Kepler-9c
Encyclopedia
Kepler-9c is one of the first seven extrasolar planets, exoplanets, discovered by NASA's Kepler Mission
, and one of at least two planets orbiting the star Kepler-9
. Kepler-9c and Kepler-9b
were the first exoplanets confirmed to be transiting their star. The planet's discovery was announced by the Kepler Mission
team on August 26, 2010 after its initial discovery by Kepler. At the time, it was one of 700 planetary candidates noted by Kepler.
Observations of the planet have suggested that it is a hydrogen–helium gas giant that is slightly smaller than Saturn
, and that it orbits nearby its star at .225 AU
. Kepler-9c and b are notable in that the planets share a pattern of orbital resonance
, in which the orbit of each planet stabilizes the orbit of the other. During the time it was observed by the spacecraft, the planet's orbit, which lasts on average approximately 38 days, shortened by 39 minutes every orbital period
because of this effect. Its orbit, over time, oscillates slightly above and below a 2:1 ratio with planet b.
. Kepler-9 itself was named after the Kepler Mission
, a NASA
project oriented towards discovering planets that are transiting their home stars.
The planet was one of 700 planetary candidates considered by Kepler in its first 43 days of operation. It was highlighted as a part of one of five star systems that seemed to hold multiple transiting planets. Kepler-9c and Kepler-9b
were confirmed as the first planets discovered to transit the same star.
Initial estimates concerning Kepler-9c's mass were refined by follow-up observations made by the Keck 1 Telescope at the W.M. Keck Observatory at Mauna Kea
, Hawaii
. Keck was able to confirm that Kepler-9c and Kepler-9b were planets that were slightly smaller than planet Saturn
.
. It is approximately .171 MJ
, or 17% the mass of planet Jupiter
. It also has a radius of .823 RJ, which makes it slightly smaller (1.5%) than Saturn. The planet is, on average, situated .225 AU
from the star.
It is probable that the planet is composed of hydrogen
and helium
. The planet orbits on the same plane as Kepler-9b
, a second and larger gas giant located in the Kepler-9
system. While observing the planet, the Kepler team noticed that Kepler-9b and c orbited in a 1:2 ratio, where Kepler-9b orbits its star every 19 days and Kepler-9c orbits every 38 days. The gravitational pull that each planet has on the other, known as orbital resonance
, keeps the planets in a stable orbit. This phenomenon is the first of its kind seen outside the Solar System. Every time Kepler-9c completed an orbit during the observation period, its orbital period decreased by about 39 minutes. At some point, however, this trend will reverse and its orbit will increase. The lengths of its orbit will oscillate slightly above and below the 2:1 ratio.
Kepler Mission
The Kepler spacecraft is an American space observatory, the space-based portion of NASA's Kepler Mission to discover Earth-like planets orbiting other stars. The spacecraft is named in honor of the 17th-century German astronomer Johannes Kepler...
, and one of at least two planets orbiting the star Kepler-9
Kepler-9
Kepler-9 is a sunlike star in the constellation Lyra. It is situated in the Kepler Mission's field of view. Kepler-9 has three confirmed extrasolar planets, all discovered by Kepler using the transit method. The discovery of the first two planets was announced on August 26, 2010, and of the third...
. Kepler-9c and Kepler-9b
Kepler-9b
Kepler-9b is one of the first planets discovered outside the solar system by NASA's Kepler Mission. It revolves around the star Kepler-9 within the constellation Lyra. Kepler-9b is the largest of three planets detected in the Kepler system by transit method; its mass is slightly smaller than the...
were the first exoplanets confirmed to be transiting their star. The planet's discovery was announced by the Kepler Mission
Kepler Mission
The Kepler spacecraft is an American space observatory, the space-based portion of NASA's Kepler Mission to discover Earth-like planets orbiting other stars. The spacecraft is named in honor of the 17th-century German astronomer Johannes Kepler...
team on August 26, 2010 after its initial discovery by Kepler. At the time, it was one of 700 planetary candidates noted by Kepler.
Observations of the planet have suggested that it is a hydrogen–helium gas giant that is slightly smaller than Saturn
Saturn
Saturn is the sixth planet from the Sun and the second largest planet in the Solar System, after Jupiter. Saturn is named after the Roman god Saturn, equated to the Greek Cronus , the Babylonian Ninurta and the Hindu Shani. Saturn's astronomical symbol represents the Roman god's sickle.Saturn,...
, and that it orbits nearby its star at .225 AU
Astronomical unit
An astronomical unit is a unit of length equal to about or approximately the mean Earth–Sun distance....
. Kepler-9c and b are notable in that the planets share a pattern of orbital resonance
Orbital resonance
In celestial mechanics, an orbital resonance occurs when two orbiting bodies exert a regular, periodic gravitational influence on each other, usually due to their orbital periods being related by a ratio of two small integers. Orbital resonances greatly enhance the mutual gravitational influence of...
, in which the orbit of each planet stabilizes the orbit of the other. During the time it was observed by the spacecraft, the planet's orbit, which lasts on average approximately 38 days, shortened by 39 minutes every orbital period
Orbital period
The orbital period is the time taken for a given object to make one complete orbit about another object.When mentioned without further qualification in astronomy this refers to the sidereal period of an astronomical object, which is calculated with respect to the stars.There are several kinds of...
because of this effect. Its orbit, over time, oscillates slightly above and below a 2:1 ratio with planet b.
Nomenclature and history
As with most exoplanets, the name "Kepler-9c" denotes that it is the second planet discovered in the orbit of the star Kepler-9Kepler-9
Kepler-9 is a sunlike star in the constellation Lyra. It is situated in the Kepler Mission's field of view. Kepler-9 has three confirmed extrasolar planets, all discovered by Kepler using the transit method. The discovery of the first two planets was announced on August 26, 2010, and of the third...
. Kepler-9 itself was named after the Kepler Mission
Kepler Mission
The Kepler spacecraft is an American space observatory, the space-based portion of NASA's Kepler Mission to discover Earth-like planets orbiting other stars. The spacecraft is named in honor of the 17th-century German astronomer Johannes Kepler...
, a NASA
NASA
The National Aeronautics and Space Administration is the agency of the United States government that is responsible for the nation's civilian space program and for aeronautics and aerospace research...
project oriented towards discovering planets that are transiting their home stars.
The planet was one of 700 planetary candidates considered by Kepler in its first 43 days of operation. It was highlighted as a part of one of five star systems that seemed to hold multiple transiting planets. Kepler-9c and Kepler-9b
Kepler-9b
Kepler-9b is one of the first planets discovered outside the solar system by NASA's Kepler Mission. It revolves around the star Kepler-9 within the constellation Lyra. Kepler-9b is the largest of three planets detected in the Kepler system by transit method; its mass is slightly smaller than the...
were confirmed as the first planets discovered to transit the same star.
Initial estimates concerning Kepler-9c's mass were refined by follow-up observations made by the Keck 1 Telescope at the W.M. Keck Observatory at Mauna Kea
Mauna Kea
Mauna Kea is a volcano on the island of Hawaii. Standing above sea level, its peak is the highest point in the state of Hawaii. However, much of the mountain is under water; when measured from its oceanic base, Mauna Kea is over tall—significantly taller than Mount Everest...
, Hawaii
Hawaii
Hawaii is the newest of the 50 U.S. states , and is the only U.S. state made up entirely of islands. It is the northernmost island group in Polynesia, occupying most of an archipelago in the central Pacific Ocean, southwest of the continental United States, southeast of Japan, and northeast of...
. Keck was able to confirm that Kepler-9c and Kepler-9b were planets that were slightly smaller than planet Saturn
Saturn
Saturn is the sixth planet from the Sun and the second largest planet in the Solar System, after Jupiter. Saturn is named after the Roman god Saturn, equated to the Greek Cronus , the Babylonian Ninurta and the Hindu Shani. Saturn's astronomical symbol represents the Roman god's sickle.Saturn,...
.
Characteristics
Kepler-9c is a gas giant that is smaller and slightly less massive than planet SaturnSaturn
Saturn is the sixth planet from the Sun and the second largest planet in the Solar System, after Jupiter. Saturn is named after the Roman god Saturn, equated to the Greek Cronus , the Babylonian Ninurta and the Hindu Shani. Saturn's astronomical symbol represents the Roman god's sickle.Saturn,...
. It is approximately .171 MJ
Jupiter mass
Jupiter mass , is the unit of mass equal to the total mass of the planet Jupiter . Jupiter mass is used to describe masses of the gas giants, such as the outer planets and extrasolar planets. It is also used in describing brown dwarfs....
, or 17% the mass of planet Jupiter
Jupiter
Jupiter is the fifth planet from the Sun and the largest planet within the Solar System. It is a gas giant with mass one-thousandth that of the Sun but is two and a half times the mass of all the other planets in our Solar System combined. Jupiter is classified as a gas giant along with Saturn,...
. It also has a radius of .823 RJ, which makes it slightly smaller (1.5%) than Saturn. The planet is, on average, situated .225 AU
Astronomical unit
An astronomical unit is a unit of length equal to about or approximately the mean Earth–Sun distance....
from the star.
It is probable that the planet is composed of hydrogen
Hydrogen
Hydrogen is the chemical element with atomic number 1. It is represented by the symbol H. With an average atomic weight of , hydrogen is the lightest and most abundant chemical element, constituting roughly 75% of the Universe's chemical elemental mass. Stars in the main sequence are mainly...
and helium
Helium
Helium is the chemical element with atomic number 2 and an atomic weight of 4.002602, which is represented by the symbol He. It is a colorless, odorless, tasteless, non-toxic, inert, monatomic gas that heads the noble gas group in the periodic table...
. The planet orbits on the same plane as Kepler-9b
Kepler-9b
Kepler-9b is one of the first planets discovered outside the solar system by NASA's Kepler Mission. It revolves around the star Kepler-9 within the constellation Lyra. Kepler-9b is the largest of three planets detected in the Kepler system by transit method; its mass is slightly smaller than the...
, a second and larger gas giant located in the Kepler-9
Kepler-9
Kepler-9 is a sunlike star in the constellation Lyra. It is situated in the Kepler Mission's field of view. Kepler-9 has three confirmed extrasolar planets, all discovered by Kepler using the transit method. The discovery of the first two planets was announced on August 26, 2010, and of the third...
system. While observing the planet, the Kepler team noticed that Kepler-9b and c orbited in a 1:2 ratio, where Kepler-9b orbits its star every 19 days and Kepler-9c orbits every 38 days. The gravitational pull that each planet has on the other, known as orbital resonance
Orbital resonance
In celestial mechanics, an orbital resonance occurs when two orbiting bodies exert a regular, periodic gravitational influence on each other, usually due to their orbital periods being related by a ratio of two small integers. Orbital resonances greatly enhance the mutual gravitational influence of...
, keeps the planets in a stable orbit. This phenomenon is the first of its kind seen outside the Solar System. Every time Kepler-9c completed an orbit during the observation period, its orbital period decreased by about 39 minutes. At some point, however, this trend will reverse and its orbit will increase. The lengths of its orbit will oscillate slightly above and below the 2:1 ratio.