Kepler-93b

Lore & Background

Kepler-93b was discovered in February 2014 by astronomer Geoffrey Marcy and his team, transiting the Sun-like star Kepler-93. Its radius was measured with exceptional precision in July 2014, with an uncertainty of just 0.019 R🜨, the most accurate exoplanet radius measurement then achieved. The planet is substantially denser than Earth, with a mass of roughly 4 M🜨 initially, later revised upward to 4.66 M🜨 in 2023, yielding a density of 7.93 g/cm³—similar to that of metallic iron. Its interior is likely similar to Earth and Venus, with an iron core making up around 26% of its total mass, though with a large uncertainty of ±20%.

Reader's Guide

Kepler-93b's significance lies in its record-setting radius precision, which set a benchmark for exoplanet characterization in 2014. The 1.3% uncertainty in its radius allowed astronomers to tightly constrain its composition, revealing a rocky world with an iron core fraction comparable to that of Earth and Venus. Its high density, revised upward in 2023 to 7.93 g/cm³, reinforces its classification as a dense Super-Earth. The planet orbits extremely close to its host star—every 4.73 days at 0.05343 AU—resulting in an equilibrium temperature of 1133 K, hot enough to melt aluminum. Kepler-93b also shares its system with a non-transiting companion, Kepler-93c, likely a brown dwarf with a much wider orbit, though its precise nature remains uncertain. The planet is often compared to other dense close-in Super-Earths such as CoRoT-7b, HD 219134 b, Kepler-10b, and Kepler-36b, which have similar radii, masses, or temperatures.

Did You Know?

• Kepler-93b's radius was measured with a margin of error of just 1.3% in July 2014, the most precise exoplanet radius measurement at the time.
• The planet's density of 7.93 g/cm³ is roughly the same as that of metallic iron.
• Its equilibrium temperature of 1133 K is above the melting point of aluminum.
• The host star Kepler-93 is 6.6 billion years old, about 2 billion years older than the Sun.