NGC 6441

NGC 6441
NGC 6441
观测数据(J2000 历元)
星座	天蝎座
赤经	17h 50m 13.06s
赤纬	−37° 03′ 05.2″
距离	44 kly（13.5 kpc）
视星等 (V)	7.2
视直径(V)	9.6′
物理性质
Mass	1.6×106 M☉
金属量	−0.53 dex
估计年龄	13−13.7 Gyr
	参见：球状星团，球状星团表

NGC 6441位于南天的天蝎座，是登录在NGC天体表内的一个球状星团。它是苏格兰的天文学家詹姆士·敦洛普在1826年5月13日发现的。根据敦洛普的描述，这是一个小，但有明确界线的明亮星云，直径大约20″。这个星团位于傅说 (恒星)（天蝎座 G）东北东方5弧分^[3]，与太阳相距约44,000光年 ^[2]。

这是银河系中最大和最明亮的球状星团之一，估计质量是160万倍太阳质量。它位于银河系的核球，距离银心约13 kly（3.9 kpc）^[6]，被认为是富金属量。也就是相对之下有较多高于氦元素的金属元素丰度^[4]。相较于0.64弧分的半质量半径，星团的核心区域大约是0.11弧分。在核心区域的恒星密度暗示它的亮度密度是5.25 L_⊙ pc⁻³^[2]。星团的半光度半径是7.1 ly（2.18 pc）^[6]。

这个星团有异常大量的天琴座RR变星，在2006年时有68颗候选者，并且周期长于各自金属丰度范围的典型（星团的RRab星的平均周期是0.759天）。它也有几颗第二型造父变星，在这个星团内有不寻常的高金属量^[7]。在颜色-星等图的红巨星分支章节解释，星团中至少有两种，并可能有三种不同的星族。最亮和较高温的红群聚星族集中在星团的中心。这个集团可能是富含氦的第二族恒星^[8]。

这个星团内至少有4颗毫秒脉冲星，且其中两颗是在联星系。其中一颗是轨道离心率高达0.71的联星PSR J1750−37A^[2]。这个星团有一颗X射线爆发源，X1746-370，它有着在所有的球状团和星系中已知最长的周期^[9]。最后，这而还有一个行星状星云，JaFu 2^[10]，是在银河系内已知有行星状星云的4个球状星团之一^[3]。

参考资料

^ ^1.0 ^1.1 Goldsbury, Ryan; et al, The ACS Survey of Galactic Globular Clusters. X. New Determinations of Centers for 65 Clusters, The Astronomical Journal, December 2010, 140 (6): 1830–1837, Bibcode:2010AJ....140.1830G, arXiv:1008.2755 , doi:10.1088/0004-6256/140/6/1830.
^ ^2.0 ^2.1 ^2.2 ^2.3 ^2.4 ^2.5 Freire, Paulo C. C.; et al, Eight New Millisecond Pulsars in NGC 6440 and NGC 6441, The Astrophysical Journal, March 2008, 675 (1): 670−682, Bibcode:2008ApJ...675..670F, arXiv:0711.0925 , doi:10.1086/526338.
^ ^3.0 ^3.1 ^3.2 ^3.3 O'Meara, Stephen James, Deep-Sky Companions: Southern Gems, Cambridge University Press: 360−363, 2013 [2016-09-16], ISBN 1139851543, （原始内容存档于2016-05-03）
^ ^4.0 ^4.1 Bellini, A.; et al, The Intriguing Stellar Populations in the Globular Clusters NGC 6388 and NGC 6441, The Astrophysical Journal, March 2013, 765 (1): 27, Bibcode:2013ApJ...765...32B, arXiv:1301.2822 , doi:10.1088/0004-637X/765/1/32, 32.
^ Leaman, Ryan, Insights into Pre-enrichment of Star Clusters and Self-enrichment of Dwarf Galaxies from Their Intrinsic Metallicity Dispersions, The Astronomical Journal, December 2012, 144 (6): 13, Bibcode:2012AJ....144..183L, arXiv:1209.4648 , doi:10.1088/0004-6256/144/6/183, 183.
^ ^6.0 ^6.1 ^6.2 Mackey, A. D.; van den Bergh, Sidney, The properties of Galactic globular cluster subsystems, Monthly Notices of the Royal Astronomical Society, June 2005, 360 (2): 631−645, Bibcode:2005MNRAS.360..631M, arXiv:astro-ph/0504142 , doi:10.1111/j.1365-2966.2005.09080.x.
^ Corwin, T. Michael; et al, Image-Subtraction Photometry of Variable Stars in the Globular Clusters NGC 6388 and NGC 6441, The Astronomical Journal, September 2006, 132 (3): 1014−1022, Bibcode:2006AJ....132.1014C, arXiv:astro-ph/0605569 , doi:10.1086/505745.
^ Krogsrud, David A.; et al, The Curious Radial Distributions of Horizontal Branch Stars in NGC 6441, The Astrophysical Journal Letters, April 2013, 767 (2): 5, Bibcode:2013ApJ...767L..27K, arXiv:1304.1470 , doi:10.1088/2041-8205/767/2/L27, L27.
^ Homer, L.; et al, Optical Identification of the X-Ray Burster X1746-370 in the Globular Cluster NGC 6441, The Astronomical Journal, June 2002, 123 (6): 3255−3262, Bibcode:2002AJ....123.3255H, arXiv:astro-ph/0201550 , doi:10.1086/340470.
^ Jacoby, George H.; et al, Planetary Nebulae in the Globular Cluster PAL 6 and NGC 6441, Astronomical Journal, December 1997, 114: 2611, Bibcode:1997AJ....114.2611J, doi:10.1086/118671.

[aj140_6_1830-1] 1.0 ^1.1 Goldsbury, Ryan; et al, The ACS Survey of Galactic Globular Clusters. X. New Determinations of Centers for 65 Clusters, The Astronomical Journal, December 2010, 140 (6): 1830–1837, Bibcode:2010AJ....140.1830G, arXiv:1008.2755 , doi:10.1088/0004-6256/140/6/1830.

[apj675_1_670-2] 2.0 ^2.1 ^2.2 ^2.3 ^2.4 ^2.5 Freire, Paulo C. C.; et al, Eight New Millisecond Pulsars in NGC 6440 and NGC 6441, The Astrophysical Journal, March 2008, 675 (1): 670−682, Bibcode:2008ApJ...675..670F, arXiv:0711.0925 , doi:10.1086/526338.

[omeara2013-3] 3.0 ^3.1 ^3.2 ^3.3 O'Meara, Stephen James, Deep-Sky Companions: Southern Gems, Cambridge University Press: 360−363, 2013 [2016-09-16], ISBN 1139851543, （原始内容存档于2016-05-03）

[apj765_1_32-4] 4.0 ^4.1 Bellini, A.; et al, The Intriguing Stellar Populations in the Globular Clusters NGC 6388 and NGC 6441, The Astrophysical Journal, March 2013, 765 (1): 27, Bibcode:2013ApJ...765...32B, arXiv:1301.2822 , doi:10.1088/0004-637X/765/1/32, 32.

[aj144_6_183-5] Leaman, Ryan, Insights into Pre-enrichment of Star Clusters and Self-enrichment of Dwarf Galaxies from Their Intrinsic Metallicity Dispersions, The Astronomical Journal, December 2012, 144 (6): 13, Bibcode:2012AJ....144..183L, arXiv:1209.4648 , doi:10.1088/0004-6256/144/6/183, 183.

[mnras360_2_631-6] 6.0 ^6.1 ^6.2 Mackey, A. D.; van den Bergh, Sidney, The properties of Galactic globular cluster subsystems, Monthly Notices of the Royal Astronomical Society, June 2005, 360 (2): 631−645, Bibcode:2005MNRAS.360..631M, arXiv:astro-ph/0504142 , doi:10.1111/j.1365-2966.2005.09080.x.

[aj132_3_1014-7] Corwin, T. Michael; et al, Image-Subtraction Photometry of Variable Stars in the Globular Clusters NGC 6388 and NGC 6441, The Astronomical Journal, September 2006, 132 (3): 1014−1022, Bibcode:2006AJ....132.1014C, arXiv:astro-ph/0605569 , doi:10.1086/505745.

[ajl767_2_L27-8] Krogsrud, David A.; et al, The Curious Radial Distributions of Horizontal Branch Stars in NGC 6441, The Astrophysical Journal Letters, April 2013, 767 (2): 5, Bibcode:2013ApJ...767L..27K, arXiv:1304.1470 , doi:10.1088/2041-8205/767/2/L27, L27.

[aj123_6_3255-9] Homer, L.; et al, Optical Identification of the X-Ray Burster X1746-370 in the Globular Cluster NGC 6441, The Astronomical Journal, June 2002, 123 (6): 3255−3262, Bibcode:2002AJ....123.3255H, arXiv:astro-ph/0201550 , doi:10.1086/340470.

[aj114_2611-10] Jacoby, George H.; et al, Planetary Nebulae in the Globular Cluster PAL 6 and NGC 6441, Astronomical Journal, December 1997, 114: 2611, Bibcode:1997AJ....114.2611J, doi:10.1086/118671.

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