Kepler-90b

Lore & Background

Kepler-90b was discovered by NASA's Kepler Mission using the transit method, which detects dips in brightness when a planet crosses in front of its star. As the first planet found in the system, it received the designation Kepler-90b, with subsequent planets given lowercase letters in order of discovery. The star itself was catalogued as the 90th star discovered by Kepler to have confirmed planets.

The Kepler-90 system is the only eight-planet system from Kepler and the second known after the Solar System. The five innermost exoplanets, including Kepler-90b, are likely tidally locked, meaning one side permanently faces the star in eternal daylight and the other side in eternal darkness. The six inner planets range from super-Earths to mini-Neptunes in size, with rocky planets nearer the star and gas giants farther away.

Reader's Guide

Kepler-90b is significant as the first discovered member of the only Kepler system with eight confirmed planets, matching the Solar System in planet count. Its discovery helped validate the Kepler mission's 'validation by multiplicity' confirmation method, as the six inner planets met all requirements for confirmation. The system's architecture, with inner rocky planets and outer gas giants, shows similarities to the Solar System. Kepler-90b's orbital period is part of a near-resonance chain: the period ratios b:c, c:i, and i:d are close to 4:5, 3:5, and 1:4, respectively. The presence of outer gas giants like Kepler-90g and h is thought to facilitate the formation of such closely packed resonances among inner super-Earths. The system's stability has been confirmed by Hill stability tests and orbital integration.

Did You Know?

• Kepler-90b is one of five innermost exoplanets in the system that are likely tidally locked.
• Kepler-90b's orbital period is part of a near 4:5 resonance with Kepler-90c.
• The star Kepler-90 is an F-type star about 120% the mass and radius of the Sun.