天球赤道座標 ：12h 15m 59.860s ，+66° 13′ 50.90″
NGC 4221 是一个位于天龙座 的透鏡狀星系 ，距离地球7590万光年[3] 約翰·赫歇爾 发现[5] [4] [6] [7]
^ 1.0 1.1 1.2 1.3 Results for object NGC 4221 (NGC 4221) . NASA/IPAC Extragalactic Database. California Institute of Technology. [2021-04-18 ] . （原始内容存档 于2022-07-05）. ^ 2.0 2.1 2.2 2.3 2.4 NGC 4221 . SIMBAD . 斯特拉斯堡天文資料中心 . [2021-04-18 ] . ^ 3.0 3.1 Crook, Aidan C.; Huchra, John P.; Martimbeau, Nathalie; Masters, Karen L.; Jarrett, Tom; Macri, Lucas M. Groups of Galaxies in the Two Micron All Sky Redshift Survey. The Astrophysical Journal. 2007, 655 (2): 790–813. Bibcode:2007ApJ...655..790C arXiv:astro-ph/0610732 doi:10.1086/510201 ^ 4.0 4.1 Fouque, P.; Gourgoulhon, E.; Chamaraux, P.; Paturel, G. Groups of galaxies within 80 Mpc. II. The catalogue of groups and group members. . Astronomy and Astrophysics Supplement Series. 1992-05-01, 93 : 211–233 [2022-07-05 ] . ISSN 0365-0138 存档 于2022-04-20）. ^ Seligman, Courtney. New General Catalogue objects: NGC 4200 - 4249 . cseligman.com. [2021-04-18 ] . （原始内容存档 于2019-02-09）. ^ Garcia, A. M. General study of group membership. II. Determination of nearby groups. . Astronomy and Astrophysics Supplement Series. 1993-07-01, 100 : 47–90 [2022-07-05 ] . ISSN 0365-0138 存档 于2022-04-15）. ^ Giuricin, Giuliano; Marinoni, Christian; Ceriani, Lorenzo; Pisani, Armando. Nearby Optical Galaxies: Selection of the Sample and Identification of Groups . The Astrophysical Journal. November 2000, 543 (1): 178–194 [2022-07-05 ] . ISSN 0004-637X doi:10.1086/317070 存档 于2021-11-05） （英语） .
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12h 15m 59.860s，+66° 13′ 50.90″
. doi:10.1086/510201.
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