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In celestial mechanics, orbital resonance occurs when orbiting bodies exert regular, periodic gravitational influence on each other, usually because their orbital periods are related by a ratio of small integers. Most commonly, this relationship is found between a pair of objects. The physical principle behind orbital resonance is similar in concept to pushing a child on a swing, whereby the orbit and the swing both have a natural frequency, and the body doing the "pushing" will act in periodic repetition to have a cumulative effect on the motion. Orbital resonances greatly enhance the mutual gravitational influence of the bodies. In most cases, this results in an unstable interaction, in which the bodies exchange momentum and shift orbits until the resonance no longer exists. Under some circumstances, a resonant system can be self-correcting and thus stable. Examples are the 1:2:4 resonance of Jupiter's moons Ganymede, Europa and Io, and the 2:3 resonance between Neptune and Pluto. Unstable resonances with Saturn's inner moons give rise to gaps in the rings of Saturn. The special case of 1:1 resonance between bodies with similar orbital radii causes large planetary system bodies to eject most other bodies sharing their orbits; this is part of the much more extensive process of clearing the neighbourhood, an effect that is used in the current definition of a planet.
K2-3, also known as EPIC 201367065, is a red dwarf star with three known planets. It is on the borderline of being a late orange dwarf/K-type star, but because of its temperature, it is classified as a red dwarf.
K2-3b, also known as EPIC 201367065 b, is an exoplanet orbiting the red dwarf K2-3 every 10 days. It is the largest and most massive planet of the K2-3 system, with about 2.1 times the radius of Earth and about 5 times the mass. Its density of about 3.1 g/cm3 may indicate a composition of almost entirely water, or a hydrogen envelope comprising about 0.7% of the planet's mass.
K2-3c, also known as EPIC 201367065 c, is an exoplanet orbiting the red dwarf star K2-3 every 24 days. It is 143 light-years away. It has a density of about 3.7 g/cm3, indicating that it could be an ocean world or a mini-Neptune. It is the second-smallest planet in the system by both radius and mass, with a mass almost three times that of Earth.
K2-3d, also known as EPIC 201367065 d, is a confirmed exoplanet of probable mini-Neptune type orbiting the red dwarf star K2-3, and the outermost of three such planets discovered in the system. It is located 143 light-years away from Earth in the constellation of Leo. 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. It was the first planet in the Kepler "Second Light" mission to receive the letter "d" designation for a planet. Its discovery was announced in January 2015.
K2-24b also known as EPIC 203771098 b is an exoplanet orbiting the Sun-like star K2-24 every 21 days. It has about the same density as Saturn, at 0.7103 g/cm3, which indicates that the planet is clearly a gas giant.
K2-72 is a cool red dwarf star of spectral class M2.7V located about 217 light-years away from the Earth in the constellation of Aquarius. It is known to host four planets, all similar in size to Earth, with one of them residing within the habitable zone.
K2-72e (also known by its EPIC designation EPIC 206209135.04), is a confirmed exoplanet, likely rocky, orbiting within the habitable zone of the red dwarf star K2-72, the outermost of four such planets discovered in the system by NASA's Kepler spacecraft on its "Second Light" mission. It is located about 217.1 light-years (66.56 parsecs, or nearly 2.0538×1015 km) away from Earth in the constellation of Aquarius. 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.
WASP-47 is a star similar in size and brightness to the Sun about 870 light-years away in the constellation Aquarius. It lies within the Kepler K2 campaign field 3. It was first noticed to have a hot Jupiter exoplanet orbiting every 4 days in 2012 by the Wide Angle Search for Planets (WASP) team. While it was thought to be a typical hot Jupiter system, three more planets were found in 2015: an outer gas giant within the habitable zone, a hot Neptune exterior to the hot Jupiter's orbit and a super-Earth interior to the hot Jupiter's orbit. WASP-47 is the only planetary system known to have both planets near the hot Jupiter and another planet much further out.
K2-138, also designated EPIC 245950175 or EE-1, is a large early K-type main sequence star with a system of at least 6 planets discovered by citizen scientists. Four were found in the first two days of the Exoplanet Explorers project on Zooniverse in early April 2017, while two more were revealed in further analysis. The system is about 660 light-years away in the constellation Aquarius, within K2 Campaign 12.
K2-141b is a massive rocky exoplanet orbiting extremely close to an orange main-sequence star K2-141. The planet was first discovered by the Kepler space telescope during its K2 “Second Light” mission and later observed by the HARPS-N spectrograph. It is classified as an Ultra-short Period (USP) and is confirmed to be terrestrial in nature. Its high density implies a massive iron core taking up between 30% and 50% of the planet's total mass.
K2-229b is an extremely hot, solid, iron-rich exoplanet in a close orbit around the active K-dwarf K2-229 in the constellation Virgo, 335 light years away from Earth.
K2-239 is a small red dwarf star in the constellation Sextans, about 49 parsecs away from Earth. Observed by the Kepler Space Telescope during Campaign 14 of its K2 "Second Light" mission, it was found to have three hot, likely rocky Earth-sized planets in orbit around it.
K2-236b is a Neptune-like exoplanet that orbits an F-type star. It is also called EPIC 211945201 b. Its mass is 27 Earths, it takes 19.5 days to complete one orbit of its star, and is 0.148 AU from its star. Its discovery was announced in 2018. This was the first exoplanet discovered by scientists based in India. The discoverers were Abhijit Chakraborty (PRL), Arpita Roy (Caltech), Rishikesh Sharma (PRL), Suvrath Mahadevan, Priyanka Chaturvedi, Neelam J.S.S.V Prasad (PRL), and B. G. Anandarao (PRL).
HD 89345 b is a Neptune-like exoplanet that orbits a G-type star. It is also called K2-234b. Its mass is 35.7 Earths, it takes 11.8 days to complete one orbit of its star, and is 0.105 AU from its star. It was discovered by 43 astrophysicists, one which is V. Van Eylen, and is announced in 2018.
HATS-36b is a gas giant exoplanet that orbits an F-type star. Its mass is 3.216 Jupiters, it takes 4.2 days to complete one orbit of its star, and is 0.05425 AU from it. It was discovered on June 12, 2017 and was announced in 2018. Its discoverers were 23, namely Daniel Bayliss, Joel Hartman, George Zhou, Gaspar Á. Bakos, Andrew Vanderburg, J. Bento, L. Mancini, S. Ciceri, Rafael Brahm, Andres Jordán, N. Espinoza, M. Rabus, T. G. Tan, K. Penev, W. Bhatti, M. de Val-Borro, V. Suc, Z. Csubry, Th. Henning, P. Sarkis, J. Lázár, I. Papp, P. Sári.
K2-288Bb is a super-Earth or mini-Neptune exoplanet orbiting in the habitable zone of K2-288B, a low-mass M-dwarf star in a binary star system in the constellation of Taurus about 226 light-years from Earth. It was discovered by citizen scientists while analysing data from the Kepler spacecraft's K2 mission, and was announced on 7 January 2019. K2-288 is the third transiting planet system identified by the Exoplanet Explorers program, after the six planets of K2-138 and the three planets of K2-233.
K2-32 is a G9-type main sequence star slightly smaller and less massive than the sun. Four confirmed transiting exoplanets are known to orbit this star. A study of atmospheric escape from the planet K2-32b caused by high-energy stellar irradiation indicates that the star has always been a very slow rotator.
K2-24 is a metal-rich G3-type main sequence star larger and more massive than the Sun, located 560 light-years away in the constellation Scorpius. Two confirmed transiting exoplanets are known to orbit this star. An attempt to detect stellar companions using adaptive optics imaging at the Keck telescope was negative however later observations using lucky imaging at the Danish 1.54 m telescope at La Silla Observatory detected a possible companion at 3.8 arcseconds distance from K2-24. This candidate companion being over 8 magnitudes fainter than K2-24 and with a color temperature of 5400 Kelvin, is inconsistent with a bound main sequence companion.
References
- 1 2 3 4 5 6 "Planet EPIC 2037 b". Extrasolar Planets Encyclopaedia . Archived from the original on 2015-11-24. Retrieved 2015-10-17.
- 1 2 3 4 Petigura, Erik A.; et al. (14 November 2015). "Two Transiting Low Density Sub-Saturns from K2". The Astrophysical Journal. 818 (1): 36. arXiv: 1511.04497 . Bibcode:2016ApJ...818...36P. doi: 10.3847/0004-637X/818/1/36 . S2CID 23452646.
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