Kepler-11f

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Kepler-11f
Exoplanet Comparison Kepler-11 f.png
Size comparison of Kepler-11f (gray) with Neptune and Earth.
Discovery
Discovery date2 February 2011 [1]
Transit (Kepler Mission) [1]
Orbital characteristics
0.25 AU (37,000,000 km)
46.68876 [2] d
Inclination 89.4 [2]
Star Kepler-11 (KOI-157)
Physical characteristics
Mean radius
2.61 ± 0.25 [3] R🜨
Mass 2.3 +2.2
1.2
[3] M🜨
Mean density
0.7 +0.7
0.4
[3] g cm−3
Temperature 544 K (271 °C; 520 °F) [2]

    Kepler-11f is an exoplanet (extrasolar planet) discovered in the orbit of the sun-like star Kepler-11 by NASA's Kepler spacecraft, which searches for planets that transit (cross in front of) their host stars. Kepler-11f is the fifth planet from its star, orbiting one quarter of the distance (.25 AU) of the Earth from the Sun every 47 days. It is the furthest of the first five planets in the system. Kepler-11f is the least massive of Kepler-11's six planets, at nearly twice the mass of Earth; it is about 2.6 times the radius of Earth. Along with planets d and e and unlike the two inner planets in the system, Kepler-11f has a density lower than that of water and comparable to that of Saturn. This suggests that Kepler-11f has a significant hydrogen–helium atmosphere. [1] The Kepler-11 planets constitute the first system discovered with more than three transiting planets. [1] Kepler-11f was announced to the public on February 2, 2011, after follow-up investigations at several observatories. [4] Analysis of the planets and study results were published the next day in the journal Nature . [1]

    Contents

    Name and discovery

    Kepler-11, known as KOI-157 when it was first flagged for a transit event, [2] is the planet's host star, and it is included in the planet's name to denote that. Because Kepler-11f was discovered with five other planets, the planets of Kepler-11 were sorted by distance from the host star; thus, since Kepler-11f is the fifth planet from its star, it was given the letter "f." The name "Kepler" is derived from the Kepler satellite, a NASA Earth-trailing spacecraft that constantly observes a small patch of sky between the constellations Cygnus and Lyra for stars that are transited by, in particular, terrestrial planets. As these planets cross in front of their host stars with respect to Earth, a small and periodic dip in the star's brightness occurs; this dip is noted by the spacecraft and tagged for future study. Scientists then analyze the transit event more carefully to verify if the planet actually exists and to gather information on the planet's orbit and composition (if possible). [4]

    Follow-up observations were conducted at observatories at the W. M. Keck Observatory's Keck 1 telescope in Hawaii; the Shane and Hale telescopes in California; the Harlan J. Smith and Hobby–Eberly telescopes in Texas; telescopes at the WIYN (including MMT) and Whipple observatories in Arizona; and the Nordic Optical Telescope in the Canary Islands. The Spitzer Space Telescope was also used. According to NASA, Kepler-11's system is the most compact and the flattest system yet discovered, surpassing even the Solar System. [4]

    Host star

    Kepler-11 is a G-type star, [5] much like the Sun is, and is located 659 parsecs away in the Cygnus constellation. It has 95% the mass and 110% the radius of the Sun. Its mass and radius, combined with an approximate iron content (metallicity) of 0 and effective temperature of 5680 K, makes the star very similar to the Sun, though slightly more diffuse and slightly cooler. However, the star is approximately 1.74 times the age of the Sun, and is estimated to have existed for eight billion years. Kepler-11 has six known planets in orbit: Kepler-11b, Kepler-11c, Kepler-11d, Kepler-11e, Kepler-11f, and Kepler-11g. [2] Kepler-11's five inner planets orbit closely to their host star, and their orbits would fit within that of Mercury's. [1]

    With an apparent magnitude of 14.2, Kepler-11 cannot be seen with the naked eye. [2]

    Characteristics

    A comparison of the Kepler planets as compared to Earth, Jupiter, and previous Kepler finds. Kepler-11f is in pink at the bottom-right. Kepler-11 planets comparison.jpg
    A comparison of the Kepler planets as compared to Earth, Jupiter, and previous Kepler finds. Kepler-11f is in pink at the bottom-right.

    Kepler-11f is, at 2.3 times the mass of Earth, the least massive of the six planets discovered in the orbit of Kepler-11, although the planet's mass may range from 1.1 to 4.5, or from approximately that of Earth's mass to that of Kepler-10b, a rather large confidence interval. [2] Its radius is the second smallest of the six planets discovered in the system at 2.61 times the radius of Earth. Kepler-11f has a density of about 0.7 g/cm3, comparable to that of the Solar System's least dense planet, Saturn. Kepler-11f is the fifth planet from Kepler-11, orbiting its host star every 46.68876 days at a distance of 0.25 AU. Its orbital eccentricity is unknown. In comparison, Mercury orbits the Sun every 87.97 days at a distance of 0.387 AU. [6] Kepler-11f has an orbital inclination of 89.4°; it can be seen almost edge-on with respect to Earth. Its surface equilibrium temperature is 544 K, over twice the surface equilibrium temperature of Earth [2] and about two-thirds the surface temperature of Venus. [7]

    Kepler-11f's low density, characteristic of the outer planets of the system, suggests that a hydrogen–helium atmosphere is present on these planets, classifying it as "gas dwarf" due to its small size and mass. The gaseous content of the planet is calculated at a few percent of its total mass, but the envelope accounts for 70-80% of the planet's total volume. [8] Kepler-11f's low density is not shared by the planets Kepler-11b and Kepler-11c because stellar irradiation has reduced their atmospheres to a thin layer. [1] The planets accreted such atmospheres because they formed within the first few million years of the system's existence, when a protoplanetary disk was still present. [8] [9]

    Related Research Articles

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    <span class="mw-page-title-main">Kepler-10</span> Sunlike star in the constellation Draco

    Kepler-10, formerly known as KOI-72, is a Sun-like star in the constellation of Draco that lies 607 light-years from Earth. Kepler-10 was targeted by NASA's Kepler spacecraft, as it was seen as the first star identified by the Kepler mission that could be a possible host to a small, transiting exoplanet. The star is slightly less massive, slightly larger, and slightly cooler than the Sun; at an estimated 11.9 billion years in age, Kepler-10 is almost 2.6 times the age of the Sun.

    <span class="mw-page-title-main">Kepler-11</span> Sun-like star in the constellation Cygnus

    Kepler-11, also designated as 2MASS J19482762+4154328, is a Sun-like star slightly larger than the Sun in the constellation Cygnus, located some 2,150 light years from Earth. It is located within the field of vision of the Kepler spacecraft, the satellite that NASA's Kepler Mission uses to detect planets that may be transiting their stars. Announced on February 2, 2011, the star system is among the most compact and flattest systems yet discovered. It is the first discovered case of a star system with six transiting planets. All discovered planets are larger than Earth, with the larger ones being about Neptune's size.

    <span class="mw-page-title-main">Kepler-11b</span> Exoplanet orbiting Kepler-11

    Kepler-11b is an exoplanet discovered around the star Kepler-11 by the Kepler spacecraft, a NASA-led mission to discover Earth-like planets. Kepler-11b is less than about three times as massive and twice as large as Earth, but it has a lower density, and is thus most likely not of Earth-like composition. Kepler-11b is the hottest of the six planets in the Kepler-11 system, and orbits more closely to Kepler-11 than the other planets in the system. Kepler-11b, along with its five counterparts, form the first discovered planetary system with more than three transiting planets—the most densely packed known planetary system. The system is also the flattest known planetary system. The discovery of this planet and its five sister planets was announced on February 2, 2011, after follow-up investigations.

    <span class="mw-page-title-main">Kepler-11c</span> Extrasolar planet orbiting Kepler-11

    Kepler-11c is an exoplanet discovered in the orbit of the Sun-like star Kepler-11 by the Kepler spacecraft, a NASA telescope aiming to discover Earth-like planets. It is the second planet from its star, and is most likely a water planet with a thin hydrogen–helium atmosphere. Kepler-11c orbits Kepler-11 every 10 days, and has an estimated density twice that of pure water. It is estimated to have a mass thirteen times that of Earth and a radius three times that of Earth. Kepler-11c and its five sister planets form the first discovered system with more than three transiting planets. The Kepler-11 system also holds the record of being the most compact and the flattest system discovered. Kepler-11c and the other Kepler-11 planets were announced to the public on February 2, 2011, and was published in Nature a day later.

    <span class="mw-page-title-main">Kepler-11d</span> Extrasolar planet

    Kepler-11d is an exoplanet discovered in the orbit of the sun-like star Kepler-11. It is named for the telescope that discovered it, a NASA spacecraft named Kepler that is designed to detect Earth-like planets by measuring small dips in the brightness of their host stars as the planets cross in front. This process, known as the transit method, was used to note the presence of six planets in orbit around Kepler-11, of which Kepler-11d is the third from its star. Kepler-11d orbits Kepler-11 well within the orbit of Mercury approximately every 23 days. The planet is approximately six times more massive than the Earth, and has a radius that is three and a half times larger than that of Earth's. It is, however, far hotter than Earth is. Its low density, comparable to that of Saturn, suggests that Kepler-11d has a large hydrogen–helium atmosphere. Kepler-11d was announced with its five sister planets on February 2, 2011 after extensive follow-up studies.

    <span class="mw-page-title-main">Kepler-11e</span> Extrasolar planet orbiting Kepler-11

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    <span class="mw-page-title-main">Kepler-11g</span> Extrasolar planet

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    <span class="mw-page-title-main">Kepler-9d</span> Super-Earth orbiting Kepler-9

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    <span class="mw-page-title-main">Kepler-47c</span> Goldilocks gas giant orbiting Kepler-47 system

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    <span class="mw-page-title-main">Kepler-62e</span> Habitable-zone super-Earth planet orbiting Kepler-62

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    <span class="mw-page-title-main">Kepler-90h</span> Exoplanet in the constellation Draco

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    <span class="mw-page-title-main">Kepler-442b</span> Super-Earth orbiting Kepler-442

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    <span class="mw-page-title-main">Kepler-452b</span> Super-Earth exoplanet orbiting Kepler-452

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    <span class="mw-page-title-main">Kepler-1229b</span> Super-Earth orbiting Kepler-1229

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    <span class="mw-page-title-main">K2-288Bb</span> Mini-Neptune orbiting K2-288B

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