54 Piscium
Encyclopedia
54 Piscium is an orange dwarf
star
approximately 36 light-year
s away in the constellation
of Pisces
. In 2002, an extrasolar planet
was confirmed to be orbiting the star, and in 2006, a brown dwarf
was also discovered orbiting it.
54 Piscium is an orange dwarf
star
of the spectral type K0V. It has been calculated that the star may have 79 percent of the Sun
's mass
and 46 percent of the luminosity
. The radius
has been directly determined by interferometry
to be 94 percent that of the sun using the CHARA array
. The rotational period of 54 Piscium is about 48 days. It is though that the star is about 5.1 billion years old (based on chromospheric activity and isochronal analysis). The star appears to be about 1.1 times more enriched with elements heavier than hydrogen
(based on its abundance of iron
).
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In 2006, a direct image of 54 Piscium showed that there was a brown dwarf
companion to 54 Piscium A. 54 Piscium B is though to be a "methane brown dwarf" of the spectral type "T7.5V". A comparison of its luminosity suggests that the substellar object has a mass of 0.051 that of the Sun
(50 times the mass
of Jupiter
), along. Similar to Gliese 570 D, this brown dwarf is though to have a surface temperature between 500 and 600 degrees Celsius.
When 54 Piscium B was directly imaged by NASA
's Spitzer Space Telescope
, it was shown that the brown dwarf had a projected separation of around 476 astronomical unit
s from the primary star. 54 Piscium B was the first brown dwarf to be detected around a star with an already known extrasolar planet
(based on radial velocity
surveys).
(named 54 Piscium b
) around 54 Piscium. The planet has been estimated to have a mass
of only 20 percent that of Jupiter
(making the planet around the same size and mass of Saturn
).
The planet orbits its sun at a distance of 0.28 astronomical unit
s (which would be within the orbit of Mercury
), which takes approximately 62 day
s to complete. The planet has a high eccentricity
of about 0.63. The highly elliptical orbit, however, suggested that the gravity of an unseen object farther away from the star was pulling the planet outward. The eccentric orbit became clear with the discovery of the brown dwarf
within the system.
The orbit of an Earth
-like planet would need to be centered within 0.68 AU (around the orbital distance of Venus), which in a Keplerian system means a 240 day orbital period. In a later simulation with the brown dwarf, 54 Piscium b's orbit "sweeps clean" most test particles within 0.5 AU, leaving only asteroids "in low-eccentricity orbits near the known planet’s apastron distance, near the 1:2 mean-motion resonance". Also, observation has ruled out Neptune-class or heavier planets with a period of one year or less; which still allows for Earth-sized planets at 0.6 AU or more.
Orange dwarf
A K-type main-sequence star , also referred to orange dwarf, are main-sequence stars of spectral type K and luminosity class V. These stars are intermediate in size between red M-type main-sequence stars and yellow G-type main-sequence stars...
star
Star
A star is a massive, luminous sphere of plasma held together by gravity. At the end of its lifetime, a star can also contain a proportion of degenerate matter. The nearest star to Earth is the Sun, which is the source of most of the energy on Earth...
approximately 36 light-year
Light-year
A light-year, also light year or lightyear is a unit of length, equal to just under 10 trillion kilometres...
s away in the constellation
Constellation
In modern astronomy, a constellation is an internationally defined area of the celestial sphere. These areas are grouped around asterisms, patterns formed by prominent stars within apparent proximity to one another on Earth's night sky....
of Pisces
Pisces (constellation)
Pisces is a constellation of the zodiac. Its name is the Latin plural for fish, and its symbol is . It lies between Aquarius to the west and Aries to the east...
. In 2002, an extrasolar planet
Extrasolar planet
An extrasolar planet, or exoplanet, is a planet outside the Solar System. A total of such planets have been identified as of . It is now known that a substantial fraction of stars have planets, including perhaps half of all Sun-like stars...
was confirmed to be orbiting the star, and in 2006, a brown dwarf
Brown dwarf
Brown dwarfs are sub-stellar objects which are too low in mass to sustain hydrogen-1 fusion reactions in their cores, which is characteristic of stars on the main sequence. Brown dwarfs have fully convective surfaces and interiors, with no chemical differentiation by depth...
was also discovered orbiting it.
Stellar components
Orange dwarf
A K-type main-sequence star , also referred to orange dwarf, are main-sequence stars of spectral type K and luminosity class V. These stars are intermediate in size between red M-type main-sequence stars and yellow G-type main-sequence stars...
star
Star
A star is a massive, luminous sphere of plasma held together by gravity. At the end of its lifetime, a star can also contain a proportion of degenerate matter. The nearest star to Earth is the Sun, which is the source of most of the energy on Earth...
of the spectral type K0V. It has been calculated that the star may have 79 percent of the Sun
Sun
The Sun is the star at the center of the Solar System. It is almost perfectly spherical and consists of hot plasma interwoven with magnetic fields...
's mass
Mass
Mass can be defined as a quantitive measure of the resistance an object has to change in its velocity.In physics, mass commonly refers to any of the following three properties of matter, which have been shown experimentally to be equivalent:...
and 46 percent of the luminosity
Luminosity
Luminosity is a measurement of brightness.-In photometry and color imaging:In photometry, luminosity is sometimes incorrectly used to refer to luminance, which is the density of luminous intensity in a given direction. The SI unit for luminance is candela per square metre.The luminosity function...
. The radius
Radius
In classical geometry, a radius of a circle or sphere is any line segment from its center to its perimeter. By extension, the radius of a circle or sphere is the length of any such segment, which is half the diameter. If the object does not have an obvious center, the term may refer to its...
has been directly determined by interferometry
Interferometry
Interferometry refers to a family of techniques in which electromagnetic waves are superimposed in order to extract information about the waves. An instrument used to interfere waves is called an interferometer. Interferometry is an important investigative technique in the fields of astronomy,...
to be 94 percent that of the sun using the CHARA array
CHARA array
The CHARA Array is an optical astronomical interferometer operated by The Center for High Angular Resolution Astronomy of the Georgia State University . CHARA is the World's highest angular resolution telescope at near-infrared wavelengths...
. The rotational period of 54 Piscium is about 48 days. It is though that the star is about 5.1 billion years old (based on chromospheric activity and isochronal analysis). The star appears to be about 1.1 times more enriched with elements heavier than 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...
(based on its abundance of iron
Iron
Iron is a chemical element with the symbol Fe and atomic number 26. It is a metal in the first transition series. It is the most common element forming the planet Earth as a whole, forming much of Earth's outer and inner core. It is the fourth most common element in the Earth's crust...
).
Brown dwarf
Brown dwarfs are sub-stellar objects which are too low in mass to sustain hydrogen-1 fusion reactions in their cores, which is characteristic of stars on the main sequence. Brown dwarfs have fully convective surfaces and interiors, with no chemical differentiation by depth...
companion to 54 Piscium A. 54 Piscium B is though to be a "methane brown dwarf" of the spectral type "T7.5V". A comparison of its luminosity suggests that the substellar object has a mass of 0.051 that of the Sun
Sun
The Sun is the star at the center of the Solar System. It is almost perfectly spherical and consists of hot plasma interwoven with magnetic fields...
(50 times the mass
Mass
Mass can be defined as a quantitive measure of the resistance an object has to change in its velocity.In physics, mass commonly refers to any of the following three properties of matter, which have been shown experimentally to be equivalent:...
of 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,...
), along. Similar to Gliese 570 D, this brown dwarf is though to have a surface temperature between 500 and 600 degrees Celsius.
When 54 Piscium B was directly imaged by 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...
's Spitzer Space Telescope
Spitzer Space Telescope
The Spitzer Space Telescope , formerly the Space Infrared Telescope Facility is an infrared space observatory launched in 2003...
, it was shown that the brown dwarf had a projected separation of around 476 astronomical unit
Astronomical unit
An astronomical unit is a unit of length equal to about or approximately the mean Earth–Sun distance....
s from the primary star. 54 Piscium B was the first brown dwarf to be detected around a star with an already known extrasolar planet
Extrasolar planet
An extrasolar planet, or exoplanet, is a planet outside the Solar System. A total of such planets have been identified as of . It is now known that a substantial fraction of stars have planets, including perhaps half of all Sun-like stars...
(based on radial velocity
Radial velocity
Radial velocity is the velocity of an object in the direction of the line of sight . In astronomy, radial velocity most commonly refers to the spectroscopic radial velocity...
surveys).
Planetary system
On January 16, 2002, a team of astronomers (led by Geoff Marcy) announced the discovery of an extrasolar planetExtrasolar planet
An extrasolar planet, or exoplanet, is a planet outside the Solar System. A total of such planets have been identified as of . It is now known that a substantial fraction of stars have planets, including perhaps half of all Sun-like stars...
(named 54 Piscium b
54 Piscium b
54 Piscium b , occasionally catalogued as 54 Piscium Ab in order to differentiate from the brown dwarf in the system, is an extrasolar planet approximately 36 light-years away in the constellation of Pisces. The planet was discovered orbiting the orange dwarf star 54 Piscium...
) around 54 Piscium. The planet has been estimated to have a mass
Mass
Mass can be defined as a quantitive measure of the resistance an object has to change in its velocity.In physics, mass commonly refers to any of the following three properties of matter, which have been shown experimentally to be equivalent:...
of only 20 percent that of 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,...
(making the planet around the same size and mass of 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,...
).
The planet orbits its sun at a distance of 0.28 astronomical unit
Astronomical unit
An astronomical unit is a unit of length equal to about or approximately the mean Earth–Sun distance....
s (which would be within the orbit of Mercury
Mercury (planet)
Mercury is the innermost and smallest planet in the Solar System, orbiting the Sun once every 87.969 Earth days. The orbit of Mercury has the highest eccentricity of all the Solar System planets, and it has the smallest axial tilt. It completes three rotations about its axis for every two orbits...
), which takes approximately 62 day
Day
A day is a unit of time, commonly defined as an interval equal to 24 hours. It also can mean that portion of the full day during which a location is illuminated by the light of the sun...
s to complete. The planet has a high eccentricity
Orbital eccentricity
The orbital eccentricity of an astronomical body is the amount by which its orbit deviates from a perfect circle, where 0 is perfectly circular, and 1.0 is a parabola, and no longer a closed orbit...
of about 0.63. The highly elliptical orbit, however, suggested that the gravity of an unseen object farther away from the star was pulling the planet outward. The eccentric orbit became clear with the discovery of the brown dwarf
Brown dwarf
Brown dwarfs are sub-stellar objects which are too low in mass to sustain hydrogen-1 fusion reactions in their cores, which is characteristic of stars on the main sequence. Brown dwarfs have fully convective surfaces and interiors, with no chemical differentiation by depth...
within the system.
The orbit of an Earth
Earth
Earth is the third planet from the Sun, and the densest and fifth-largest of the eight planets in the Solar System. It is also the largest of the Solar System's four terrestrial planets...
-like planet would need to be centered within 0.68 AU (around the orbital distance of Venus), which in a Keplerian system means a 240 day orbital period. In a later simulation with the brown dwarf, 54 Piscium b's orbit "sweeps clean" most test particles within 0.5 AU, leaving only asteroids "in low-eccentricity orbits near the known planet’s apastron distance, near the 1:2 mean-motion resonance". Also, observation has ruled out Neptune-class or heavier planets with a period of one year or less; which still allows for Earth-sized planets at 0.6 AU or more.