Kepler-438b

Kepler-438b

Exoplanet		List of exoplanets
Approximate size comparison of Kepler-438b (right) with Earth
Parent star
Star		Kepler-438
Constellation		Lyra
Right ascension	(α)	18h 46m 35.000s
Declination	(δ)	+41° 57′ 3.93″
Apparent magnitude	(mV)	14.467
Distance		470; 475 ly (145 pc)
Mass	(m)	0.540 M☉
Radius	(r)	0.520 R☉
Temperature	(T)	3748 K
Metallicity	[Fe/H]	0.160
Age		4.4+0.8 −0.7 Gyr
Physical characteristics
Radius	(r)	1.120 R⊕
Stellar flux	(F⊙)	1.40+0.67 −0.77 ⊕
Temperature	(T)	276 K (3 °C; 37 °F)
Orbital elements
Semi-major axis	(a)	0.16600 AU
Eccentricity	(e)	0.03+0.01 −0.03
Orbital period	(P)	35.23319000 d
Inclination	(i)	89.860°
Discovery information
Discovery date		2015
Discoverer(s)
Discovery method		Transit
Discovery site		Kepler Space Observatory
Discovery status		Published refereed article
Other designations
KOI-3284.01; Kepler-438 b; KOI-3284 b; K03284.01; WISE J184634.98+415704.0 b; KIC 6497146 b; 2MASS J18463499+4157039 b
Database references
Extrasolar Planets Encyclopaedia		data
SIMBAD		data
Exoplanet Archive		data
Open Exoplanet Catalogue		data

Kepler-438b (also known by its Kepler Object of Interest designation KOI-3284.01) is a confirmed near-Earth-sized exoplanet, likely rocky, orbiting within the habitable zone of the red dwarf Kepler-438, about 470 light-years (145 pc) from Earth in the constellation Lyra. The planet was discovered by NASA's Kepler spacecraft using the transit method, in which the dimming effect that a planet causes as it crosses in front of its star is measured. NASA announced the confirmation of the exoplanet on 6 January 2015. Although it is not habitable, as of June 2015, it is the most Earth-like exoplanet.

Kepler-438b is approximately 470 light years from Earth, so travelling there is presently impossible within a human lifetime. The German-designed Helios probes, notable for having set the current speed record among spacecraft at 252,792 km/h, would take some two million years to travel to Kepler-438b.

Basic data

Kepler-438b is a near-Earth-sized exoplanet with a radius 1.12 times that of Earth. The planet orbits the red dwarf Kepler-438, a star considerably smaller and cooler than the Sun, once every 35.2 days.

Habitability

The planet was announced as orbiting within the habitable zone of Kepler-438, a region where liquid water could exist on the surface of the planet. In the Earth Similarity Index (ESI), which measures how similar are planets to Earth as to physics and chemistry, with 1.00 being the most similar, Kepler-438b has an index of 0.88, the highest known to date, making it currently the most Earth-like planet. However it has been found that this planet is subjected to superflare activity from its parent star every 100 days, much more violent storms than the stellar flares emitted by the Sun and which would be capable of sterilizing life on Earth.

Researchers at the University of Warwick say that Kepler-438b is not habitable after all due to the large amount of radiation it receives. The question of what makes a planet habitable is much more complex than having a planet located at the right distance from its host star so that water can be liquid on its surface: various geophysical and geodynamical aspects, the radiation, and the host stars plasma environment can influence the evolution of planets and life, if it originated.

Notable Exoplanets – Kepler Space Telescope
Confirmed small exoplanets in habitable zones. (Kepler-62e, Kepler-62f, Kepler-186f, Kepler-296e, Kepler-296f, Kepler-438b, Kepler-440b, Kepler-442b) (Kepler Space Telescope; 6 January 2015).

See also

• Kepler-442b
• Kepler-452b
• Habitability of red dwarf systems
• List of potentially habitable exoplanets

External links

• NASA – Kepler Mission.
• NASA – Kepler Discoveries – Summary Table.
• NASA – Kepler-438b at The NASA Exoplanet Archive.
• NASA – Kepler-438b at The Extrasolar Planets Encyclopaedia.
• Habitable Exolanets Catalog at UPR-Arecibo.

Preceded by Gliese 667 Cc

Highest ESI for an exoplanet 2015 — present

Succeeded by none