View source for 55 Cancri

{{Short description|Binary star with at least five exoplanets 41 light-years away}}
{{Good article}}
{{Starbox begin
| name = 55 Cancri
}}
{{Starbox image
| image =
{{Location mark
|image=Cancer constellation map.svg|alt=|float=center|width=260
|label=|position=right
|mark=Red circle.svg|mark_width=10|mark_link=55 Cnc
|x=416|y=222
}}
|caption=Location of 55 Cancri (circled in red)
}}
{{Starbox observe 2s
| epoch = J2000.0
| pronounce = {{IPAc-en|ˈ|k|æ|ŋ|k|r|aɪ}} or {{IPAc-en|ˈ|k|æ|ŋ|k|r|iː}}
| constell = [[Cancer (constellation)|Cancer]]
| component1 = 55 Cancri A
| ra1 = {{RA|08|52|35.8111}}<ref name=edr3a/>
| dec1 = {{DEC|+28|19|50.955}}<ref name=edr3a/>
| appmag_v1 = 5.95<ref name=vanbelle/>
| component2 = 55 Cancri B
| ra2 = {{RA|08|52|40.8627}}<ref name=edr3b/>
| dec2 = {{DEC|+28|19|58.821}}<ref name=edr3b/>
| appmag_v2 = 13.15<ref name=ucac4/>
}}
{{Starbox character
| component1 = 55 Cancri A
| type = Between [[main sequence]] and [[subgiant]]
| class = K0IV–V<ref name=nstars/>
| b-v = 0.87<ref name=hr/>
| u-b = 0.63<ref name=hr/>
| component2 = 55 Cancri B
| type2  = [[Main sequence]] ([[red dwarf]])
| class2 = M4.5V<ref name=carmenes/>
| b-v2 = 1.7<ref name=ucac4/>
| u-b2 =
}}
{{Starbox astrometry
| component1 = 55 Cancri A
| radial_v = 27.51<ref name=edr3a/>
| prop_mo_ra = {{Val|−485.681|0.040}}<ref name=edr3a/>
| prop_mo_dec = {{Val|−233.517|0.037}}<ref name=edr3a/>
| parallax = 79.4482
| p_error = 0.0429
| parallax_footnote = <ref name=edr3a/>
| absmag_v = +5.50<ref name=Anderson2012/>
| component2 = 55 Cancri B
| radial_v2 =
| prop_mo_ra2 = {{Val|−481.176|0.041}}<ref name=edr3b/>
| prop_mo_dec2 = {{Val|−244.544|0.032}}<ref name=edr3b/>
| parallax2 = 79.6560
| p_error2 = 0.0475
| parallax_footnote2 = <ref name=edr3b/>
| absmag_v2 = +{{Val|12.58|0.088}}<ref name=houdebine/>
}}
{{Starbox detail
| component1 = 55 Cnc A
| mass = {{Val|0.905|0.015}}<ref name="vonbraun2011"/>
| radius = {{Val|0.943|0.010}}<ref name="vonbraun2011"/>
| luminosity = {{Val|0.582|0.014}}<ref name="vonbraun2011"/>
| temperature = {{Val|5172|18|fmt=commas}}<ref name="Bourrier2018"/>
| metal_fe = {{Val|0.35|0.10}}<ref name=Bourrier2018/>
| gravity = {{Val|4.45|0.01}}<ref name="vonbraun2011"/>
| rotation = {{Val|38.8|0.05}} [[day]]s<ref name=Bourrier2018/>
| rotational_velocity = <{{Val|1.23|0.01}}<ref name=Bourrier2018/>
| age_gyr = {{Val|8.6|1}}<ref name="Bourrier2018"/>
| component2 = 55 Cnc B
| mass2 = {{Val|0.264|0.007}}<ref name=Carmenes2019/>
| radius2 = {{Val|0.268|0.009}}<ref name=Carmenes2019/>
| luminosity2 = 0.00788{{±|0.00013}}<ref name=Carmenes2019/>
| temperature2 = {{Val|3,320|51|fmt=commas}}<ref name=Carmenes2019/>
| metal2_fe = 0.15{{±|0.16}}<ref name=Carmenes2019/>
| rotation2 = {{Val|6.11|3.2|1.9}} [[day]]s<ref name=houdebine/>
| rotational_velocity2 = {{Val|2.36}}<ref name=houdebine/>
}}
{{Starbox catalog
| names = {{odlist | name=Copernicus | B=Rho<sup>1</sup>&nbsp;Cancri | F=55&nbsp;Cnc | GJ=324 | BD=+28°1660 | HD=75732 | HIP=43587 | HR=3522 | SAO=80585 }}
}}
{{Starbox reference
| Simbad = 55+Cnc
| Simbad2 = 55+Cnc+B |sn2=55 Cnc B
| EPE = 55+Cnc
| ARICNS = 00669
| NSTED = 55+Cnc
}}
{{Starbox end}}
'''55 Cancri''' is a [[binary star]] system located 41<ref name=edr3a/>&nbsp;[[light-year]]s away from the [[Sun]] in the [[zodiac]] [[constellation]] of [[Cancer (constellation)|Cancer]]. It has the [[Bayer designation]] '''Rho<sup>1</sup>&nbsp;Cancri''' (ρ<sup>1</sup>&nbsp;Cancri); ''55 Cancri'' is the [[Flamsteed designation]] (abbreviated 55 Cnc). The system consists of a [[K-type star]] (designated 55 Cancri A, also named '''Copernicus''' {{IPAc-en|k|ou|'|p|3r|n|I|k|@|s}})<ref name="IAU-CSN"/> and a smaller [[red dwarf]] (55 Cancri B).
{{As of|2015}}, five [[extrasolar planet]]s (designated [[55 Cancri b]], [[55 Cancri c|c]], [[55 Cancri d|d]], [[55 Cancri e|e]] and [[55 Cancri f|f]]; named Galileo, Brahe, Lipperhey, Janssen and Harriot, respectively) are known to [[orbit]] 55 Cancri A.
==Nomenclature==
55 Cancri is the system's [[Flamsteed designation]]. It also bears the [[Bayer designation]] ρ<sup>1</sup> Cancri ([[Latinisation of names|Latinised]] to Rho<sup>1</sup> Cancri) and the [[Bright Star Catalogue]] designation HR&nbsp;3522. The two components are designated A and B,<ref name="Raghavan2006"/> though component A is sometimes referred to simply as 55 Cancri.<ref name="Marcy2002"/> The first planet discovered orbiting 55 Cancri A was designated HR 3522b by its discoverers,<ref name="Butler1997"/> though it is more commonly referred to as 55 Cancri b.<ref name="EPE55Canb"/> Under the rules for naming objects in binary star systems it should be named 55 Cancri Ab<ref name="WMC"/> and this more formal form is occasionally used to avoid confusion with the secondary star 55&nbsp;Cancri&nbsp;B. The other planets discovered were designated 55 Cancri c, d, e and f, in order of their discovery.
In July 2014 the [[International Astronomical Union]] launched [[NameExoWorlds]], a process for giving proper names to certain exoplanets and their host stars.<ref>[http://www.iau.org/news/pressreleases/detail/iau1404/ NameExoWorlds: An IAU Worldwide Contest to Name Exoplanets and their Host Stars]. IAU.org. 9 July 2014</ref> The process involved public nomination and voting for the new names.<ref>{{Cite web |url=http://nameexoworlds.iau.org/process |title=NameExoWorlds The Process |access-date=2015-09-05 |archive-date=2015-08-15 |archive-url=https://web.archive.org/web/20150815025117/http://www.nameexoworlds.iau.org/process |url-status=dead }}</ref> In December 2015, the IAU announced the winning names were Copernicus for 55 Cancri A and Galileo, Brahe, Lipperhey, Janssen and Harriot for its planets (b, c, d, e and f, respectively).<ref name="IAUresults">[http://www.iau.org/news/pressreleases/detail/iau1514/ Final Results of NameExoWorlds Public Vote Released], International Astronomical Union, 15 December 2015.</ref>
The winning names were those submitted by the Royal Netherlands Association for Meteorology and Astronomy of the [[Netherlands]]. They honor the astronomers [[Nicolaus Copernicus]], [[Galileo Galilei]], [[Tycho Brahe]] and [[Thomas Harriot]] and the spectacle makers and telescope pioneers [[Hans Lippershey|Hans Lipperhey]] and [[Zacharias Janssen|Jacharias Janssen]].<ref name="IAUnames">{{Cite web |url=http://nameexoworlds.iau.org/names |title=NameExoWorlds The Approved Names |access-date=2015-12-27 |archive-date=2018-02-01 |archive-url=https://web.archive.org/web/20180201043609/http://nameexoworlds.iau.org/names |url-status=dead }}</ref> (The IAU originally announced the winning name was Lippershey for 55 Cancri d. In January 2016, in recognition that his actual name was Lipperhey (with Lippershey an error introduced in the 19th century), the exoplanet name was corrected to Lipperhey by the IAU and that name was submitted to the official sites that keep track of astronomical information).<ref name="IAUresults"/><ref name="IAUnames"/>
In 2016, the IAU organized a [[Working Group on Star Names]] (WGSN)<ref name="WGSN"/> to catalog and standardize proper names for stars. In its first bulletin of July 2016,<ref name="WGSN1"/> the WGSN explicitly recognized the names of exoplanets and their host stars approved by the Executive Committee Working Group Public Naming of Planets and Planetary Satellites, including the names of stars adopted during the 2015 NameExoWorlds campaign. This star is now so entered in the IAU Catalog of Star Names.<ref name="IAU-CSN"/>
==Stellar system==
The 55 Cancri system is located fairly close to the [[Solar System]]: the [[Gaia (spacecraft)|''Gaia'']] [[astrometry]] [[satellite]] measured the [[parallax]] of 55 Cancri A as 79.45 [[milliarcseconds]], corresponding to a distance of {{convert|12.6|pc|ly|abbr=off|lk=on}}.<ref name="edr3a" /> 55 Cancri A has an [[apparent magnitude]] of 5.95, making it just visible to the [[naked eye]] under very dark skies. The red dwarf 55 Cancri B is of the 13th magnitude and only visible through a [[telescope]]. The two components are separated by {{val|85|ul="}}, an estimated separation of {{Val|1065|fmt=commas|ul=AU}}<ref name="Eggenberger2003" /> (6.15 [[light-day]]s). Despite their wide separation, the two stars appear to be gravitationally bound, as they share a common [[proper motion]].<ref name="Marcy2002"/>
===55 Cancri A===
The primary star, 55 Cancri A, has a [[spectral type]] of K0IV-V, indicating a [[main-sequence]] or [[subgiant]] star. It is smaller in radius and slightly less massive than the [[Sun]], and so is cooler and less [[luminosity|luminous]]. The star has only low emission from its chromosphere, and is not variable in the visible spectrum;<ref name="Marcy2002"/> but it is variable in X-rays.<ref name=transitatmo/> It is more enriched than the Sun in [[Heavy metals|elements heavier]] than [[helium]], with 186% the solar abundance of [[iron]]; it is therefore classified as a rare "super [[metal-rich]]" (SMR) star.<ref name="Marcy2002"/> 55 Cancri A also has more carbon than the Sun, with a C/O ratio of 0.78,<ref name=teske2013/> compared to solar value of 0.55. This abundance of metal makes estimating the star's age and mass difficult, as [[stellar evolution|evolutionary]] models are less well defined for such stars.{{Citation needed|date=April 2014}} 55 Cancri A is much older than the solar system, and its age has been estimated to values of 7.4–8.7 billion years<ref name="apj687"/> or 10.2 ± 2.5 billion years.<ref name="vonbraun2011"/>
A hypothesis for the high metal content in SMR dwarf stars is that material enriched in heavy elements fell into the atmosphere from a [[protoplanetary disk]]. This would pollute the star's external layers, resulting in a higher than normal metallicity. The lack of a deep [[convection zone]] would mean that the outer layers would retain higher abundance ratios of these heavy elements.<ref name=pasquini2007/>
Observations of 55 Cancri A in the [[Submillimetre astronomy|submillimeter]] region of the spectrum have thus far failed to detect any associated dust. The upper limit on emissions within {{val|100|u=AU}} of this star is about 850&nbsp;[[Jansky|mJy]], at a wavelength of 850&nbsp;μm. This limits the total mass of fine dust around the star to less than 0.01% of the Earth's mass. However, this does not exclude the presence of an asteroid belt or a [[Kuiper belt]] equivalent.<ref name="Jayawardhana2002"/>
===55 Cancri B===
The secondary, 55 Cancri B, is a [[red dwarf]] star much less massive and luminous than the Sun. There are indications that component B may itself be a double star, though this is uncertain.<ref name="Raghavan2006"/>
==Planetary system==
{{OrbitboxPlanet begin
| name=55 Cancri A
| table_ref= <ref name="Winn2011"/><ref name=dawson2010/><ref name=Bourrier2018/>
}}
{{OrbitboxPlanet
| exoplanet = [[55 Cancri e|e (Janssen)]]
| mass_earth = 7.99{{±|0.32|0.33}}
| period = 0.73654625{{±|0.00000015}}<ref name="Kokori2023"/>
| semimajor = 0.01544 ± 0.00005
| eccentricity = 0.05 ± 0.03
| inclination = 83.59{{±|0.47|0.44}}
| radius_earth = 1.875 ± 0.029
}}
{{OrbitboxPlanet
| exoplanet = [[55 Cancri b|b (Galileo)]]
| mass = ≥{{Val|0.8036|0.0092|0.0091}}
| period = 14.6516 ± 0.0001
| semimajor = 0.1134 ± 0.0006
| eccentricity = 0 ± 0.01
| inclination = ~85
}}
{{OrbitboxPlanet
| exoplanet = [[55 Cancri c|c (Brahe)]]
| mass_earth = ≥51.2 ± 1.3
| period = {{Val|44.3989|0.0042|0.0043}}
| semimajor = 0.2373 ± 0.0013
| eccentricity = 0.03 ± 0.02
}}
{{OrbitboxPlanet
| exoplanet = [[55 Cancri f|f (Harriot)]]
| mass_earth = ≥47.8 ± 2.4
| period = 259.88 ± 0.29
| semimajor = {{Val|0.7708|0.0043|0.0044}}
| eccentricity = {{Val|0.08|0.05|0.04}}
}}
{{OrbitboxPlanet
| exoplanet = [[55 Cancri d|d (Lipperhey)]]
| mass = ≥3.12 ± 0.10
| period = {{Val|5,574.2|93.8|88.6|fmt=commas}}
| semimajor = {{Val|5.957|0.074|0.071}}
| eccentricity = 0.13 ± 0.02
}}
{{Orbitbox end}}
[[File:55CncInnerOrbits.svg|thumb|right|Comparison of the orbits of the inner planets of 55 Cancri A (black) with the planets of the Solar System]]
The 55 Cancri system was the first known to have four, and later five, planets, and may possibly have more. The innermost planet, e, [[Transit (astronomy)|transits]] 55 Cancri A as viewed from Earth.<ref name="Winn2011"/> The next planet, b, is non-transiting but there is tentative evidence that it is surrounded by an extended atmosphere that does transit the star.<ref name=transitatmo/>
In 1997, the discovery of a [[51 Pegasi]]-like planet [[orbit]]ing 55 Cancri A was announced, together with the planet of [[Tau Boötis]] and the inner planet of [[Upsilon Andromedae]].<ref name="Butler1997"/> The planet was discovered by measuring the star's [[radial velocity]], which showed a periodicity of around 14.7 days corresponding to a planet at least 78% of the [[mass of Jupiter]]. These radial velocity measurements still showed a drift unaccounted for by this planet, which could be explained by the [[gravitational]] influence of a more distant object.
In 1998 the discovery of a possible dust disk around 55 Cancri A was announced.<ref name="Trilling1998"/> Calculations gave the disk radius at least 40&nbsp;AU, similar to the [[Kuiper belt]] in the Solar System, with an inclination of 25° with respect to the plane of the sky. However, the discovery could not be verified and was later deemed to be spurious, caused instead by background galaxies.<ref name="Schneider2001"/>
[[File:Extrasolar planet NASA2.jpg|thumb|The [[Solar System]] with only [[Earth]] and [[Jupiter]] compared with the planetary system of 55 Cancri (Note: this depiction was made before planets e and f were discovered.)]]
After making further radial velocity measurements, a planet orbiting at a distance of around 5 AU was announced in 2002.<ref name="Marcy2002"/> This planet received the designation [[55 Cancri d]]. At the time of discovery, the planet was thought to be in an orbit of mild [[Orbital eccentricity|eccentricity]] (close to 0.1), but this value was increased by later measurements. Even after accounting for these two planets, a periodicity at 43 days remained, possibly due to a third planet. Measurements of the star suggested that this was close to the star's rotation period, which raised the possibility that the 43-day signal was caused by stellar activity. This possible planet received the designation [[55 Cancri c]].
[[File:55Cnc system.jpg|thumb|left|Artist's rendition of 55 Cnc's planets]]
[[55 Cancri e]] was announced in 2004.<ref name="McArthur2004"/> With 8.3 Earth masses, it is a large [[super-Earth]] which was originally thought to have an orbital period of 2.8 days, though it was later found that this was an alias of its true period of 0.74 of a day by observations of e [[planetary transit|transiting]] in 2011.<ref name="Winn2011"/> This planet was the first known instance of a fourth extrasolar planet in one system, and was the shortest-period planet until the discovery of [[PSR J1719−1438 b]]. The measurements that led to the discovery of this planet also confirmed the existence of 55 Cancri c.
In 2005, [[Jack Wisdom]] combined three data sets and drew two distinct conclusions: that the 2.8-day planet was an alias and that there was a [[Neptune]]-scale planet with a period near 261 days. Fischer et al. (2008)<ref name=fischer2008/> reported new observations that they said confirmed the existence of the 2.8-day planet, as first reported by McArthur et al. (2004), and a 260-day Neptune-sized planet, as first reported by Wisdom (2005).<ref name=wisdom/> However, Dawson and Fabrycky (2010)<ref name=dawson2010/> concluded that the 2.8-day planet was indeed an alias, as suggested by Wisdom (2005), and that the correct period was 0.7365 of a day.
In 2007, Fisher et al. confirmed the existence of the 260-day planet proposed in 2005 by Wisdom. This planet, 55 Cancri f, was the first occurrence of a fifth extrasolar planet in one system. With a similar mass to [[55 Cancri c|c]], it has a 260-day orbit, towards the inner edge of 55 Cancri A's [[habitable zone]].<ref name="ScienceDaily"/><ref name="Fischer2008"/> The planet itself is not thought to be conducive to life, but hypothetical [[Exomoon|moons]] in principle could maintain at least water and life.
The planet e's eccentricity is poorly defined; varying values between 0 and 0.4 does not significantly improve the fit, so an eccentricity of 0.2 was assumed. Taking interactions between the planets into account results in a near-zero orbital eccentricity.
Astrometric observations with the [[Hubble Space Telescope]] measured an inclination of 53° of the outer planet d,<ref name="McArthur2004"/> though this result relies on the precise orbital parameters which have been substantially revised since this was published.<ref name="Nelson2014"/> The observed transits of e suggest an orbit normal inclined within 9° to the line-of-sight, and a possible detection of the transit of an extended atmosphere around 55 Cancri b would, if confirmed, imply that it too is in an orbit that is close to edge-on.<ref name=transitatmo/> Between them, no measurement of c's nor f's inclinations have been made. It had been thought that with five planets, the system cannot deviate far from [[coplanar]] in order to maintain stability.<ref name="Fischer2008"/> An attempt to measure the spin-orbit misalignment of the innermost planet reported that it was in a nearly polar orbit,<ref name=bourrier2014/> but this interpretation of the data has since been challenged by a subsequent study, with noted inconsistencies between the implied and measured stellar rotation.<ref name=lm2014/>
The approximate ratios of periods of adjacent orbits are (proceeding outward): 1:20, 1:3, 1:6, 1:20. The nearly 1:3 ratio between 55 Cancri b and c is apparently a [[orbital resonance#Coincidental 'near' ratios of mean motion|near resonance]], rather than a genuine [[mean motion resonance]].<ref name="Fischer2008"/>
=== Possible additional planets ===
Between planets f and d, there appears to be a huge gap of distance where no planets are known to orbit. A 2008 paper found that as many as 3 additional planets of up to 50 times the mass of Earth could orbit at a distance of 0.9 to 3.8 AU from the star, and stable resonances of a hypothetical planet g with the known planets were found to be 3f:2g, 2g:1d, and 3g:2d.<ref name="Raymond2008"/> A study released in 2019 showed that undiscovered terrestrial planets may be able to orbit safely in this region at 1 to 2 AU; this space includes the outer limits of 55 Cancri's [[habitable Zone]].<ref name="Satyal2019"/>
In 2021, it was found that terrestrial planets with comparable water content to Earth may have indeed been able to form and survive between the planets f and d.<ref name="Zhou2021"/>
As for the space outside d's orbit, its stability zone begins beyond 10 AU, though there is a stability zone between 8.6 and 9 AU due to a 2:1 resonance.<ref name="Raymond2008"/>
===Search for Radio Emissions===
Since 55 Cancri e orbits less than 0.1 AU from its host star, some scientists hypothesized that it may cause stellar flaring synchronized to the orbital period of the exoplanet.  A 2011 search for these magnetic star-planet interactions that would result in [[Stellar_corona|coronal]] radio emissions resulted in no detected signal.  Furthermore, no [[Magnetosphere|magnetospheric]] radio emissions were detected from any exoplanet within the system.<ref>{{cite journal|last1=Route|first1=Matthew|last2=Wolszczan|first2=Alex|title=ROME. III. The Arecibo Search for Star–Planet Interactions at 5 GHz|journal=The Astrophysical Journal|date=1 August 2023|volume=952|issue=2|page=118|doi=10.3847/1538-4357/acd9ad|arxiv=2202.08899|bibcode=2023ApJ...952..118R|doi-access=free }}</ref>
==Communication==
A [[Active SETI|METI]] message was sent to 55 Cancri. It was transmitted from [[Eurasia]]'s largest [[radar]]—the {{cvt|70|m}} [[Evpatoria Planetary Radar]]. The message was named [[Cosmic Call 2]]; it was sent on July 6, 2003, and it will arrive at 55 Cancri in May 2044.<ref name="Cosmic"/>
==See also==
* [[58 Cancri]], or Rho<sup>2</sup> Cancri (ρ<sup>2</sup> Cnc)
* [[Sudarsky's gas giant classification]]
* [[Cancer in Chinese astronomy]]
* [[Kepler-186]]
* [[Lists of exoplanets]]
* [[Gliese 1132 b]] – rocky exoplanet with a confirmed atmosphere
* [[Mu Arae c]] – At constellation Ara
* [[Planetary system]]
* [[PSR B1257+12]]
==References==
{{Reflist|refs=
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<ref name=Carmenes2019>{{cite journal
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<ref name="Cosmic">{{Cite web | title=Передача и поиски разумных сигналов во Вселенной | url=http://www.cplire.ru/rus/ra%26sr/VAK-2004.html | publisher=Cplire.ru | access-date=2008-09-14 | archive-date=2019-05-30 | archive-url=https://web.archive.org/web/20190530145209/https://www.plover.com/misc/Dumas-Dutil/messages.pdf | url-status=dead }}</ref>
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<ref name="Eggenberger2003">{{Cite journal | title=Planets in Binaries | last1=Eggenberger | first1=A. | last2=Udry | first2=S. | last3=Mayor | first3=M. | display-authors=1 | journal=Scientific Frontiers in Research on Extrasolar Planets | date=2003 | volume=294 | pages=43–46 | bibcode=2003ASPC..294...43E }}</ref>
<ref name="EPE55Canb">{{cite encyclopedia | url=https://exoplanet.eu/catalog/55_cnc_b--25/ | title=Notes for Planet 55 Cnc b | author=Jean Schneider | date=2011 | encyclopedia=[[Extrasolar Planets Encyclopaedia]] | access-date=8 October 2011 }}</ref>
<ref name="Fischer2008">{{Cite journal | title=Five Planets Orbiting 55 Cancri | last1=Fischer | first1=Debra A. | last2=Marcy | first2=Geoffrey W. | last3=Butler | first3=R. Paul | last4=Vogt | first4=Steven S. | last5=Laughlin | first5=Greg | last6=Henry | first6=Gregory W. | last7=Abouav | first7=David | last8=Peek | first8=Kathryn M. G. | last9=Wright | first9=Jason T. | display-authors=1 | journal=The Astrophysical Journal | volume=675 | issue=1 | pages=790–801 | year=2008 | arxiv=0712.3917 | bibcode=2008ApJ...675..790F | doi=10.1086/525512 | s2cid=55779685 }}</ref>
<ref name=edr3a>{{Cite Gaia EDR3|704967037090946688}}</ref>
<ref name=edr3b>{{cite Gaia EDR3|704966762213039488}}</ref>
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}}
==Further reading==
* {{cite journal|last1=Ji|first1=Jianghui|last2=Kinoshita|first2=Hiroshi|last3=Liu|first3=Lin|last4=Li|first4=Guangyu|title=Could the 55 Cancri Planetary System Really Be in the 3[rcolon]1 Mean Motion Resonance?|journal=The Astrophysical Journal|volume=585|issue=2|date=2003|pages=L139–L142|issn=0004-637X|doi=10.1086/374391|arxiv = astro-ph/0301636 |bibcode = 2003ApJ...585L.139J |s2cid=15993774}}
* {{cite journal|last1=Schneider|first1=G.|last2=Becklin|first2=E. E.|last3=Smith|first3=B. A.|last4=Weinberger|first4=A. J.|last5=Silverstone|first5=M.|last6=Hines|first6=D. C.|title=NICMOS Coronagraphic Observations of 55 Cancri|journal=The Astronomical Journal|volume=121|issue=1|date=2001|pages=525–537|issn=0004-6256|doi=10.1086/318050|arxiv = astro-ph/0010175 |bibcode = 2001AJ....121..525S |s2cid=14503540}}
* {{cite journal|last1=Jayawardhana|first1=Ray|last2=Holland|first2=Wayne S.|last3=Kalas|first3=Paul|last4=Greaves|first4=Jane S.|last5=Dent|first5=William R. F.|last6=Wyatt|first6=Mark C.|last7=Marcy|first7=Geoffrey W.|title=New Submillimeter Limits on Dust in the 55 Cancri Planetary System|journal=The Astrophysical Journal|volume=570|issue=2|date=2002|pages=L93–L96|issn=0004-637X|doi=10.1086/341101|arxiv = astro-ph/0204140 |bibcode = 2002ApJ...570L..93J |s2cid=15516278}}
* {{cite journal|last1=Zhou|first1=Li-Yong|last2=J. Lehto|first2=Harry|last3=Sun|first3=Yi-Sui|last4=Zheng|first4=Jia-Qing|title=Apsidal corotation in mean motion resonance: the 55 Cancri system as an example|journal=[[Monthly Notices of the Royal Astronomical Society]]|volume=350|issue=4|date=2004|pages=1495–1502|issn=0035-8711|doi=10.1111/j.1365-2966.2004.07755.x|doi-access=free |arxiv = astro-ph/0310121 |bibcode = 2004MNRAS.350.1495Z |s2cid=16821093}}
* {{cite journal|last1=Jayawardhana|first1=Ray|last2=Holland|first2=Wayne S.|last3=Greaves|first3=Jane S.|last4=Dent|first4=William R. F.|last5=Marcy|first5=Geoffrey W.|last6=Hartmann|first6=Lee W.|last7=Fazio|first7=Giovanni G.|title=Dust in the 55 Cancri Planetary System|journal=The Astrophysical Journal|volume=536|issue=1|date=2000|pages=425–428|issn=0004-637X|doi=10.1086/308942|arxiv = astro-ph/0001275 |bibcode = 2000ApJ...536..425J |s2cid=44777812}}
* {{cite journal|last1=Rasio|first1=F. A.|last2=Ford|first2=E. B.|title=Dynamical Instabilities and the Formation of Extrasolar Planetary Systems|journal=Science|volume=274|issue=5289|date=1996|pages=954–956|issn=0036-8075|doi=10.1126/science.274.5289.954|pmid=8875930|bibcode = 1996Sci...274..954R |s2cid=2940958}}
* {{cite journal|last1=von Bloh|first1=W.|last2=Cuntz|first2=M.|last3=Franck|first3=S.|last4=Bounama|first4=C.|title=On the Possibility of Earth-Type Habitable Planets in the 55 Cancri System|journal=Astrobiology|volume=3|issue=4|date=2003|pages=681–688|issn=1531-1074|doi=10.1089/153110703322736015|bibcode = 2003AsBio...3..681V|pmid=14987474}}
* {{cite journal|last1=Ji|first1=Jiang-Hui|last2=Kinoshita|first2=Hiroshi|last3=Liu|first3=Lin|last4=Li|first4=Guang-Yu|title=The dynamical architecture and habitable zones of the quintuplet planetary system 55 Cancri|journal=Research in Astronomy and Astrophysics|volume=9|issue=6|date=2009|pages=703–711|issn=1674-4527|doi=10.1088/1674-4527/9/6/009|arxiv = 0902.4328 |bibcode = 2009RAA.....9..703J |s2cid=15304622}}
* {{cite journal|last1=Raymond|first1=Sean N.|last2=Barnes|first2=Rory|last3=Gorelick|first3=Noel|title=A Dynamical Perspective on Additional Planets in 55 Cancri|journal=The Astrophysical Journal|volume=689|issue=1|date=2008|pages=478–491|issn=0004-637X|doi=10.1086/592772|arxiv = 0808.3295 |bibcode = 2008ApJ...689..478R |s2cid=941288}}
* {{cite journal|last1=Marzari|first1=F.|last2=Scholl|first2=H.|last3=Tricarico|first3=P.|title=Frequency map analysis of the 3/1 resonance between planets b and c in the 55 Cancri system|journal=Astronomy and Astrophysics|volume=442|issue=1|date=2005|pages=359–364|issn=0004-6361|doi=10.1051/0004-6361:20053164|bibcode = 2005A&A...442..359M |doi-access=free|url=https://hal.archives-ouvertes.fr/hal-00388290/file/aa3164-05.pdf}}
==External links==
{{Commons category}}
* {{Cite web|url=http://www.solstation.com/stars2/55cnc2.htm |title=55 (Rho1) Cancri 2 |access-date=2008-06-12 |work=SolStation| archive-url= https://web.archive.org/web/20080625041651/http://www.solstation.com/stars2/55cnc2.htm| archive-date= 25 June 2008 | url-status= live}}
* {{cite encyclopedia |url=http://exoplanet.eu/star.php?st=55+Cnc |archive-url=https://web.archive.org/web/20070929083145/http://exoplanet.eu/star.php?st=55+Cnc |url-status=dead |archive-date=September 29, 2007 |title=Notes for star 55 Cnc |author=Jean Schneider |date=2011 |encyclopedia=[[Extrasolar Planets Encyclopaedia]] |access-date=8 October 2011}}
* {{Cite web |url=http://www.astro.uiuc.edu/~kaler/sow/55cnc.html |title=55 Cancri |access-date=2008-06-12 |work=[[University of Illinois]] |publisher=The Planet Project |archive-url=https://web.archive.org/web/20080517225606/http://www.astro.uiuc.edu/~kaler/sow/55cnc.html |archive-date=17 May 2008 |url-status=dead }}
* {{Cite web|url=http://www.berkeley.edu/news/media/releases/2004/08/31_neptune.shtml |title=Astronomers searching for distant Earths find two Neptunes |access-date=2008-06-12 |last=Sanders |first=Robert |date=2004-08-31 |work=UC Berkeley News| archive-url= https://web.archive.org/web/20080516172736/http://www.berkeley.edu/news/media/releases/2004/08/31_neptune.shtml| archive-date= 16 May 2008 | url-status= live}}
* {{Cite web |url=http://starrymirror.com/5thplanetorbitingstar.htm |title=Astronomers Find Fifth Planet Around 55 Cancri |access-date=2008-06-12 |author=Ward Glen |date=2007-11-08 |work=The Starry Mirror |url-status=dead |archive-url=https://web.archive.org/web/20071110000646/http://starrymirror.com/5thplanetorbitingstar.htm |archive-date=2007-11-10 }}
* [http://www.aphelion-webzine.com/shorts/2008/08/WhentheGodsFall.html When the Gods Fall] 55 Cancri in fiction.
* [http://www.lpl.arizona.edu/~rory/research/xsp/dynamics/ Extrasolar Planet Interactions] {{Webarchive|url=https://web.archive.org/web/20160505160348/http://www.lpl.arizona.edu/~rory/research/xsp/dynamics/ |date=2016-05-05 }} by Rory Barnes & Richard Greenberg, Lunar and Planetary Lab, University of Arizona
* [https://www.youtube.com/watch?v=ymkxJLg5GGg The First] and [https://www.youtube.com/watch?v=gk6TY2uoASY the second part] of a computer animation of the 55 Cancri planetary system.
* [https://thehappykoala.github.io/Harmony-of-the-Spheres/#/category/McDonald/scenario/55%20Cnc Interactive visualisation of the 55 Cancri system]
{{Sky|08|52|35.8||28|19|51|40900}}
{{55 Cancri}}
{{Stars of Cancer}}
{{Portal bar|Astronomy|Stars|Spaceflight|Outer space|Solar System}}
{{DEFAULTSORT:55 Cancri}}
[[Category:55 Cancri| ]]
[[Category:Bayer objects|Cancri, Rho1]]
[[Category:Binary stars]]
[[Category:Cancer (constellation)]]
[[Category:Durchmusterung objects|BD+28 1660]]
[[Category:Flamsteed objects|Cancri, 55]]
[[Category:K-type main-sequence stars]]
[[Category:Solar analogs|Cancri, 55]]
[[Category:Gliese and GJ objects|0324]]
[[Category:Henry Draper Catalogue objects|075732]]
[[Category:Hipparcos objects|043587]]
[[Category:Bright Star Catalogue objects|3522]]
[[Category:Planetary systems with five confirmed planets]]
[[Category:Planetary transit variables]]
[[Category:Multi-star planetary systems|2]]
[[Category:K-type subgiants]]