Kepler-444 (or KOI-3158, KIC 6278762, 2MASS J19190052+4138043, BD+41°3306)
is a
triple star system
A star system or stellar system is a small number of stars that orbit each other, bound by gravitational attraction. A large group of stars bound by gravitation is generally called a ''star cluster'' or ''galaxy'', although, broadly speaking, ...
, estimated to be 11.2 billion years old (more than 80% of the age of the
universe
The universe is all of space and time and their contents, including planets, stars, galaxies, and all other forms of matter and energy. The Big Bang theory is the prevailing cosmological description of the development of the universe. Acc ...
),
approximately away from
Earth
Earth is the third planet from the Sun and the only astronomical object known to harbor life. While large volumes of water can be found throughout the Solar System, only Earth sustains liquid surface water. About 71% of Earth's surfa ...
in the
constellation
A constellation is an area on the celestial sphere in which a group of visible stars forms Asterism (astronomy), a perceived pattern or outline, typically representing an animal, mythological subject, or inanimate object.
The origins of the e ...
Lyra
Lyra (; Latin for lyre, from Greek ''λύρα'') is a small constellation. It is one of the 48 listed by the 2nd century astronomer Ptolemy, and is one of the modern 88 constellations recognized by the International Astronomical Union. Lyra was ...
. On 27 January 2015, the
''Kepler'' spacecraft is reported to have confirmed the detection of five sub-Earth-sized
rocky
''Rocky'' is a 1976 American sports drama film directed by John G. Avildsen and written by and starring Sylvester Stallone. It is the first installment in the ''Rocky'' franchise and stars Talia Shire, Burt Young, Carl Weathers, and Burgess M ...
exoplanets
An exoplanet or extrasolar planet is a planet outside the Solar System. The first possible evidence of an exoplanet was noted in 1917 but was not recognized as such. The first confirmation of detection occurred in 1992. A different planet, init ...
orbiting the main star. The star is a
K-type main sequence star
A K-type main-sequence star, also referred to as a K-type dwarf or an orange dwarf, is a main-sequence (hydrogen-burning) star of spectral type K and luminosity class V. These stars are intermediate in size between red M-type main-sequence stars ...
.
All of the planets are far too close to their star to harbour life forms.
Discovery
Preliminary results of the planetary system around Kepler-444 were first announced at the second
Kepler Science Conference in 2013. At that conference, the star was known as KOI-3158.
Characteristics
The star, Kepler-444, is approximately 11.2 billion years old, whereas the
Sun
The Sun is the star at the center of the Solar System. It is a nearly perfect ball of hot plasma, heated to incandescence by nuclear fusion reactions in its core. The Sun radiates this energy mainly as light, ultraviolet, and infrared radi ...
is only 4.6 billion years old. The age is that of Kepler-444 A, an
orange main sequence star of spectral type K0.
The original research on Kepler-444 was published in ''
The Astrophysical Journal
''The Astrophysical Journal'', often abbreviated ''ApJ'' (pronounced "ap jay") in references and speech, is a peer-reviewed
Peer review is the evaluation of work by one or more people with similar competencies as the producers of the work ...
'' on 27 January 2015 under the title "An ancient extrasolar system with five sub-Earth-size planets" by a team of 40 authors, the abstract reads as follows:
The chemical composition of stars hosting small exoplanets (with radii less than four Earth radii) appears to be more diverse than that of gas-giant hosts, which tend to be metal-rich
In astronomy, metallicity is the abundance of elements present in an object that are heavier than hydrogen and helium. Most of the normal physical matter in the Universe is either hydrogen or helium, and astronomers use the word ''"metals"'' as a ...
. This implies that small, including Earth-size, planets may have readily formed at earlier epochs in the Universe's history when metals were more scarce. We report Kepler spacecraft observations of Kepler-444, a metal-poor Sun-like star from the old population of the Galactic thick disk and the host to a compact system of five transiting planets with sizes between those of Mercury and Venus. We validate this system as a true five-planet system orbiting the target star and provide a detailed characterization of its planetary and orbital parameters based on an analysis of the transit photometry
Any planet is an extremely faint light source compared to its parent star. For example, a star like the Sun is about a billion times as bright as the reflected light from any of the planets orbiting it. In addition to the intrinsic difficulty ...
. Kepler-444 is the densest star with detected solar-like oscillations. We use asteroseismology
Asteroseismology or astroseismology is the study of oscillations in stars. Stars have many resonant modes and frequencies, and the path of sound waves passing through a star depends on the speed of sound, which in turn depends on local temperature ...
to directly measure a precise age of 11.2+/-1.0 Gyr for the host star, indicating that Kepler-444 formed when the Universe was less than 20% of its current age and making it the oldest known system of terrestrial-size planets. We thus show that Earth-size planets have formed throughout most of the Universe's 13.8-billion-year history, leaving open the possibility for the existence of ancient life in the Galaxy
A galaxy is a system of stars, stellar remnants, interstellar gas, dust, dark matter, bound together by gravity. The word is derived from the Greek ' (), literally 'milky', a reference to the Milky Way galaxy that contains the Solar System. ...
. The age of Kepler-444 not only suggests that thick-disk stars were among the hosts to the first Galactic planets, but may also help to pinpoint the beginning of the era of planet formation
The nebular hypothesis is the most widely accepted model in the field of cosmogony to explain the formation and evolution of the Solar System (as well as other planetary systems). It suggests the Solar System is formed from gas and dust orbitin ...
." The star is believed to have 2 M dwarfs in orbit around it with the fainter companion 1.8 arc-seconds from the main star.
Stellar system
The Kepler-444 system consists of the planet hosting primary and a pair of M-dwarf stars. The M-dwarfs orbit each other at a distance of less than 0.3
AU while the pair orbits the primary in a highly
eccentric
Eccentricity or eccentric may refer to:
* Eccentricity (behavior), odd behavior on the part of a person, as opposed to being "normal"
Mathematics, science and technology Mathematics
* Off-center, in geometry
* Eccentricity (graph theory) of a v ...
200-year orbit. The pair comes within 5 AU of the primary potentially severely truncating the protoplanetary disk from which the planets formed at 1–2 AU. This would have depleted the availability of solid material to form the observed planets.
Planetary system
All five rocky exoplanets (Kepler-444b; Kepler-444c; Kepler-444d; Kepler-444e; Kepler-444f) are confirmed,
smaller than the size of
Venus
Venus is the second planet from the Sun. It is sometimes called Earth's "sister" or "twin" planet as it is almost as large and has a similar composition. As an interior planet to Earth, Venus (like Mercury) appears in Earth's sky never fa ...
(but bigger than
Mercury
Mercury commonly refers to:
* Mercury (planet), the nearest planet to the Sun
* Mercury (element), a metallic chemical element with the symbol Hg
* Mercury (mythology), a Roman god
Mercury or The Mercury may also refer to:
Companies
* Merc ...
) and each of the exoplanets completes an orbit around the host star in less than 10 days.
Thus, the planetary system is very compact, as even the furthest planet, Kepler-444f, still orbits closer to the star than Mercury is to the
Sun
The Sun is the star at the center of the Solar System. It is a nearly perfect ball of hot plasma, heated to incandescence by nuclear fusion reactions in its core. The Sun radiates this energy mainly as light, ultraviolet, and infrared radi ...
.
According to NASA, no life as we know it could exist on these hot exoplanets, due to their close orbital distances to the host star.
To keep the known planetary system stable, no additional giant planets can be located within 5.5
AU of the parent star.
See also
*
Kepler-80
Kepler-80, also known as KOI-500, is a red dwarf star of the spectral type M0V. This stellar classification places Kepler-80 among the very common, cool, class M stars that are still within their main evolutionary stage, known as the main ...
- most compact 5-planet system discovered so far
*
List of extrasolar planets
These are lists of exoplanets. Most of these were discovered by the Kepler space telescope. There are an additional 2,054 potential exoplanets from Kepler's first mission yet to be confirmed, as well as 978 from its " Second Light" mission and ...
*
PSR B1620-26
PSR may refer to:
Organizations
* Pacific School of Religion, Berkeley, California, US
* Palestinian Center for Policy and Survey Research
* Physicians for Social Responsibility, US
;Political parties:
* Revolutionary Socialist Party (Portugal) ( ...
- an ancient planetary system in
Messier 4
Messier 4 or M4 (also designated NGC 6121) is a globular cluster in the constellation of Scorpius. It was discovered by Philippe Loys de Chéseaux in 1745 and catalogued by Charles Messier in 1764. It was the first globular cluster in which indiv ...
References
External links
NASA – Kepler-444/KOI-3158at
The NASA Exoplanet Archive
NASA – Kepler-444bcdef
at Extrasolar Planets Encyclopaedia
The Extrasolar Planets Encyclopaedia is an astronomy website, founded in Paris, France at the Meudon Observatory by Jean Schneider in February 1995, which maintains a database of all the currently known and candidate extrasolar planets, with indi ...
{{Sky, 19, 19, 01.0, +, 41, 38, 05, 117
Lyra (constellation)
Planetary systems with five confirmed planets
K-type main-sequence stars
3158
Planetary transit variables
J19190052+4138043
94931
Durchmusterung objects
M-type main-sequence stars
Triple star systems
TIC objects