Editing Barnard's Star (section)

==== Astrometric planetary claims ====
For a decade from 1963 to about 1973, a substantial number of astronomers accepted a claim by [[Peter van de Kamp]] that he had detected, by using [[Methods of detecting exoplanets#Astrometry|astrometry]], a perturbation in the [[proper motion]] of Barnard's Star consistent with its having one or more planets comparable in mass with [[Jupiter]]. Van de Kamp had been observing the star from 1938, attempting, with colleagues at the [[Sproul Observatory]] at [[Swarthmore College]], to find minuscule variations of one [[micrometre]] in its position on [[photographic plate]]s consistent with [[perturbation (astronomy)|orbital perturbations]] that would indicate a planetary companion; this involved as many as ten people averaging their results in looking at plates, to avoid systemic individual errors.<ref name=Blunder>{{cite web|url=http://www.astrobio.net/index.php?option=com_retrospection&task=detail&id=1635|title=The Barnard's Star Blunder|date=July 2005|work=Astrobiology Magazine|access-date=26 January 2014 |url-status=usurped |archive-url=https://web.archive.org/web/20110804214004/http://www.astrobio.net/index.php?option=com_retrospection&task=detail&id=1635 |archive-date=2011-08-04}}</ref> 
Van de Kamp's initial suggestion was a planet having about {{Jupiter mass|1.6}} at a distance of 4.4{{nbsp}}AU in a slightly eccentric orbit,<ref>{{cite journal|last=van de Kamp|first=Peter|year=1963|title=Astrometric study of Barnard's star from plates taken with the 24-inch Sproul refractor|journal=[[The Astronomical Journal]]|volume=68|issue=7|page=515|bibcode=1963AJ.....68..515V|doi=10.1086/109001}}</ref> and these measurements were apparently refined in a 1969 paper.<ref>{{cite journal|last=van de Kamp|first=Peter|year=1969|title=Parallax, proper motion acceleration, and orbital motion of Barnard's Star|journal=[[The Astronomical Journal]]|volume=74|issue=2|page=238|bibcode=1969AJ.....74..238V|doi=10.1086/110799|doi-access=free}}</ref> Later that year, Van de Kamp suggested that there were two planets of 1.1 and {{Jupiter mass|0.8}}.<ref>{{cite journal|last=van de Kamp|first=Peter|date=August 1969|title=Alternate dynamical analysis of Barnard's star|journal=The Astronomical Journal|volume=74|issue=8|pages=757–759|bibcode=1969AJ.....74..757V|doi=10.1086/110852}}</ref>

[[Image:RedDwarfPlanet.jpg|thumb|right|Artist's conception of a planet in orbit around a red dwarf]]

Other astronomers subsequently repeated Van de Kamp's measurements, and two papers in 1973 undermined the claim of a planet or planets. [[George Gatewood]] and Heinrich Eichhorn, at a different observatory and using newer plate measuring techniques, failed to verify the planetary companion.<ref>{{cite journal|last1=Gatewood|first1=George|last2=Eichhorn|first2=H.|name-list-style=amp|year=1973|title=An unsuccessful search for a planetary companion of Barnard's star (BD +4 3561)|bibcode=1973AJ.....78..769G|journal=[[The Astronomical Journal]]|volume=78|issue=10|page=769|doi=10.1086/111480|doi-access=free}}</ref> Another paper published by John L. Hershey four months earlier, also using the Swarthmore observatory, found that changes in the astrometric field of various stars correlated to the timing of adjustments and modifications that had been carried out on the refractor telescope's objective lens;<ref>{{cite journal|first=John L.|last=Hershey|date=June 1973|title=Astrometric analysis of the field of AC +65 6955 from plates taken with the Sproul 24-inch refractor|journal=The Astronomical Journal|volume=78|issue=6|pages=421–425|bibcode=1973AJ.....78..421H|doi=10.1086/111436|doi-access=free}}</ref> the claimed planet was attributed to an artifact of maintenance and upgrade work. The affair has been discussed as part of a broader scientific review.<ref name=Bell>{{cite web|first=George H.|last=Bell|url=http://www.public.asu.edu/~sciref/exoplnt.htm|date=April 2001|title=The Search for the Extrasolar Planets: A Brief History of the Search, the Findings and the Future Implications|at=Section 2|publisher=Arizona State University|access-date=10 August 2006|archive-url=https://web.archive.org/web/20060813111219/http://www.public.asu.edu/~sciref/exoplnt.htm|archive-date=13 August 2006|url-status=live}} (Full description of the Van de Kamp planet controversy.)</ref>

Van de Kamp never acknowledged any error and published a further claim of two planets' existence as late as 1982;<ref>{{cite journal|last=Van de Kamp|first=Peter|year=1982|title=The planetary system of Barnard's star|journal=Vistas in Astronomy|volume=26|issue=2|page=141|bibcode=1982VA.....26..141V|doi=10.1016/0083-6656(82)90004-6}}</ref> he died in 1995. [[Wulff Heintz]], Van de Kamp's successor at Swarthmore and an expert on [[double star]]s, questioned his findings and began publishing criticisms from 1976 onwards. The two men were reported to have become estranged because of this.<ref name=Swathmore>{{cite web|first=Bill|last=Kent|url=http://media.swarthmore.edu/bulletin/wp-content/archived_issues_pdf/Bulletin_2001_03.pdf|title=Barnard's Wobble|pages=28–31|date=March 2001|work=Swarthmore College Bulletin|publisher=Swarthmore College|access-date=2 June 2010|url-status=dead|archive-url=https://web.archive.org/web/20110719124154/http://media.swarthmore.edu/bulletin/wp-content/archived_issues_pdf/Bulletin_2001_03.pdf|archive-date=19 July 2011}}</ref>