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{{Starbox begin
| name=PSR B1937+21}}
{{Starbox image |
| image =
| caption = }}
{{Starbox observe
| epoch=J2000
| ra= 19 h 39 m 560210 s<ref name="astrometry1">{{cite journal | author = [[Victoria Kaspi|Kaspi, V. M.]]; Taylor, J. H.; Ryba, M. F. | title = High-precision timing of millisecond pulsars. 3: Long-term monitoring of PSRs B1855+09 and B1937+21 | journal = Astrophysical Journal | volume = 428 | pages = 713–728 | year = 1994 | url = http://adsabs.harvard.edu/abs/1994ApJ...428..713K | doi = 10.1086/174280 | accessdate = 2010-02-14 | issue = 2 | archive-date = 2017-11-20 | archive-url = https://web.archive.org/web/20171120171335/http://adsabs.harvard.edu/abs/1994ApJ...428..713K | dead-url = no }}</ref>
| dec= +21°34' 59.14166" <ref name="astrometry1"/>
| constell=[[狐狸座]]<ref name="nature_letter">{{cite journal | author = Backer, D. C.; Kulkarni, S. R.; Heiles, C.; Davis, M. M.; Goss, W. M. | title = A millisecond pulsar | journal = Nature | volume = 300 | pages = 315–318 | year = 1982 | url = http://www.nature.com/nature/journal/v300/n5893/abs/300615a0.html | doi = 10.1038/300615a0 | accessdate = 2010-02-14 | archive-date = 2010-08-02 | archive-url = https://web.archive.org/web/20100802014552/http://www.nature.com/nature/journal/v300/n5893/abs/300615a0.html | dead-url = no }}</ref>
| appmag_v = }}
{{Starbox character
| class=[[脉冲星]]
| b-v = ?
| u-b = ?
| variable =}}
{{Starbox astrometry
| radial_v=
| prop_mo_ra=-0.130<ref name="astrometry2">{{cite journal | author = Dewey, R. J.; Ojeda, M. R.; Gwinn, C. R.; Jones, D. L.; Davis, M. M. | title = VLBI Astrometry of the Millisecond Pulsar B1937+21 | journal = Astronomical Journal | volume = 111 | pages = 315–319 | year = 1996 | url = http://adsabs.harvard.edu/abs/1996AJ....111..315D | doi = 10.1086/117783 | accessdate = 2010-02-14}}</ref>
| prop_mo_dec=-0.464<ref name="astrometry2"/>
| parallax=<0.28<ref name="astrometry1"/>
| p_error=0.08
| dist_ly = >11700
| dist_pc=>3600<ref name="xray">{{cite journal | author =Nicastro, L.; Cusumano, G.; Löhmer, O.; Kramer, M.; Kuiper, L.; Hermsen, W.; Mineo, T.; Becker, W. | title = BeppoSAX observation of PSR B1937+21 | journal = Astronomy and Astrophysics | volume = 413 | pages = 1065–1072 | year = 2004 | url = http://adsabs.harvard.edu/abs/2003astro.ph.10299N | doi =10.1051/0004-6361:20031593 | accessdate = 2010-02-14}}</ref>}}
{{Starbox detail
| mass=
| radius=
| luminosity=
| temperature=
| metal=
| rotation= 1.55780648819794 [[毫秒]]<ref name="astrometry1"/>
| age=2.29{{Esp|8}}<ref name="kulkarni_overview">{{cite conference
| first = Shri
| last = Kulkarni
| authorlink = Shri Kulkarni
| coauthors =
| title = The First Decade of Millisecond Pulsars: An Overview
| booktitle = Millisecond Pulsars: A Decade of Surprise
| pages = 79–101
| publisher = Astronomical Society of the Pacific
| date = January 3–7, 1994
| location = San Francisco
| url = http://adsabs.harvard.edu/abs/1995ASPC...72...79K
| accessdate = 2010-02-14}}</ref>}}
{{Starbox catalog
| names= [[脉冲星|PSR]] B1937+214, 4C21.53, PSR J1939+213}}
{{Starbox reference
| Simbad = PSR B1937+21
}}
{{Starbox end}}

'''PSR B1937+21''' 是一颗位于[[狐狸座]]的[[脉冲星]]，离人类历史上发现的第一颗脉冲星[[PSR B1919+21]]仅有数度的距离<ref name="nature_letter"/>。PSR B1937+21的命名是根据脉冲星的命名规则而定的：PSR是脉冲星英文pulsar的缩写，1937是指该脉冲星位于[[赤经]]19 h 37 m，+21是指其位于[[赤纬]]+21°，B意味着赤经赤纬值是归算到[[分点岁差|历元1950年]]的值。PSR B1937+21是在1982年由[[美国]][[天文物理学|天文物理学家]][[唐纳德·贝克]]和他的合作者所发现的。它是人类历史上发现的第一颗[[毫秒脉冲星]]，其自转周期为1.557708[[毫秒]]，每秒自转约642圈<ref name="discovery">{{cite journal | author = Backer, D.; Kulkarni, S.; Heiles, C.; Davis, M.; Goss, M. | title = Millisecond Pulsar in 4C 21.53 | journal = IAU Circ. | volume = 3743 | year = 1982 | editor = B.G. Marsden | url = http://adsabs.harvard.edu//abs/1982IAUC.3743....2B | accessdate = 2010-02-14 | issue = 2 | archive-date = 2016-03-04 | archive-url = https://web.archive.org/web/20160304221101/http://adsabs.harvard.edu//abs/1982IAUC.3743....2B | dead-url = no }}</ref>。这颗不同寻常的毫秒脉冲星自转周期要远远小于[[天文学家]]之前估计的脉冲星自转最低极限，无法用已有的理论来解释它的特性，使得人们知道处于双星系统脉冲星可以通过[[吸积]]其伴星的物质而使自身的转速不断加快<ref name="radhakrishnan">{{cite journal | author = Radhakrishnan, V.; Srinivasan, G. | title = On the origin of the recently discovered ultra-rapid pulsar | journal = Current Science | volume = 51 | pages = 1096–1099 | year = 1982 | url = http://adsabs.harvard.edu//abs/1982CSci...51.1096R | accessdate = 2010-02-14 | archive-date = 2016-03-04 | archive-url = https://web.archive.org/web/20160304205711/http://adsabs.harvard.edu//abs/1982CSci...51.1096R | dead-url = no }}</ref>。PSR B1937+21以及之后发现的毫秒脉冲星自转周期都非常稳定（减慢的速率非常慢），可以和[[原子钟]]相媲美。PSR B1937+21有一个不寻常的特性，它是少数几颗可以偶然发射出强脉冲的脉冲星中的一颗，这是目前观察到的最明亮的无线电波。PSR B1937+21的这些特点，以及发现过程的未预见性，为脉冲星的相关研究开启了新的窗口。

==背景==
{{main|脉冲星}}
[[Image:Pulsar schematic.svg|thumb|left|脉冲星示意图]]
历史上发现的首颗[[脉冲星]][[PSR B1919+21]]是在1967年由[[剑桥大学]][[卡文迪许实验室]]的研究生[[乔丝琳·贝尔]]和她的导师[[安东尼·休伊什]]发现的<ref name="cp1919">{{cite journal | author = Hewish, A; Bell, S. J.; Pilkington, J. D. H.; Scott, P. F.; Collins, R. A. | title = Observation of a Rapidly Pulsating Radio Source | journal = [[Nature (journal)|Nature]] | volume = 217 | pages = 709–713 | date = 24 February 1968 | url = http://adsabs.harvard.edu/abs/1968Natur.217..709H | doi = 10.1038/217709a0 | accessdate = 2010-02-14 | archive-date = 2017-03-19 | archive-url = https://web.archive.org/web/20170319044531/http://adsabs.harvard.edu/abs/1968Natur.217..709H | dead-url = no }}</ref>。在脉冲星被发现后不久，[[弗朗科·帕西尼]]和[[托马斯·戈尔德]]两人独立地指出脉冲星就是快速自转的[[中子星]]，是10倍以上[[太阳质量]]的[[恒星]]死亡时发生[[II型超新星|超新星爆炸]]的产物。<ref name="pacini">{{cite journal | author = Pacini, F. | title = Rotating Neutron Stars, Pulsars and Supernova Remnants | journal = Nature | volume = 219 | issue = 5150 | pages = 145–146 | year = 1968 | url = http://adsabs.harvard.edu/abs/1968Natur.219..145P | doi = 10.1038/219145a0 | accessdate = 2010-02-14 | archive-date = 2019-04-30 | archive-url = https://web.archive.org/web/20190430054822/http://adsabs.harvard.edu/abs/1968Natur.219..145P | dead-url = no }}</ref><ref name = "gold">{{cite journal | author = Gold, T. | title = Rotating Neutron Stars as the Origin of the Pulsating Radio Sources | journal = Nature | issue = 5143 | pages = 731–732 | year = 1968 | doi = 10.1038/218731a0 | url = http://adsabs.harvard.edu//abs/1968Natur.218..731G | accessdate = 2010-02-14 | volume = 218 | archive-date = 2018-08-09 | archive-url = https://web.archive.org/web/20180809111752/http://adsabs.harvard.edu/abs/1968Natur.218..731G | dead-url = no }}</ref>。脉冲星辐射出的[[电磁波]]是由位于其周围高速旋转的磁场中的[[等离子体]]相互作用所引起。这种相互作用引起脉冲星的灯塔效应，即辐射只能沿着磁轴方向，从两个磁极区辐射出来<ref name="gold" />。由于中子星的自转轴和磁轴一般并不重合，每当射电波束扫过地球时，就接收到一个脉冲。

==发现==
20世纪70年代末，射电源4C21.53引起射电天文学家的注意，因为它具有异常高的[[行星际闪烁]]<ref name="purvis1983">{{cite journal | last = Purvis | first = Alan | title = 4C21.53 - A possible supernova remnant in Vulpecula | journal = Monthly Notices of the Royal Astronomical Society | volume = 202 | year = 1983 | pages = 605–614 | url = http://adsabs.harvard.edu/full/1983MNRAS.202..605P | accessdate = 2010-02-14}}</ref>。行星际闪烁意味着附近有致密的射电源，这表示4C21.53可能就是一个[[超新星遗迹]]<ref name="purvis1983"/>。但[[罗塞尔·赫尔斯]]和[[约瑟夫·泰勒]]在1974年利用[[阿雷西博天文台]]的射电望远镜进行巡天时曾经观测过这个天区，并没有发现和4C21.53有关的脉冲星<ref name = "hulse_taylor1974">{{cite journal | author = Hulse, R. A.; Taylor, J. H. | title = A High-Sensitivity Pulsar Survey | journal = Astrophysical Journal | volume = 191 | pages = 59–61 | url = http://adsabs.harvard.edu/abs/1974ApJ...191L..59H | doi = 10.1086/181548 | year = 1974 | accessdate = 2010-02-14}}</ref>。由于没有人能估计到脉冲星的自转周期可能短至毫秒级，因次之后的一些研究小组对这个射电源进行反复观测也始终无法找到相应的脉冲星。于是科学家提出了一系列对4C21.53出现闪烁的新解释，其中有一种解释是4C21.53可能对应一种新类型的天体<ref>{{cite journal | author = Rickard, J. J.; Cronyn, W. M. | title = Interstellar scattering, the North Polar Spur, and a possible new class of compact galactic radio sources | journal = Astrophysical Journal | volume = 228 | pages = 755–762 | url = http://adsabs.harvard.edu/abs/1979ApJ...228..755R | doi = 10.1086/156901 | accessdate = 2010-02-14|date=March 1979}}</ref>。

[[美国]][[天文物理学|天文物理学家]][[唐纳德·贝克]]和他的合作者在1982年意识到这可能和射电源隐藏的脉冲星自转速度快，超过了仪器接收和测量的敏感度有关。贝克利用阿雷西博射电望远镜和新研制的消色散能力很强的接收机，在观测时不断调整接收机的时间常数，其中包括对极短脉冲周期敏感的常数<ref name="backer_review">{{cite journal | last = Backer | first = Don | authorlink = Don Backer | title = Millisecond pulsars | journal = Journal of Astrophysics and Astronomy | volume = 5 | year = 1984 | pages = 187–207 | doi = 10.1007/BF02714539 | url = http://www.springerlink.com/content/728h54315488p017/ | accessdate = 2010-02-14 | issue = 3 }}{{Dead link|date=2020年2月 |bot=InternetArchiveBot |fix-attempted=yes }}</ref>。他们最初的计划时是先将仪器调到对转速500赫兹以下敏感的波段寻找，如果是这样的话，每秒自转642次的PSR B1937+21将不会这么快就被发现。当时贝克的学生[[史瑞·库卡尼]]简化了程序，直接采用0.4毫秒周期的波段，这样的话可以寻找到转速最快为2500赫兹的脉冲星<ref name="kulkarni_overview" />。 1982年11月，贝克宣布寻找到4C21.53对应的脉冲星，它的自转周期为1.558毫秒，远远超过天文学家之前设想的脉冲星自转极限<ref name="kulkarni_overview"/><ref name="discovery"/>。

==特征==
===年龄和自转周期减缓===
当贝克等人在1982年11月报告他们的发现时，他们指出PSR B1937+21的自转周期正在变慢，每秒钟减速3{{Esp|-14}}秒<ref name="discovery"/>。由于脉冲星靠消耗自转能而弥补辐射出去的能量，因而自转会逐渐放慢。他们使用最初观测到数据，并假定脉冲星的自转一周的极限为0.5毫秒，得出PSR B1937+21的最大年龄约为750岁<ref name="radhakrishnan" />。之所以选择0.5毫秒做为脉冲星的自转最快极限，是因为这种情况下，脉冲星旋转的[[离心力]]和其自身重力是相等的，超过这个极限，脉冲星的固体外壳就会因承受不了离心力而破碎<ref name="chakrabarty">{{cite journal | author = Chakrabarty, D.; Morgan, E. H.; Muno, M. P.; Galloway, D. K.; Wijnands, R.; van der Klis, M.; Markwardt, C. B. | title = Nuclear-powered millisecond pulsars and the maximum spin frequency of neutron stars | journal = Nature | volume = 424 | issue = 6944 | pages = 42–44 | year = 2003 | url = http://www.nature.com/nature/journal/v424/n6944/abs/nature01732.html | doi = 10.1038/nature01732 | accessdate = 2010-02-14 | pmid = 12840751 | archive-date = 2009-05-14 | archive-url = https://web.archive.org/web/20090514032642/http://www.nature.com/nature/journal/v424/n6944/abs/nature01732.html | dead-url = no }}</ref>，其具体数值取决于采用哪个[[中子星]][[状态方程 (宇宙学)|状态方程]]，不同的方程算出的脉冲星自转最快极限值不同，但都在0.3至1毫秒之间，即频率为1000-3000[[赫兹]]<ref name="gr_recycling">{{cite journal | author = Cook, G. B.; Shapiro, S. L.; Teukolsky, S. A. | title = Recycling Pulsars to Millisecond Periods in General Relativity | journal = Astrophysical Journal Letters | volume = 423 | pages = 117–120 | year = 1994 | url = http://adsabs.harvard.edu/abs/1994ApJ...423L.117C | doi = 10.1086/187250 | accessdate = 2010-02-14}}</ref><ref name="minimum_period">{{cite journal | author = Haensel, P.; Lasota, J. P.; Zdunik, J. L. | title = On the minimum period of uniformly rotating neutron stars | journal = Astronomy and Astrophysics | volume = 344 | pages = 151–153 | year = 1999 | url = http://adsabs.harvard.edu/abs/1999A&A...344..151H | accessdate = 2010-02-14}}</ref>。可能有一些机制如[[重力波 (相对论)|重力波]]等阻止脉冲星的自转到达这个极限<ref name="chakrabarty" />。

在其他[[波长|波段]]对这颗理论年龄不超过750岁的脉冲星的观测却得出矛盾的结论。这PSR B1937+21附近天区没有发现[[超新星遗迹]]，也没有明亮的[[X射线源]]<ref name="nature_letter"/>。如果PSR B1937+21的确是一个年轻的脉冲星，理应在其附近发现[[超新星]]爆发留下的痕迹。年轻的脉冲星理论上应该是非常热，如果这样的话，PSR B1937+21发出的热辐射应该会在X射线波段被观测到<ref name="radhakrishnan" />。[[文卡特拉曼·拉达克里希南]]和[[G·斯里尼瓦桑]]以观察不到超新星遗迹为依据，认为PSR B1937+21没有经历过接近理论旋转极限，而是通过吸积其伴星的物质使得自身的[[角动量]]增加，导致自身的加速，这个理论目前已经被用来解释[[毫秒脉冲星]]的形成机制。他们还提出一个理论估计这种类型脉冲星的减慢速率为每秒减慢1{{Esp|-19}}秒<ref name="radhakrishnan"/>。贝克等人在发现PSR B1937+21一个月后通过更深入的观察修正了这颗脉冲星的减慢速率，为自转周期每秒减慢1{{Esp|-15}}秒<ref name="discovery_revision">{{cite journal | author = Backer, D.; Kulkarni, S.; Heiles, C. | title = Millisecond Pulsar in 4C.53 | journal = IAU Circ. | volume = 3746 | year = 1982 | editor = B. G. Marsden | url = http://adsabs.harvard.edu/abs/1982IAUC.3746....3B | accessdate = 2010-02-14 | issue = 3}}</ref>，但后来更精确的观测值为每秒减慢1.05{{Esp|-19}}秒，十分接近拉达克里希南等人提出的理论值。目前PSR B1937+21的年龄确定为2.29{{Esp|8}}年，这个年龄和目前的观测资料相符合<ref name="kulkarni_overview"/>。

为PSR B1937+21提供加速能量的伴星现在已经不存在，这使它成为目前已经少数几颗没有拥有恒星级别质量伴星的毫秒脉冲星之一<ref name = "phillips"/>。在毫秒脉冲星旁边发现伴星的现象是可以预计到的，因为伴星是脉冲星加速至毫秒脉冲星的必要条件。但是，毫秒脉冲星无需一直从它的伴星获取物质，而只需在某个时间内进行物质吸积即可，因此现在没有伴星的PSR B1937+21不应被认为是和毫秒脉冲星加速理论相冲突。PSR B1937+21的伴星可能已经提供完所有物质而消失，或受到潮汐力作用而瓦解<ref name="solitary">{{cite journal | author = Becker, W.; Trümper, J.; Lommen, A. N.; Backer, D. C. | title = X-Rays from the Nearby Solitary Millisecond Pulsar PSR J0030+0451: The Final ROSAT Observations | journal = The Astrophysical Journal | volume = 545 | issue = 2 | pages = 1015–1019 | year = 2000 | url = http://adsabs.harvard.edu/abs/2000ApJ...545.1015B | accessdate = 2010-02-14 | doi = 10.1086/317839}}</ref>。

===脉冲===
在PSR B1937+21的一个旋转周期可以观察到两个峰值，即脉冲和中间脉冲，相距接近180°<ref name="backer_review"/>。PSR B1937+21一个比较不寻常的特性是它在一个旋转周期内偶尔可以发射出一些强度更大的脉冲。至1995年，已知拥有这种特性的脉冲星只有PSR B1937+21和[[蟹状星云脉冲星]]<ref name="giant_pulses">{{cite journal | author = Cognard, I.; Shrauner, J. A.; Taylor, J. H.; Thorsett, S. E. | title = Giant Radio Pulses from a Millisecond Pulsar | journal = Astrophysical Journal Letters | volume = 457 | pages = 81–84 | year = 1996 | url = http://adsabs.harvard.edu/abs/1996ApJ...457L..81C | doi = 10.1086/309894 | accessdate = 2010-02-14 | archive-date = 2014-06-26 | archive-url = https://web.archive.org/web/20140626035707/http://adsabs.harvard.edu/abs/1996ApJ...457L..81C | dead-url = no }}</ref>。而到2006年，在超过1500颗已知超新星中也只发现11颗超新星会发射出大强度的脉冲信号<ref name="Kusmin2007">{{cite journal | title = Giant pulses of pulsar radio emission | author = Kuzmin, A. D. | journal = Astrophysics and Space Science | volume = 308 | issue = 1–4 | pages = 563–567 | year = 2007 | doi = 10.1007/s10509-007-9347-5 | url = http://adsabs.harvard.edu/abs/2007Ap%26SS.308..563K | accessdate = 2010-03-24 | archive-date = 2017-04-05 | archive-url = https://web.archive.org/web/20170405173302/http://adsabs.harvard.edu/abs/2007Ap%26SS.308..563K | dead-url = no }}</ref>。在PSR B1937+21被发现不久，天文学家就发现它偶尔会发射大强度的脉冲，但由于受到仪器限制，再加上旋转脉冲星旋转速度快，无法观测到这些大强度脉冲单一脉冲信号，这个问题直至20世纪90年代才被解决<ref name="giant_pulses"/><ref name="backer_rad_props">{{cite journal | last = Backer | first = Don | authorlink = Don Backer | title = Millisecond pulsar radiation properties | journal = Journal of Astrophysics and Astronomy | volume = 16 | year = 1995 | pages = 165–171 | url = http://www.springerlink.com/content/02784k46ll034814/ | doi = 10.1007/BF02714831 | accessdate = 2010-02-14 | issue = 2 }}{{Dead link|date=2020年2月 |bot=InternetArchiveBot |fix-attempted=yes }}</ref>。近期对这些大强度的脉冲信号的研究发现，它们可以在脉冲和中介脉冲的后沿产生<ref name="high_brightness">{{cite journal | author = Soglasnov, V. A.; Popov, M. V.; Bartel, N.; Cannon, W.; Novikov, A. Yu.; Kondratiev, V. I.; Altunin, V. I. | title = Giant Pulses from PSR B1937+21 with Widths <=15 Nanoseconds and Tb>=5×1039 K, the Highest Brightness Temperature Observed in the Universe | journal = The Astrophysical Journal | volume = 616 | issue = 1 | pages = 439–451 | year = 2004 | url = http://adsabs.harvard.edu/abs/2004astro.ph..8285S | doi = 10.1086/424908 | accessdate = 2010-02-14}}</ref>，而且这些强脉冲的持续时间比脉冲星普通脉冲的持续时间要短，只持续10[[纳秒]]<ref name="high_brightness"/>。这些强脉冲的通量密度比较多变，最高曾发现有6.5{{e|−22}} [[瓦特|W]][[metre|m]]−2[[赫兹|Hz]]−1 （即6.5{{e|4}} Jy）<ref name="high_brightness"/>。如此高的通量密度，在加上极短的持续时间，使得PSR B1937+21的亮温度超过5{{Esp|39}} [[热力学温标|K]]，使它成为目前观测到最明亮的无线电辐射<ref name="high_brightness"/>。实际上，PSR B1937+21是目前已知最明亮的毫秒脉冲星<ref name="">{{cite journal | author = Cordes, J. M.; Chernoff, D. F. | title = Neutron Star Population Dynamics. I. Millisecond Pulsars | journal = Astrophysical Journal | volume = 482 | pages = 971–992 | year = 1997 | url =http://adsabs.harvard.edu/abs/1997astro.ph..6162C | accessdate = 2010-02-14 | doi = 10.1086/304179}}</ref>。除了在无线电波段外，PSR B1937+21在[[X射线]]波段也可以观测到脉冲信号，也探测有脉冲和中介脉冲两个脉冲峰值<ref name = "xray"/>。

== 行星系统 ==
在1990年[[亞歷山大·沃爾茲森]]发现[[PSR B1257+12]]拥有[[太阳系外行星|行星]]后，科学家重新分析PSR B1937+21等超新星的观测数据，看是否能发现类似的行星。1994年，科学家确定PSR B1937+21有一颗距离在2个[[天文单位]]以内，质量上限为地球1000倍的行星<ref name = "phillips">{{cite journal | author = Phillips, J. A.; Thorsett, S. E. | title = Planets around pulsars: A review | journal = Astrophysics and Space Science | volume = 212 | pages = 91‒106 | year = 1994| url = http://adsabs.harvard.edu/abs/1994Ap&SS.212...91P | accessdate = 2010-02-14 | issue = 1‒2 | doi = 10.1007/BF00984513}}</ref> 。1999年，沃斯赞指出PSR B1937+21发出的脉冲波周期有细微的差别，之前日本人Tokio Fukushima通过分析也相同的结论，这可能是由围绕它旋转的[[矮行星]]引起的。经过计算可知，一个类似[[谷神星]]大小的矮行星在距离这颗脉冲星2.71天文单位可引起这样的效应，但仍然需要更多的观察数据对这种假设进行验证<ref name="pulsar_planet">{{Cite journal | url=http://adsabs.harvard.edu/abs/1999ptgr.conf..101W| author=Wolszczan, A. | title=Detecting Planets Around Pulsars| journal=Pulsar Timing, General Relativity and the Internal Structure of Neutron Stars | pages=101–115 | year=1999|bibcode=1999ptgr.conf..101W | accessdate = 2010-02-14}}</ref>。

{{OrbitboxPlanet begin}}
{{OrbitboxPlanet
| exoplanet = b(未确定)
| mass_earth= 0.000158
| semimajor = 2.7
| period = 1387
}}
{{Orbitbox end}}

==重要性==
在2006年每秒自转716次的[[PSR J1748-2446ad]]被发现之前，PSR B1937+21一直保持自转最快中子星的头衔<ref name="j1748">{{cite journal | author = Hessels, J. W. T.; Ransom, S. M.; Stairs, I. H.; Freire, P. C. C.; Kaspi, V. M.; Camilo, F. | title = A Radio Pulsar Spinning at 716 Hz | journal = Science | volume = 311 | year = 2006 | pages = 1901–1904 | url = http://www.sciencemag.org/cgi/content/abstract/311/5769/1901 | doi = 10.1126/science.1123430 | pmid = 16410486 | accessdate = 2010-02-14 | issue = 5769 | archive-date = 2008-07-19 | archive-url = https://web.archive.org/web/20080719181702/http://www.sciencemag.org/cgi/content/abstract/311/5769/1901 | dead-url = no }}</ref>。直至2010年，PSR B19371+21依然是已知自转第二快的中子星<ref name="atnf_list">{{cite web | title = The ATNF Pulsar Database | url = http://www.atnf.csiro.au/research/pulsar/psrcat/proc_form.php?Name=Name&P0=P0&P1=P1&startUserDefined=true&c1_val=&c2_val=&c3_val=&c4_val=&sort_attr=p0&sort_order=asc&condition=&pulsar_names=&ephemeris=short&coords_unit=raj%2Fdecj&radius=&coords_1=&coords_2=&style=Long+with+last+digit+error&no_value=*&fsize=3&x_axis=&x_scale=linear&y_axis=&y_scale=linear&state=query&table_bottom.x=74&table_bottom.y=20 | accessdate = 2009-05-17 | archive-date = 2014-01-06 | archive-url = https://web.archive.org/web/20140106210908/http://www.atnf.csiro.au/research/pulsar/psrcat/proc_form.php?Name=Name&P0=P0&P1=P1&startUserDefined=true&c1_val=&c2_val=&c3_val=&c4_val=&sort_attr=p0&sort_order=asc&condition=&pulsar_names=&ephemeris=short&coords_unit=raj%2Fdecj&radius=&coords_1=&coords_2=&style=Long+with+last+digit+error&no_value=*&fsize=3&x_axis=&x_scale=linear&y_axis=&y_scale=linear&state=query&table_bottom.x=74&table_bottom.y=20 | dead-url = no }}</ref>。这个结果是建立在观测的敏感脉冲周期比发现PSR B1937+21时增大20倍，磁场范围增大100倍的基础上<ref name="backer_remarks">{{cite conference
| first = Don
| last = Backer
| authorlink = Don Backer
| title = Concluding Remarks
| booktitle = Millisecond Pulsars: A Decade of Surprise
| pages = 435–438
| publisher = Astronomical Society of the Pacific
| date = January 3–7, 1994
| location = San Francisco
| accessdate = 2010-02-14
| url = http://adsabs.harvard.edu/abs/1995ASPC...72..435B}}</ref>。

做为第一颗被发现的[[毫秒脉冲星]]，PSR B1937+21为探究脉冲星、中子星，甚至是解决[[重力波 (相对论)|引力波]]问题提供了新的“[[实验室]]”<ref name="encounters">{{cite journal | author = Thomsen, D. E. | title = Pulsar Encounters of a Third Kind | journal = Science News | volume = 123 | page = 4 | url = http://www.jstor.org/stable/3967824 | accessdate = 2010-02-14 | issue = 1 | date = January 1984 | archive-date = 2019-04-28 | archive-url = https://web.archive.org/web/20190428163105/https://www.jstor.org/stable/3967824 | dead-url = no }}</ref>。例如，毫秒脉冲星快速旋转所需要的高[[密度]]和[[原子核]]密度相近，通过观测可以知道在如此高密度条件下物质的活动情况<ref name="j1748"/>。最初发现PSR B1937+21时估计的高减慢率也让人疑惑，因为这意味着[[引力波天文学#引力波探测器|引力波探测器]]可以直接探测到它发出的信号，但实际上信号强度却低于探测器的敏感性。现在普遍接受的观点是每100万年PSR B1937+21的旋转周期频率改变1.5 Hz<ref name="brief_backer_review">{{cite journal | last = Backer | first = Don | authorlink = Don Backer | title = The 1.5 Millisecond Pulsar | journal = Annals of the New York Academy of Sciences | volume = 422 | pages = 180–181 | year = 1984 | url = http://www3.interscience.wiley.com/journal/119527609/abstract | doi = 10.1111/j.1749-6632.1984.tb23351.x | accessdate = 2010-02-14 | issue = Eleventh Texas Symposium on Relativistic Astrophysics | author = | archive-url = https://archive.today/20130105083556/http://www3.interscience.wiley.com/journal/119527609/abstract | archive-date = 2013-01-05 | dead-url = yes }}</ref>。这种稳定性可以和现在最好的[[原子钟]]相媲美，因此可以用来当做建立星历的一种工具<ref name="brief_backer_review"/>。

PSR B1937+21的发现促使世界各大无线电观测站对脉冲星进行广泛的调查，以寻找被遗漏的脉冲星，从而重新振兴了当时被很多人认为已经“垂死的”脉冲星天文学<ref name="kulkarni_overview" />。

==参考资料==
{{reflist}}

[[Category:毫秒脈衝星]]
[[Category:狐狸座]]
[[Category:假想行星系]]

PSR B1937+21 - 版本历史

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imported>InternetArchiveBot：补救13个来源，并将0个来源标记为失效。) #IABot (v2.0.7