated masses of planets b - f fall in the range between those of Earth and Neptune. Their estimated densities, all lower than that of Earth, imply that none of them have an Earth-like composition; a significant hydrogen/helium atmosphere is predicted for planets c, d, e, f, and g, while planet b may be surrounded by a steam atmosphere or perhaps by a hydrogen atmosphere. The low densities likely result from high-volume extended atmospheres that surround cores of iron, rock, and possibly H2O. The inner constituents of the Kepler-11 system were, at the time of their discoveries, the most comprehensively understood extrasolar planets smaller than Neptune. Currently, observations do not place a firm constraint on the mass of planet g (<25 ME). However, formation and evolution studies indicate that the mass of planet g is not much greater than about 7 ME. Kepler-11 planets may have formed in situ (i.e., at their observed orbital locations) or ex situ, that is, they may have started their formation farther away from the star while migrating inward through gravitational interactions with a gaseous protoplanetary disk. This second scenario predicts that a substantial fraction of the planets' mass is in H2O. Regardless of the formation scenario, the gaseous component of the planets accounts for less than about 20% of their masses but for ≈40 to ≈60% of their radii. In 2014, the dynamical simulation shown what the Kepler-11 planetary system have likely to undergone a substantial inward migration in the past, producing an observed pattern of lower-mass planets on tightest orbits. Additional yet unobserved gas giant planets on wider orbit are likely necessary for migration of smaller planets to proceed that far inward. The system is among the most compact known; the orbits of planets b - f would easily fit inside the orbit of Mercury, with g only slightly outside it. Despite this close packing of the orbits, dynamical integrations indicate the Kepler-11 system has the potential to be stable on a time scale of billions of years. However, it may be approaching instability due to a secular resonance involving b and c. If this happens, b will most likely become eccentric enough that it collides with c. None of the planets are in low-ratio orbital resonances, in which multiple planets gravitationally tug on and stabilize each other's orbits, resulting in simple ratios of their orbital periods. However, b and c are close to a 5:4 ratio. There could conceivably be other planets in the system that do not transit the star, but they would only be detectable by the effects of their gravity on the motion of the visible planets (much as how Neptune was discovered). The presence of additional gas giant planets is currently excluded up to orbital distance of 30 AU.

Illustrations

Worked examples

Example 1 — a first encounter with Kepler-11

Start with the simplest possible case. Write down what Kepler-11 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-11 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-11 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-11

In research: Kepler-11 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-11 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-11 is common in secondary-school and first-year university syllabi. It links to neighbouring topics Cygnus (constellation), G-type main-sequence stars, Kepler-11, so understanding it makes those chapters shorter.
In everyday life: Look for Kepler-11 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-11 in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what Kepler-11 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-11 out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is Kepler-11 in simple terms?

Why does Kepler-11 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-11?

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-11.