Last updated
Exoplanet List of exoplanets
Parent star
Star Kepler-1229 (KOI-2418)
Constellation Cygnus
Right ascension (α)19h 49m 56.8076s [1]
Declination (δ)+46° 59 48.1073 [1]
Apparent magnitude (mV)15.474
Distance 870±10 [1]   ly
(267±3 [1]   pc)
Spectral type M?V [2]
Mass (m)0.54 (± 0.3) [3]   M
Radius (r)0.51 (± 0.03) [3]   R
Temperature (T)3784 (± 39) [3]   K
Metallicity [Fe/H]−0.06 (± 0.1) [3]
Age 3.72+5.32
[3]   Gyr
Physical characteristics
Mass (m)~2.7 [4] M
Radius (r)1.40+0.11
[3] [nb 1] R
Stellar flux (F)0.35+0.12
Temperature (T)213 K (−60 °C; −76 °F)
Orbital elements
Semi-major axis (a)0.2896 [nb 2] AU
Eccentricity (e)~0
Orbital period (P)86.829 [5] d
Inclination (i)~89.5°
Discovery information
Discovery dateMay 12, 2016
Discoverer(s) Kepler spacecraft
Discovery method transit
Discovery statusPublished
Other designations
WISE J194956.83+465948.1 b, K02418.01, 2MASS J19495680+4659481 b, KOI-2418.01, KOI-2418 b, KIC 10027247 b
Database references
Extrasolar Planets
Exoplanet Archive data
Open Exoplanet Catalogue data

Kepler-1229b [5] (also known by its Kepler Object of Interest designation KOI-2418.01) is a confirmed super-Earth exoplanet, likely rocky, orbiting within the habitable zone of the red dwarf star Kepler-1229, located about 870 light years (267 parsecs from Earth in the constellation of Cygnus. [6] [3] It was discovered in 2016 by the Kepler space telescope. [7] The exoplanet was found by using the transit method, in which the dimming effect that a planet causes as it crosses in front of its star is measured.



Mass, radius and temperature

Kepler-1229b is likely a rocky super-Earth, an exoplanet with a radius and mass bigger than Earth, but smaller than that of the gas giants Neptune and Uranus. It has an equilibrium temperature of 213 K (−60 °C; −76 °F). [4] Kepler-1229b's mass is not known, but based on its radius, it is likely to be in the range of about 2.7 M, based on its composition. [4]

Host star

The planet orbits a (M-type) star named Kepler-1229, orbited by a total of one planet. The star has a mass of 0.54 M and a radius of 0.51 R. It has a temperature of 3724 K and is about 3.72 billion years old. [3] In comparison, the Sun is 4.6 billion years old [8] and has a temperature of 5778 K. [9]

The star's apparent magnitude, or how bright it appears from Earth's perspective, is 15.474. Therefore, it is too dim to be seen with the naked eye.


Kepler-1229b orbits its host star with about 4% of the Sun's luminosity every 86.829 days at a distance of 0.2896  AU (close to that of Mercury, which orbits at a distance of 0.387 AU).


The exoplanet, along with eight others, was announced to be orbiting in the habitable zone of its parent star, the region where, with the correct conditions and atmospheric properties, liquid water may exist on the surface of the planet. [7] Kepler-1229b has a radius of 1.4 R, so it is likely rocky. Its host star is a red dwarf, with about half as much mass than the Sun does. As a result, stars like Kepler-1229 have the ability to live up to 50–60 billion years, 5–6 times longer than the Sun will live. [10]

The planet is likely tidally locked, with one side of its hemisphere permanently facing towards the star, while the opposite side shrouded in eternal darkness. However, between these two intense areas, there would be a sliver of habitability – called the terminator line, where the temperatures may be suitable (about 273 K (0 °C; 32 °F)) for liquid water to exist. Additionally, a much larger portion of the planet may be habitable if it supports a thick enough atmosphere to transfer heat to the side facing away from the star.

Discovery and follow-up studies

In 2013, before the two wheels failed, NASA's Kepler spacecraft was completing observing stars on its photometer, the instrument it uses to detect transit events, in which a planet crosses in front of and dims its host star for a brief and near-regular period of time. In this last test, Kepler observed 50000 stars in the Kepler Input Catalog, including Kepler-1229; the preliminary light curves were sent to the Kepler science team for analysis, who chose obvious planetary companions from the bunch for follow-up at observatories. The radial velocity observations confirmed that a planetary body was responsible for the dips observed in Kepler-1229's light curve, thus confirming it as a planet. The planet was then announced in the newest catalog released by NASA on May 12, 2016, about 3 years later. [11]

At nearly 770 light-years (236 pc) distant, Kepler-1229b is too remote and its star too far for current telescopes or the next generation of planned telescopes to determine its mass or whether it has an atmosphere. The Kepler spacecraft focused on a single small region of the sky but next-generation planet-hunting space telescopes, such as TESS and CHEOPS, will examine nearby stars throughout the sky. Nearby stars with planets can then be studied by the upcoming James Webb Space Telescope and future large ground-based telescopes to analyze atmospheres, determine masses and infer compositions. Additionally the Square Kilometer Array would significantly improve radio observations over the Arecibo Observatory and Green Bank Telescope. [12]

See also


  1. The 1.40 Earth radius was taken from a data set of confirmed Kepler planets, updated by NASA in 10 May 2016. The Morton et al. 2016 (version 1) paper actually used an older data set for Kepler candidate planets that, at the time, was only updated back in 18 September 2015 but that data set gave a different value of 1.12 Earth radius for the planet, along with different mass, radius and temperature for the star.
  2. Kepler's Third Law, assuming a circular orbit: Mass and the period are known, so the equation can be written with semimajor axis as the subject: .


  1. 1 2 3 4 Brown, A. G. A.; et al. (Gaia collaboration) (August 2018). "Gaia Data Release 2: Summary of the contents and survey properties". Astronomy & Astrophysics . 616. A1. arXiv: 1804.09365 . Bibcode: 2018A&A...616A...1G . doi: 10.1051/0004-6361/201833051 . Gaia DR2 record for this source at VizieR.
  3. 1 2 3 4 5 6 7 8 "Kepler-1229 b". NASA Exoplanet Science Institute. 10 May 2016. Retrieved 2016-05-11.
  4. 1 2 3 "The Habitable Exoplanets Catalog - Planetary Habitability Laboratory @ UPR Arecibo" . Retrieved 27 June 2016.
  5. 1 2 3 Morton, Timothy D.; Bryson, Stephen T.; Coughlin, Jeffrey L.; Rowe, Jason F.; Ravichandran, Ganesh; Petigura, Erik A.; Haas, Michael R.; Batalha, Natalie M (10 May 2016). "False positive probabilities for all Kepler Objects of Interest: 1284 newly validated planets and 428 likely false positives". The Astrophysical Journal. 822 (2): 86. arXiv: 1605.02825 . Bibcode:2016ApJ...822...86M. doi:10.3847/0004-637X/822/2/86.
  6. Prostak, Sergio (11 May 2016). "Astronomers Confirm 1,284 New Kepler Exoplanets". NASA. Sci News. Retrieved 2016-05-11.
  7. 1 2 1st Alien Earth Still Elusive Despite Huge Exoplanet Haul, Mike Wall,
  8. Fraser Cain (16 September 2008). "How Old is the Sun?". Universe Today . Retrieved 19 February 2011.
  9. Fraser Cain (15 September 2008). "Temperature of the Sun". Universe Today. Retrieved 19 February 2011.
  10. Adams, Fred C.; Laughlin, Gregory; Graves, Genevieve J. M. "Red Dwarfs and the End of the Main Sequence". Gravitational Collapse: From Massive Stars to Planets. Revista Mexicana de Astronomía y Astrofísica. pp. 46–49. Bibcode:2004RMxAC..22...46A.
  11. Northon, Karen (10 May 2016). "Kepler Mission Announces Largest Planet Collection Ever Discovered" . Retrieved 27 June 2016.
  12. Siemion, Andrew P.V.; Demorest, Paul; Korpela, Eric; Maddalena, Ron J.; Werthimer, Dan; Cobb, Jeff; Langston, Glen; Lebofsky, Matt; Marcy, Geoffrey W.; Tarter, Jill (3 February 2013). "A 1.1 to 1.9 GHz SETI Survey of the Kepler Field: I. A Search for Narrow-band Emission from Select Targets". Astrophysical Journal. 767 (1): 94. arXiv: 1302.0845 . Bibcode:2013ApJ...767...94S. doi:10.1088/0004-637X/767/1/94.

Coordinates: 19h 49m 56.81s, +46° 59′ 48.2″