55 Cancri (abbreviated 55 Cnc; Bayer designation ρ¹ Cancri, Rho-1 Cancri) is a nearby 6th magnitude star in the constellation Cancer. The star is a binary system. The primary component is, like our Sun, a yellow dwarf, but slightly less massive and luminous. Secondary is a distant dim red dwarf. Distance to the system is 41 light years. The brighter component is visible through binoculars or to the naked eye under very dark skies. In astronomy, an epoch is a moment in time for which celestial coordinates or orbital elements are specified. ... This article is about the year 2000. ... Orion is a remarkable constellation, visible from most places on the globe (but not always the whole year long). ... In astronomy and astrology, Cancer ( ), Latin for crab, is one of the twelve constellations of the zodiac. ... Right ascension (RA; symbol α: Greek letter alpha) is the astronomical term for one of the two coordinates of a point on the celestial sphere when using the equatorial coordinate system. ... In astronomy, declination (dec) is one of the two coordinates of the equatorial coordinate system, the other being either right ascension or hour angle. ... A light year, abbreviated ly, is the distance light travels in one year: roughly 9. ... The parsec (symbol pc) is a unit of length used in astronomy. ... In astronomy, stellar classification is a classification of stars based initially on photospheric temperature and its associated spectral characteristics, and subsequenly refined in terms of other characteristics. ... The apparent magnitude (m) of a star, planet or other heavenly body is a measure of its apparent brightness; that is, the amount of light received from the object. ... Many of the brighter stars are given names which are known as Bayer designations. ... The apparent magnitude (m) of a star, planet or other heavenly body is a measure of its apparent brightness; that is, the amount of light received from the object. ... The Pleiades star cluster A star is a massive body of plasma in outer space that is currently producing or has produced energy through nuclear fusion. ... Orion is a remarkable constellation, visible from most places on the globe (but not always the whole year long). ... In astronomy and astrology, Cancer ( ), Latin for crab, is one of the twelve constellations of the zodiac. ... A binary star system consists of two stars both orbiting around their barycenter. ... The Sun is the star at the centre of our Solar system. ... Large solar flare recorded by SOHO EIT304 instrument in the ultraviolet. ... Red Dwarf is a British science fiction comedy, created and originally written by Rob Grant and Doug Naylor. ... A light year, abbreviated ly, is the distance light travels in one year: roughly 9. ... Binoculars A set or pair of binoculars (the word is usually used in the plural) is a contraction of the more accurate name binocular telescope, and comprises two telescopes mounted side-by-side and aligned to point accurately in the same direction, one for each of the users eyes. ...

Four extrasolar planets have been discovered around 55 Cancri A, making it the largest known extrasolar planetary system as of 2004. Its planets orbit with periods of 3, 15, 44 and 4,520 days. The smallest planet, which orbits the star in just under three days, is about the same size as Neptune, making it one of the smallest extrasolar planets ever discovered. This is the first and so far only known four planet planetary system. Infrared image of the star GQ Lupi (A) orbited by a planet (b) at a distance of approximately 20 times the distance between Jupiter and our Sun. ... 2004 is a leap year starting on Thursday of the Gregorian calendar. ... A planet in common parlance is a large object in orbit around a star that is not a star itself. ... Atmospheric characteristics Surface pressure ≫100 MPa Hydrogen - H2 80% ±3. ...

The planets

Traditionally, extrasolar planets are named using their primary star's name plus a lowercase letter in order of the planet's discovery from the star, starting with "b" rather than "a" (b, c, d, e, f, ...). So, for example, the third planet discovered around 55 Cancri is called "55 Cancri d". Capital letters (A, B, C, D) are used for stellar companions; this leads to a situation here where 55 Cancri's distant red dwarf companion is called 55 Cancri B, but the star's first discovered planet is called 55 Cancri b. Sometimes, to prevent confusion, the planet is called 55 Cancri Ab, refering to its primary as 55 Cancri A rather than simply 55 Cancri.

So far, four planets have been discovered orbiting the main solar-type star; there are hints that there may be a fifth planet orbiting just exterior to the first three. The red dwarf companion (55 Cancri B) appears at this point to be planet-free.

55 Cancri e

Innermost planet, designated as 55 Cancri e is one of three currently known "hot Neptunes" or "super-Earths" with a mass only 14 Earth masses. Like Neptune, it is a small gas giant – or perhaps more likely – a very large terrestrial planet with dense atmosphere. Distance to the star is less than 1/26th Earth's distance from the Sun; the planet orbits the star in mere 2.8 days. Despite its closeness, the orbit is somewhat eccentric due to the gravitational perturbation caused by the nearby massive planet b. In geometry, the term semi-major axis (also semimajor axis) is used to describe the dimensions of ellipses and hyperbolas. ... The astronomical unit (AU or au or a. ... In astrodynamics, under standard assumptions any orbit must be of conic section shape. ... The orbital period is the time it takes a planet (or another object) to make one full orbit. ... See also Day (language) A day (symbol: d) is a unit of time. ... Inclination is one of the six orbital parameters describing the shape and orientation of a celestial orbit and is the angular distance of the orbital plane from the plane of the reference (usually planets equator or the ecliptic), stated in degrees. ... Map of Earth showing lines of longitude, which appear curved and vertical in this projection, but are actually halves of great circles Longitude, sometimes denoted by the Greek letter λ, describes the location of a place on Earth east or west of a north-south line called the Prime Meridian. ... elements of an orbit. ... elements of an orbit. ... The Julian day or Julian day number (JDN) is the number of days that have elapsed since 12 noon Greenwich Mean Time (UT or TT) on Monday, January 1, 4713 BC in the proleptic Julian calendar . ... Mass is a property of physical objects that, roughly speaking, measures the amount of matter they contain. ... Atmospheric characteristics Atmospheric pressure 70 kPa Hydrogen ~86% Helium ~14% Methane 0. ... RADIUS (Remote Authentication Dial In User Service) is an AAA (authentication, authorization and accounting) protocol for applications such as network access or IP mobility. ... Density (symbol: ρ - Greek: rho) is a measure of mass per unit of volume. ... The international prototype, made of platinum-iridium, which is kept at the BIPM under conditions specified by the 1st CGPM in 1889. ... The cubic metre (symbol m³) is the SI derived unit of volume. ... Temperature is the physical property of a system which underlies the common notions of hot and cold; the material with the higher temperature is said to be hotter. ... The kelvin (symbol: K) is the SI unit of temperature, and is one of the seven SI base units. ... This article needs to be cleaned up to conform to a higher standard of quality. ... 2004 (MMIV) was a leap year starting on Thursday of the Gregorian calendar. ... Atmospheric characteristics Surface pressure ≫100 MPa Hydrogen - H2 80% ±3. ... Earth, also known as the Earth, Terra, and (mostly in the 19th century) Tellus, is the third-closest planet to the Sun. ... A gas giant is a large planet that is not composed mostly of rock or other solid matter. ... A Earths solar system has four terrestrial planets: Mercury, Venus, Earth and Mars. ... See also Day (language) A day (symbol: d) is a unit of time. ... In astrodynamics, under standard assumptions any orbit must be of conic section shape. ... Gravitation is the tendency of massive objects to accelerate towards each other. ... Perturbation is a term used in astronomy to describe alterations to an objects orbit caused by gravitational interactions with other bodies. ...

The planet was discovered by the Hobby-Eberly Telescope in 2004. The telescope is devoted to spectroscopic studies and has one of the most accurate radial velocity instruments. The Hobby-Eberly Telescope at the McDonald Observatory is primarily used for spectography. ... 2004 (MMIV) was a leap year starting on Thursday of the Gregorian calendar. ... Extremely high resolution spectrum of the Sun showing thousands of elemental absorption lines (fraunhofer lines) Spectroscopy is the study of spectra, that is, the dependence of physical quantities on frequency. ... Radial velocity is the velocity of an object in the direction of the line of sight. ...

In 2005, Jack Wisdom questioned the existence of the planet. According to him, the signal caused by the planet actually comes from 55 Cancri c. Instead of the "hot Neptune", he claims that there is a small, 1.8 Neptune mass (31 Earth mass) gas giant in an orbit with a period of about 261 days. [1] 2005 (MMV) is a common year starting on Saturday of the Gregorian calendar. ... Jack Wisdom is a Professor of Planetary Sciences at the Massachusetts Institute of Technology. ...

55 Cancri b

Discovered in 1996, 55 Cancri b was the fourth extrasolar planet discovered around a normal star. It is slightly less massive than Jupiter and orbits very near the star, completing one revolution around the star in less than 15 days. In geometry, the term semi-major axis (also semimajor axis) is used to describe the dimensions of ellipses and hyperbolas. ... The astronomical unit (AU or au or a. ... In astrodynamics, under standard assumptions any orbit must be of conic section shape. ... The orbital period is the time it takes a planet (or another object) to make one full orbit. ... See also Day (language) A day (symbol: d) is a unit of time. ... Inclination is one of the six orbital parameters describing the shape and orientation of a celestial orbit and is the angular distance of the orbital plane from the plane of the reference (usually planets equator or the ecliptic), stated in degrees. ... Map of Earth showing lines of longitude, which appear curved and vertical in this projection, but are actually halves of great circles Longitude, sometimes denoted by the Greek letter λ, describes the location of a place on Earth east or west of a north-south line called the Prime Meridian. ... elements of an orbit. ... elements of an orbit. ... The Julian day or Julian day number (JDN) is the number of days that have elapsed since 12 noon Greenwich Mean Time (UT or TT) on Monday, January 1, 4713 BC in the proleptic Julian calendar . ... Mass is a property of physical objects that, roughly speaking, measures the amount of matter they contain. ... Atmospheric characteristics Atmospheric pressure 70 kPa Hydrogen ~86% Helium ~14% Methane 0. ... RADIUS (Remote Authentication Dial In User Service) is an AAA (authentication, authorization and accounting) protocol for applications such as network access or IP mobility. ... Density (symbol: ρ - Greek: rho) is a measure of mass per unit of volume. ... The international prototype, made of platinum-iridium, which is kept at the BIPM under conditions specified by the 1st CGPM in 1889. ... The cubic metre (symbol m³) is the SI derived unit of volume. ... Temperature is the physical property of a system which underlies the common notions of hot and cold; the material with the higher temperature is said to be hotter. ... The kelvin (symbol: K) is the SI unit of temperature, and is one of the seven SI base units. ... Categories: Astronomers stubs | Astronomers ... Geoffrey Marcy atop the Astronomy Building at UC Berkeley. ... 1996 (MCMXCVI) is a leap year starting on Monday of the Gregorian calendar, and was designated the International Year for the Eradication of Poverty. ... 1996 (MCMXCVI) is a leap year starting on Monday of the Gregorian calendar, and was designated the International Year for the Eradication of Poverty. ... Atmospheric characteristics Atmospheric pressure 70 kPa Hydrogen ~86% Helium ~14% Methane 0. ...

55 Cancri c

55 Cancri c is a small gas giant, having mass about quarter the mass of Jupiter. Having very eccentric orbit, the planet is at apoapsis twice as distant from the star as at periapsis. This would produce extreme seasons on its atmosphere. In geometry, the term semi-major axis (also semimajor axis) is used to describe the dimensions of ellipses and hyperbolas. ... The astronomical unit (AU or au or a. ... In astrodynamics, under standard assumptions any orbit must be of conic section shape. ... The orbital period is the time it takes a planet (or another object) to make one full orbit. ... See also Day (language) A day (symbol: d) is a unit of time. ... Inclination is one of the six orbital parameters describing the shape and orientation of a celestial orbit and is the angular distance of the orbital plane from the plane of the reference (usually planets equator or the ecliptic), stated in degrees. ... Map of Earth showing lines of longitude, which appear curved and vertical in this projection, but are actually halves of great circles Longitude, sometimes denoted by the Greek letter λ, describes the location of a place on Earth east or west of a north-south line called the Prime Meridian. ... elements of an orbit. ... elements of an orbit. ... The Julian day or Julian day number (JDN) is the number of days that have elapsed since 12 noon Greenwich Mean Time (UT or TT) on Monday, January 1, 4713 BC in the proleptic Julian calendar . ... Mass is a property of physical objects that, roughly speaking, measures the amount of matter they contain. ... Atmospheric characteristics Atmospheric pressure 70 kPa Hydrogen ~86% Helium ~14% Methane 0. ... RADIUS (Remote Authentication Dial In User Service) is an AAA (authentication, authorization and accounting) protocol for applications such as network access or IP mobility. ... Density (symbol: ρ - Greek: rho) is a measure of mass per unit of volume. ... The international prototype, made of platinum-iridium, which is kept at the BIPM under conditions specified by the 1st CGPM in 1889. ... The cubic metre (symbol m³) is the SI derived unit of volume. ... Temperature is the physical property of a system which underlies the common notions of hot and cold; the material with the higher temperature is said to be hotter. ... The kelvin (symbol: K) is the SI unit of temperature, and is one of the seven SI base units. ... Geoffrey Marcy atop the Astronomy Building at UC Berkeley. ... Categories: Astronomers stubs | Astronomers ... Professor Fischer showing off her pgplot prowess with a keplerian fit for υ And. ... 2002 (MMII) is a common year starting on Tuesday of the Gregorian calendar. ... This article is about several astronomical terms (apogee & perigee, aphelion & perihelion, generic equivalents based on apsis, and related but rarer terms. ... This article is about several astronomical terms (apogee & perigee, aphelion & perihelion, generic equivalents based on apsis, and related but rarer terms. ...

Its orbit brings it also very close to planet b, closest distance being only a few million kilometres. However, the planets are very close to 3:1 orbital resonance; if that is the case, they will never be very near each other. Also, the gravity of the star helps keeping the orbits stable. A kilometre (American spelling: kilometer), symbol: km is a unit of length in the metric system equal to 1000 metres (from the Greek words χίλια (khilia) = thousand and μέτρο (metro) = count/measure). ... In celestial mechanics, orbital resonance occurs when two orbiting bodies have periods of revolution that are in a simple integer ratio so that they exert a regular gravitational influence on each other. ...

Despite being third planet from the star, 55 Cancri c is still about one third closer to its star than Mercury is from the Sun. Atmospheric characteristics Atmospheric pressure trace Potassium 31. ...

Of the planets of 55 Cancri, this planet is the least certain. There is a small possibility that the signal interpreted as caused by a planet would be actually from the rotation of the star, estimated to have period between 35 and 42 days.

55 Cancri d

The most distant of known planets orbiting 55 Cancri A, 55 Cancri d orbits at a mean distance of about 5 AU, comparable to Jupiter's distance from the Sun. The orbit is quite eccentric. Despite its mass, about four times Jupiter, it is still one of the best Jupiter analogues. In geometry, the term semi-major axis (also semimajor axis) is used to describe the dimensions of ellipses and hyperbolas. ... The astronomical unit (AU or au or a. ... In astrodynamics, under standard assumptions any orbit must be of conic section shape. ... The orbital period is the time it takes a planet (or another object) to make one full orbit. ... A year is the time between two recurrences of an event related to the orbit of the Earth around the Sun. ... See also Day (language) A day (symbol: d) is a unit of time. ... Inclination is one of the six orbital parameters describing the shape and orientation of a celestial orbit and is the angular distance of the orbital plane from the plane of the reference (usually planets equator or the ecliptic), stated in degrees. ... Map of Earth showing lines of longitude, which appear curved and vertical in this projection, but are actually halves of great circles Longitude, sometimes denoted by the Greek letter λ, describes the location of a place on Earth east or west of a north-south line called the Prime Meridian. ... elements of an orbit. ... elements of an orbit. ... The Julian day or Julian day number (JDN) is the number of days that have elapsed since 12 noon Greenwich Mean Time (UT or TT) on Monday, January 1, 4713 BC in the proleptic Julian calendar . ... Mass is a property of physical objects that, roughly speaking, measures the amount of matter they contain. ... Atmospheric characteristics Atmospheric pressure 70 kPa Hydrogen ~86% Helium ~14% Methane 0. ... RADIUS (Remote Authentication Dial In User Service) is an AAA (authentication, authorization and accounting) protocol for applications such as network access or IP mobility. ... Density (symbol: ρ - Greek: rho) is a measure of mass per unit of volume. ... The international prototype, made of platinum-iridium, which is kept at the BIPM under conditions specified by the 1st CGPM in 1889. ... The cubic metre (symbol m³) is the SI derived unit of volume. ... Temperature is the physical property of a system which underlies the common notions of hot and cold; the material with the higher temperature is said to be hotter. ... The kelvin (symbol: K) is the SI unit of temperature, and is one of the seven SI base units. ... Geoffrey Marcy atop the Astronomy Building at UC Berkeley. ... Categories: Astronomers stubs | Astronomers ... Professor Fischer showing off her pgplot prowess with a keplerian fit for υ And. ... 2002 (MMII) is a common year starting on Tuesday of the Gregorian calendar. ... The astronomical unit (AU or au or a. ...

Astrometric measurements with the Fine Guidance Sensors aboard the Hubble Space Telescope have tentatively detected the planet d. According to the measurements, inclination of the planet – and the whole system – is about 53°. If so, true masses of the planets would be about 25% higher than measured with the radial velocity method – firmly placing the planet candidates into the realm of true planethood. Astrometry is a part of astronomy and deals with the positions of stars and other celestial bodies, their distances and movements. ... The Hubble Space Telescope is a telescope in orbit around the Earth. ...

55 Cancri dust disk

In 1998 discovery a possible dust disk around 55 Cancri A was announced. Calculations gave the disk radius at least 40 AU; also an inclination of 25° was measured. However, the discovery could not be verified and was later deemed spurious. 1998(MCMXCVIII) is a common year starting on Thursday of the Gregorian calendar, and was designated the International Year of the Ocean. ...

55 Cancri B

55 Cancri B is a faint 13th magnitude red dwarf. Spectral type of the star is M4 V. It orbits the brighter component at a distance of ~1065 AU, and one orbital revolution lasts tens of thousands of years at least. In astronomy, an epoch is a moment in time for which celestial coordinates or orbital elements are specified. ... This article is about the year 2000. ... Orion is a remarkable constellation, visible from most places on the globe (but not always the whole year long). ... When normal cells are damaged or old they undergo apoptosis; cancer cells, however, avoid apoptosis. ... Right ascension (RA; symbol α: Greek letter alpha) is the astronomical term for one of the two coordinates of a point on the celestial sphere when using the equatorial coordinate system. ... In astronomy, declination (dec) is one of the two coordinates of the equatorial coordinate system, the other being either right ascension or hour angle. ... A light year, abbreviated ly, is the distance light travels in one year: roughly 9. ... The parsec (symbol pc) is a unit of length used in astronomy. ... In astronomy, stellar classification is a classification of stars based initially on photospheric temperature and its associated spectral characteristics, and subsequenly refined in terms of other characteristics. ... The apparent magnitude (m) of a star, planet or other heavenly body is a measure of its apparent brightness; that is, the amount of light received from the object. ... Red Dwarf is a British science fiction comedy, created and originally written by Rob Grant and Doug Naylor. ... In astronomy, stellar classification is a classification of stars based initially on photospheric temperature and its associated spectral characteristics, and subsequenly refined in terms of other characteristics. ...

See also

• Bright stars between 10 and 15 Parsecs
• PSR 1257+12 - the smallest planets to date (2004)
• Extrasolar planet
• List of stars with confirmed extrasolar planets
• Planetary system

The list of nearest bright stars is a table of stars found near the Sun that have an absolute magnitude of +8. ... PSR 1257+12 (also catalogued as PSR B1257+12,PSR 1300+1240 and PSR J1300+1240) is a pulsar located 2630 light years from Earth. ... Infrared image of the star GQ Lupi (A) orbited by a planet (b) at a distance of approximately 20 times the distance between Jupiter and our Sun. ... The following are lists of stars with confirmed extrasolar planets. ... An artists concept of a protoplanetary disk. ...

References

• HD 75732. SIMBAD.  URL accessed on April 17, 2005.
• HD 75732 B. SIMBAD.  URL accessed on April 17, 2005.
• 55 Cnc B. SIMBAD.  URL accessed on April 17, 2005.
• 55 Cnc C. SIMBAD.  URL accessed on April 17, 2005.
• 55 Cnc D. SIMBAD.  URL accessed on April 17, 2005.
• 55 Cnc E. SIMBAD.  URL accessed on April 17, 2005.
• Notes for 55 Cnc. The Extrasolar Planets Encyclopaedia.  URL accessed on April 17, 2005.

April 17 is the 107th day of the year in the Gregorian calendar (108th in leap years). ... 2005 (MMV) is a common year starting on Saturday of the Gregorian calendar. ... April 17 is the 107th day of the year in the Gregorian calendar (108th in leap years). ... 2005 (MMV) is a common year starting on Saturday of the Gregorian calendar. ... April 17 is the 107th day of the year in the Gregorian calendar (108th in leap years). ... 2005 (MMV) is a common year starting on Saturday of the Gregorian calendar. ... April 17 is the 107th day of the year in the Gregorian calendar (108th in leap years). ... 2005 (MMV) is a common year starting on Saturday of the Gregorian calendar. ... April 17 is the 107th day of the year in the Gregorian calendar (108th in leap years). ... 2005 (MMV) is a common year starting on Saturday of the Gregorian calendar. ... April 17 is the 107th day of the year in the Gregorian calendar (108th in leap years). ... 2005 (MMV) is a common year starting on Saturday of the Gregorian calendar. ... April 17 is the 107th day of the year in the Gregorian calendar (108th in leap years). ... 2005 (MMV) is a common year starting on Saturday of the Gregorian calendar. ...

External links

• 55 Cancri from The Planet Project at the University of Illinois
• Astronomers searching for distant Earths find two Neptunes
• Extrasolar Visions entry