Kepler-296e
A super-Earth in the habitable zone of Kepler-296.
Kepler-296e is a confirmed super-Earth exoplanet orbiting within the habitable zone of the star Kepler-296. It was discovered by NASA's Kepler spacecraft using the transit method, and its discovery was announced on 26 February 2014.
Quick Facts
- Discovery Site
- Kepler Space Observatory
- Discovered
- 2014
- Discovery Method
- Transit
- Apsis
- astron
- Semimajor
- 0.17400 AU
- Period
- 34.14234700 d
- Eccentricity
- <0.33
- Inclination
- 89.950
- Star
- Kepler-296
- Single Temperature
- 267 K
Facts from the source article.
Lore & Background
Kepler-296e was initially assumed to be a super-Earth with a radius 1.75 times that of Earth, but a revised estimate placed it at 1.53 Earth radii. Its mass is estimated at 4.52 Earth masses under a higher-than-Earth density assumption, or 3.58 Earth masses assuming an Earth-like density. The planet orbits its star every 34.1 days at a distance of 0.169 AU, and its equilibrium temperature of 267 K is much higher than Earth's. The planet is likely rocky due to its relatively low radius, in contrast to the larger Kepler-296f. It receives 1.4 times Earth's solar flux, placing it well within the habitable zone and just beyond the runaway greenhouse line. According to Kopparapu et al. (2013), it lies within the most conservative boundaries of the habitable zone. However, its orbit is eccentric, with a maximum eccentricity of 0.33 at 3-sigma confidence. The planet's equilibrium temperature varies with albedo and tidal locking: for a non-tidally locked planet with an Earth-like albedo of 0.3, it is 234 K; for a Venus-like albedo of 0.7, it is 189 K; and for a tidally locked planet with an Earth-like albedo of 0.3, it is 278 K. Tidal locking may not have occurred due to the planet's likely eccentric orbit, as an Earth-size planet with eccentricity less than 0.1 and no moons orbiting within the habitable zone of a star with mass less than 0.42 solar masses would be tidally locked, but Kepler-296e's orbit is more eccentric than that modeled fictional planet.
Reader's Guide
Kepler-296e is notable as a confirmed super-Earth located within the habitable zone of its star, where liquid water could exist on its surface. As of 2017, it held an Earth Similarity Index of 0.85, making it the fifth-most Earth-like planet known at that time, after Kepler-438b, TRAPPIST-1 d, GJ 3323 b, and Gliese 273 b (Luyten b). Its discovery by NASA's Kepler spacecraft using the transit method contributed to the growing catalog of potentially habitable exoplanets. The planet's relatively low radius suggests a rocky composition, and its position within the conservative habitable zone boundaries, as defined by Kopparapu et al. (2013), underscores its significance in the search for worlds that could support life. However, its eccentric orbit introduces variability in its equilibrium temperature, which could affect its habitability. The planet's legacy lies in its role as a benchmark for Earth-like exoplanets and in informing models of tidal locking and habitable zone boundaries for red dwarf systems.
Frequently Asked Questions
What is Kepler-296e?
Kepler-296e is a confirmed super-Earth exoplanet that orbits the star Kepler-296 within its habitable zone. NASA's Kepler space telescope identified it, and the discovery was made public on 26 February 2014.
How big and heavy is Kepler-296e?
Its radius is estimated between 1.53 and 1.75 Earth radii, with a mass in the range of 3.58 to 4.52 Earth masses. The planet completes one full orbit every 34.1 days at a semimajor axis of 0.169 AU.
How was Kepler-296e detected?
The Kepler spacecraft used the transit method, watching for the subtle dimming of starlight as the planet crosses in front of its host star. The resulting signal was confirmed and announced in February 2014.
Could liquid water exist on Kepler-296e?
Its equilibrium temperature of roughly 267 K (about –6 °C) places it squarely inside the habitable zone, and its Earth Similarity Index of 0.85 underscores how closely its conditions mirror Earth's. Whether water actually persists, of course, depends on the planet's unknown atmospheric makeup.
Why does Kepler-296e matter to the exoplanet community?
It is one of the more Earth-like super-Earths confirmed in a habitable zone, giving researchers a concrete target for follow-up atmospheric studies. As a transit-detected world with a near-0.85 ESI, it strengthens the growing evidence that temperate rocky planets are common around main-sequence stars.
More in Transiting Exoplanets, Part 3 1-24
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