Kepler-11f

Lore & Background

Kepler-11f was announced to the public on February 2, 2011, after follow-up investigations at several observatories, with analysis published the next day in the journal Nature. It is the fifth planet from its star, orbiting at 0.25 AU every 46.68876 days. Its orbital eccentricity is unknown. The planet's mass is estimated at 2.3 times Earth's mass, though it may range from 1.1 to 4.5 Earth masses. Its radius is 2.61 times Earth's radius, giving it a density of about 0.7 g/cm³, comparable to Saturn. This low density, shared with planets d and e, suggests a hydrogen–helium atmosphere that accounts for 70–80% of the planet's volume but only a few percent of its mass. The inner planets b and c lack such thick atmospheres due to stellar irradiation. Kepler-11f formed within the first few million years of the system's existence, when a protoplanetary disk was still present.

Reader's Guide

Kepler-11f is part of the first system discovered with more than three transiting planets, making it a landmark in exoplanet science. Its low density, comparable to Saturn's, classifies it as a 'gas dwarf'—a small planet with a substantial hydrogen–helium envelope. This characteristic distinguishes it from the inner planets of the system, whose atmospheres were stripped by stellar radiation. The Kepler-11 system is the most compact and flattest planetary system yet discovered, with the five inner planets' orbits fitting within Mercury's orbit. Kepler-11f's discovery, along with its five siblings, demonstrated the Kepler telescope's ability to detect multiple transiting planets in a single system, providing insights into planetary formation and atmospheric retention. The system's age, estimated at eight billion years, and its star's similarity to the Sun offer a comparative laboratory for understanding planetary evolution over long timescales.

Did You Know?

• Kepler-11f is the least massive of the six planets in the Kepler-11 system.
• Its density is lower than water and comparable to Saturn's.
• The planet's hydrogen–helium atmosphere accounts for 70–80% of its volume.
• Kepler-11f orbits its star every 46.68876 days at a distance of 0.25 AU.