Rho Coronae Borealis
Encyclopedia
Rho Coronae Borealis (ρ CrB, ρ Coronae Borealis) is a Solar twin, yellow dwarf
star
approximately 57 light-year
s away in the constellation
of Corona Borealis
. The star is thought to be similar to the Sun
with nearly the same mass
, radius
, and luminosity
. As of 1997, an extrasolar planet
has been confirmed to be orbiting the star. It is thought that the star may have a stellar companion, but it may be just an optical
companion.
star of the spectral type "G0-2Va". The star is thought to have only 95 percent of the Sun's mass, along with 1.31 times its radius and 1.61 of its luminosity. It may only be 51 to 65 percent as enriched with elements heavier than hydrogen
(based on its abundance of iron
) and may be somewhat older than the Sun at around six billion years old.
In 2000, preliminary Hipparcos
astrometrical satellite
data indicated that the orbital inclination of the star's companion was 0.5°, implying that its mass was as much as 115 times Jupiter's. Such a massive body would have to be a dim red dwarf
, not a planet. However, this scenario is statistically
very improbable, and the claim has not been independently verified.
. The planet's distance to the star is only about one fifth Earth's
distance from the Sun. The orbit is circular and it takes 40 days to complete one revolution around the star. The planet has a mass about that of Jupiter
. However, the inclination
of the orbital plane
is not known, so the stated value represents a minimum. If the planet orbits in the same plane as the circumstellar disk, the inclination would be about 46°, implying a planetary mass of 1.5 times Jupiter.
announced the existence of a circumstellar disk
that may be similar in composition to the Kuiper Belt
of the Solar system
. The disk may extend out to 85 astronomical unit
s out from Rho Coronae Borealis (which is beyond the orbital distances of Neptune
and Pluto
from the Sun). It is inclined at about 46° from Earth's line of sight. However observations with the Spitzer Space Telescope
failed to detect any infrared excess at 24 or 70 micrometres wavelengths, which would be expected if a disk were present.
Yellow dwarf
A G-type main-sequence star , often called a yellow dwarf, is a main-sequence star of spectral type G and luminosity class V. Such a star has about 0.8 to 1.2 solar masses and surface temperature of between 5,300 and 6,000 K., Tables VII, VIII...
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 57 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 Corona Borealis
Corona Borealis
Corona Borealis is a small constellation in the northern sky. Its name is Latin for "northern crown", a name inspired by its shape; its main stars form a semicircular arc. It was one of the 48 constellations listed by the 2nd century astronomer Ptolemy and remains one of the 88 modern...
. The star is thought to be similar to 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...
with nearly the same 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:...
, 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...
, and 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...
. As of 1997, 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...
has been confirmed to be orbiting the star. It is thought that the star may have a stellar companion, but it may be just an optical
Double star
In observational astronomy, a double star is a pair of stars that appear close to each other in the sky as seen from Earth when viewed through an optical telescope. This can happen either because the pair forms a binary star, i.e...
companion.
Stellar components
Rho Coronae Borealis is a Solar twin, yellow dwarfYellow dwarf
A G-type main-sequence star , often called a yellow dwarf, is a main-sequence star of spectral type G and luminosity class V. Such a star has about 0.8 to 1.2 solar masses and surface temperature of between 5,300 and 6,000 K., Tables VII, VIII...
star of the spectral type "G0-2Va". The star is thought to have only 95 percent of the Sun's mass, along with 1.31 times its radius and 1.61 of its luminosity. It may only be 51 to 65 percent as 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...
) and may be somewhat older than the Sun at around six billion years old.
In 2000, preliminary Hipparcos
Hipparcos
Hipparcos was a scientific mission of the European Space Agency , launched in 1989 and operated between 1989 and 1993. It was the first space experiment devoted to precision astrometry, the accurate measurement of the positions of celestial objects on the sky...
astrometrical satellite
Satellite
In the context of spaceflight, a satellite is an object which has been placed into orbit by human endeavour. Such objects are sometimes called artificial satellites to distinguish them from natural satellites such as the Moon....
data indicated that the orbital inclination of the star's companion was 0.5°, implying that its mass was as much as 115 times Jupiter's. Such a massive body would have to be a dim red dwarf
Red dwarf
According to the Hertzsprung-Russell diagram, a red dwarf star is a small and relatively cool star, of the main sequence, either late K or M spectral type....
, not a planet. However, this scenario is statistically
Statistics
Statistics is the study of the collection, organization, analysis, and interpretation of data. It deals with all aspects of this, including the planning of data collection in terms of the design of surveys and experiments....
very improbable, and the claim has not been independently verified.
Planetary system
Planet
The planet, one of the first discovered (on April 24, 1997) is designated as Rho Coronae Borealis bRho Coronae Borealis b
Rho Coronae Borealis b is an extrasolar planet approximately 57 light-years away in the constellation of Corona Borealis. The planet was discovered orbiting the Solar twin, yellow dwarf star Rho Coronae Borealis in April 1997 . The planet's distance to the star is only about one fifth Earth's...
. The planet's distance to the star is only about one fifth Earth's
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...
distance from the Sun. The orbit is circular and it takes 40 days to complete one revolution around the star. The planet has a mass about 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,...
. However, the inclination
Inclination
Inclination in general is the angle between a reference plane and another plane or axis of direction.-Orbits:The inclination is one of the six orbital parameters describing the shape and orientation of a celestial orbit...
of the orbital plane
Orbital plane (astronomy)
All of the planets, comets, and asteroids in the solar system are in orbit around the Sun. All of those orbits line up with each other making a semi-flat disk called the orbital plane. The orbital plane of an object orbiting another is the geometrical plane in which the orbit is embedded...
is not known, so the stated value represents a minimum. If the planet orbits in the same plane as the circumstellar disk, the inclination would be about 46°, implying a planetary mass of 1.5 times Jupiter.
Unconfirmed circumstellar disk
In October 1999, astronomers at the University of ArizonaUniversity of Arizona
The University of Arizona is a land-grant and space-grant public institution of higher education and research located in Tucson, Arizona, United States. The University of Arizona was the first university in the state of Arizona, founded in 1885...
announced the existence of a circumstellar disk
Circumstellar disk
A circumstellar disk is a torus, pancake or ring-shaped accumulation of matter composed of gas, dust, planetesimals, asteroids or collision fragments in orbit around a star. Around the youngest stars, they are the reservoirs of material out of which planets may form...
that may be similar in composition to the Kuiper Belt
Kuiper belt
The Kuiper belt , sometimes called the Edgeworth–Kuiper belt, is a region of the Solar System beyond the planets extending from the orbit of Neptune to approximately 50 AU from the Sun. It is similar to the asteroid belt, although it is far larger—20 times as wide and 20 to 200 times as massive...
of the Solar system
Solar System
The Solar System consists of the Sun and the astronomical objects gravitationally bound in orbit around it, all of which formed from the collapse of a giant molecular cloud approximately 4.6 billion years ago. The vast majority of the system's mass is in the Sun...
. The disk may extend out to 85 astronomical unit
Astronomical unit
An astronomical unit is a unit of length equal to about or approximately the mean Earth–Sun distance....
s out from Rho Coronae Borealis (which is beyond the orbital distances of Neptune
Neptune
Neptune is the eighth and farthest planet from the Sun in the Solar System. Named for the Roman god of the sea, it is the fourth-largest planet by diameter and the third largest by mass. Neptune is 17 times the mass of Earth and is slightly more massive than its near-twin Uranus, which is 15 times...
and Pluto
Pluto
Pluto, formal designation 134340 Pluto, is the second-most-massive known dwarf planet in the Solar System and the tenth-most-massive body observed directly orbiting the Sun...
from the Sun). It is inclined at about 46° from Earth's line of sight. However observations with the Spitzer Space Telescope
Spitzer Space Telescope
The Spitzer Space Telescope , formerly the Space Infrared Telescope Facility is an infrared space observatory launched in 2003...
failed to detect any infrared excess at 24 or 70 micrometres wavelengths, which would be expected if a disk were present.