Kepler-42b

Lore & Background

Kepler-42b was discovered as part of a three-planet system using the Kepler Space Telescope, with the system's detection announced in February 2011 and confirmed on 10 January 2012. The planet's radius is smaller than Earth's, comparable to that of Mars or Venus, and it orbits extremely close to its host star. The star itself is one of the faintest in the Kepler field with confirmed planets, but the planets' small size was offset by the star's small radius, causing a larger fraction of starlight to be blocked during transits.

The orbital eccentricity of Kepler-42b remains unknown, as it has not been established by methods such as the radial velocity technique. The system's compact orbits and small planetary radii make it resemble the moon systems of giant planets like Jupiter or Saturn more than the Solar System. The equilibrium temperature of Kepler-42b can be estimated based on the star's luminosity and effective temperature, though specific values for this planet are not provided in the available notes.

Reader's Guide

Kepler-42b is significant as part of only the second known system containing planets of Earth's radius or smaller, following the Kepler-20 system. Its discovery demonstrated that the Kepler Space Telescope could detect very small planets around faint, low-luminosity stars by leveraging the star's small size to increase the transit depth. The system's architecture, with multiple sub-Earth-sized planets in very close orbits, provides a contrast to the Solar System and supports the idea that such compact configurations may be common around red dwarfs. The planet's small size and proximity to its star also highlight the challenges of characterizing such worlds, as orbital parameters like eccentricity remain unknown without additional observational methods. Kepler-42b contributes to the growing census of terrestrial-sized exoplanets and informs models of planetary formation and habitability around low-mass stars.

Did You Know?

• Kepler-42b orbits a red dwarf star with only 0.13 times the Sun's mass and 0.17 times its radius.
• The star Kepler-42 has a luminosity of just 0.24% of the Sun's.
• Kepler-42b is one of three known planets in the system, all smaller than Earth in radius.
• The system was confirmed on 10 January 2012 using data from the Kepler Space Telescope.