A Closely-Packed System of Low-Mass, Low-Density Planets Transiting Kepler-11

TL;DR

This paper reports the discovery of six transiting planets around a single star by Kepler, including the smallest measured planets with substantial gas envelopes, providing insights into planetary system formation and dynamics.

Contribution

It presents the first detailed characterization of a multi-planet system with six transiting planets, revealing their sizes, masses, and orbital configurations.

Findings

Six transiting planets around a single star were observed.

The five inner planets are among the smallest with measured masses and sizes.

The planetary orbits suggest a history of energy dissipation during formation.

Abstract

When an extrasolar planet passes in front of its star (transits), its radius can be measured from the decrease in starlight and its orbital period from the time between transits. Multiple planets transiting the same star reveal more: period ratios determine stability and dynamics, mutual gravitational interactions reflect planet masses and orbital shapes, and the fraction of transiting planets observed as multiples has implications for the planarity of planetary systems. But few stars have more than one known transiting planet, and none has more than three. Here we report Kepler spacecraft observations of a single Sun-like star that reveal six transiting planets, five with orbital periods between 10 and 47 days plus a sixth one with a longer period. The five inner planets are among the smallest whose masses and sizes have both been measured, and these measurements imply substantial envelopes of light gases. The degree of coplanarity and proximity of the planetary orbits imply energy dissipation near the end of planet formation.