Nomads of the Galaxy, Louis E. Strigari, Matteo Barnabe, Philip J. Marshall, Roger D. Blandford의 연구에 따르면 태양질량 0.08~1배 사이 주계열성 1개당 태양질량 10−6배(화성 질량 정도)보다 큰 천체 700개가 존재한다고 한다. 이 경우 우리 은하 내 행성 수는 수십억 개는 된다.
William J. Borucki (2010년 7월 23일). “Characteristics of Kepler Planetary Candidates Based on the First Data Set: The Majority are Found to be Neptune-Size and Smaller”. arXiv:1012.0707v2.
A.P. Hatzes; Cochran, William D.; Endl, Michael; McArthur, Barbara; Paulson, Diane B.; Walker, Gordon A. H.; Campbell, Bruce; Yang, Stephenson (2003). “A Planetary Companion to Gamma Cephei A”. 《Astrophysical Journal》 599 (2): 1383–1394. arXiv:astro-ph/0305110. Bibcode:2003ApJ...599.1383H. doi:10.1086/379281.
Laurence R. Doyle; Carter, J. A.; Fabrycky, D. C.; Slawson, R. W.; Howell, S. B.; Winn, J. N.; Orosz, J. A.; Pr Sa, A.; Welsh, W. F. (2011년 9월 16일). “Kepler-16: A Transiting Circumbinary Planet”. 《Science》 333 (6049): 1602–6. arXiv:1109.3432. Bibcode:2011Sci...333.1602D. doi:10.1126/science.1210923. PMID21921192.
Batalha, Natalie; Rowe; Bryson; Burke; Caldwell; Christiansen; Thompson (2012년 2월 27일). “Planetary Candidates observed by Kepler III:Analysis of the first 16 Months of Data”. arXiv:1202.5852.
Rodigas, Timothy (2009). “Which Radial Velocity Exoplanets Have Undetected Outer Companions?” v1판. arXiv:0907.0020.|확인날짜=는 |url=을 필요로 함 (도움말)
Eric, Hand (2011년 12월 20일). “Kepler discovers first Earth-sized exoplanets”. 《Nature》. doi:10.1038/nature.2011.9688.
See, Thomas Jefferson Jackson (1896). “Researches on the Orbit of F.70 Ophiuchi, and on a Periodic Perturbation in the Motion of the System Arising from the Action of an Unseen Body”. 《The Astronomical Journal》 16: 17. doi:10.1086/102368.
Campbell, B.; Walker, G. A. H.; Yang, S. (1988). “A search for substellar companions to solar-type stars”. 《The Astrophysical Journal》 331: 902. doi:10.1086/166608.
G.A.H. Walker; Bohlender, David A.; Walker, Andrew R.; Irwin, Alan W.; Yang, Stephenson L. S.; Larson, Ana (1992). “Gamma Cephei – Rotation or planetary companion?”. 《Astrophysical Journal Letters》 396 (2): L91–L94. Bibcode:1992ApJ...396L..91W. doi:10.1086/186524.
A.P. Hatzes; Cochran, William D.; Endl, Michael; McArthur, Barbara; Paulson, Diane B.; Walker, Gordon A. H.; Campbell, Bruce; Yang, Stephenson (2003). “A Planetary Companion to Gamma Cephei A”. 《Astrophysical Journal》 599 (2): 1383–1394. arXiv:astro-ph/0305110. Bibcode:2003ApJ...599.1383H. doi:10.1086/379281.
Laurence R. Doyle; Carter, J. A.; Fabrycky, D. C.; Slawson, R. W.; Howell, S. B.; Winn, J. N.; Orosz, J. A.; Pr Sa, A.; Welsh, W. F. (2011년 9월 16일). “Kepler-16: A Transiting Circumbinary Planet”. 《Science》 333 (6049): 1602–6. arXiv:1109.3432. Bibcode:2011Sci...333.1602D. doi:10.1126/science.1210923. PMID21921192.
Bonfils, X.; Forveille, T.; Delfosse, X.; 외. (2005). “The HARPS search for southern extra-solar planets VI: A Neptune-mass planet around the nearby M dwarf Gl 581”. 《Astronomy & Astrophysics》 443: L15 – L18. doi:10.1051/0004-6361:200500193.
Sato, B.; Fischer, D.; Henry, G.; Laughlin, G.; Butler, R.; Marcy, G.; Vogt, S.; Bodenheimer, P.; Ida, S.; Toyota, E.; Wolf, A.; Valenti, J.; Boyd, L.; Johnson, J.; Wright, J.; Ammons, M.; Robinson, S.; Strader, J.; McCarthy, C.; Tah, K.; Minniti, D. (2005). “The N2K Consortium II: A Transiting Hot Saturn around HD 149026 with a Large Dense Core”. 《The Astrophysical Journal》 633: 465 – 473. doi:10.1086/449306.
J.P. Beaulieu; D.P. Bennett; P. Fouque; A. Williams; M. Dominik; U.G. Jorgensen; D. Kubas; A. Cassan; C. Coutures; J. Greenhill; K. Hill; J. Menzies; P.D. Sackett; M. Albrow; S. Brillant; J.A.R. Caldwell; J.J. Calitz; K.H. Cook; E. Corrales; M. Desort; S. Dieters; D. Dominis; J. Donatowicz; M. Hoffman; S. Kane; J.B. Marquette; R. Martin; P. Meintjes; K. Pollard; K. Sahu; C. Vinter; J. Wambsganss; K. Woller; K. Horne; I. Steele; D. Bramich; M. Burgdorf; C. Snodgrass; M. Bode; A. Udalski; M. Szymanski; M. Kubiak; T. Wieckowski; G. Pietrzynski; I. Soszynski; O. Szewczyk; L. Wyrzykowski; B. Paczynski (2006). “Discovery of a Cool Planet of 5.5 Earth Masses Through Gravitational Microlensing”. 《Nature》 439: 437 – 440. doi:10.1038/nature04441.
[깨진 링크([https://web.archive.org/web/*/http://news.dongascience.com/HTML/News/2009/08/21/20090821200000023463/200908212000000234630102000000.html 과거 내용 찾기)] [창의연구단공동기획]ET가 사는 곳을 찾아라], 동아사이언스, 한정호, 2009-08-21 입력, 2009-08-28 확인.
A.T. Lawton; P. Wright (1989). “A planetary system for Gamma Cephei?”. 《Journal of the British Interplanetary Society》 42: 335–336. Bibcode:1989JBIS...42..335L.
G.A.H. Walker; Bohlender, David A.; Walker, Andrew R.; Irwin, Alan W.; Yang, Stephenson L. S.; Larson, Ana (1992). “Gamma Cephei – Rotation or planetary companion?”. 《Astrophysical Journal Letters》 396 (2): L91–L94. Bibcode:1992ApJ...396L..91W. doi:10.1086/186524.
A.P. Hatzes; Cochran, William D.; Endl, Michael; McArthur, Barbara; Paulson, Diane B.; Walker, Gordon A. H.; Campbell, Bruce; Yang, Stephenson (2003). “A Planetary Companion to Gamma Cephei A”. 《Astrophysical Journal》 599 (2): 1383–1394. arXiv:astro-ph/0305110. Bibcode:2003ApJ...599.1383H. doi:10.1086/379281.
Laurence R. Doyle; Carter, J. A.; Fabrycky, D. C.; Slawson, R. W.; Howell, S. B.; Winn, J. N.; Orosz, J. A.; Pr Sa, A.; Welsh, W. F. (2011년 9월 16일). “Kepler-16: A Transiting Circumbinary Planet”. 《Science》 333 (6049): 1602–6. arXiv:1109.3432. Bibcode:2011Sci...333.1602D. doi:10.1126/science.1210923. PMID21921192.
J.P. Beaulieu; D.P. Bennett; P. Fouque; A. Williams; M. Dominik; U.G. Jorgensen; D. Kubas; A. Cassan; C. Coutures; J. Greenhill; K. Hill; J. Menzies; P.D. Sackett; M. Albrow; S. Brillant; J.A.R. Caldwell; J.J. Calitz; K.H. Cook; E. Corrales; M. Desort; S. Dieters; D. Dominis; J. Donatowicz; M. Hoffman; S. Kane; J.B. Marquette; R. Martin; P. Meintjes; K. Pollard; K. Sahu; C. Vinter; J. Wambsganss; K. Woller; K. Horne; I. Steele; D. Bramich; M. Burgdorf; C. Snodgrass; M. Bode; A. Udalski; M. Szymanski; M. Kubiak; T. Wieckowski; G. Pietrzynski; I. Soszynski; O. Szewczyk; L. Wyrzykowski; B. Paczynski (2006). “Discovery of a Cool Planet of 5.5 Earth Masses Through Gravitational Microlensing”. 《Nature》 439: 437 – 440. doi:10.1038/nature04441.
Laurence R. Doyle; Carter, J. A.; Fabrycky, D. C.; Slawson, R. W.; Howell, S. B.; Winn, J. N.; Orosz, J. A.; Pr Sa, A.; Welsh, W. F. (2011년 9월 16일). “Kepler-16: A Transiting Circumbinary Planet”. 《Science》 333 (6049): 1602–6. arXiv:1109.3432. Bibcode:2011Sci...333.1602D. doi:10.1126/science.1210923. PMID21921192.
Sigurdsson, S.; Richer, H.B.; Hansen, B.M.; Stairs I.H.; Thorsett, S.E. (2003). “A Young White Dwarf Companion to Pulsar B1620-26: Evidence for Early Planet Formation”. 《Science》 301 (5630): 193 – 196. doi:10.1126/science.1086326. PMID12855802.