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| {{starbox begin|name=Black Widow Pulsar}}
| | Hi, everybody! My name is Christi. <br>It is a little about myself: I live in Netherlands, my city of Bakel. <br>It's called often Northern or cultural capital of NB. I've married 4 years ago.<br>I have 2 children - a son (Ermelinda) and the daughter (Lolita). We all like Card collecting.<br><br>Here is my website - [http://p6.in.th/profile/jogmn Cannondale mountain bike sizing.] |
| {{starbox image|image=[[File:B1957 comp.jpg|200px]]|caption=The blue and green are optical images of the field in which the black widow pulsar is found, the green indicating the [[H-alpha]] [[bow shock]]. The red and white are secondary shock structures discovered in [[x-ray]] by the [[Chandra X-ray Observatory]].}}
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| {{Starbox observe
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| | epoch=J2000
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| | ra=19h 59m 36.77s
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| | dec= +20° 48' 15.12"
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| | appmag_v=20.4
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| | constell=[[Sagitta]]}}
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| {{Starbox character
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| | class=
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| | b-v=0
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| | u-b=
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| | variable= }}
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| {{Starbox astrometry
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| | prop_mo_ra=
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| | prop_mo_dec=
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| | dist_pc=}}
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| {{Starbox detail
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| | mass=
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| | radius=
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| | luminosity=
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| | temperature=
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| | rotation=1.667 ms
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| | period=
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| | age=}}
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| {{Starbox catalog
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| | names= [[General Catalog of Variable Stars|GVCS]] QX Sge, [[Pulsar|PSR]] J1959+2048, [[Pulsar|PSR]] B1957+20
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| }}
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| {{Starbox reference | Simbad=BLACK_WIDOW}}
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| {{Starbox end}}
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| The '''Black Widow Pulsar''' (B1957+20) is an [[eclipsing binary]] [[millisecond pulsar]] that [[orbits]] with a [[brown dwarf]] companion with a period of 9.2 hours with an eclipse duration of approximately 20 minutes. When it was discovered in 1988 it was the first eclipsing binary pulsar known.<ref>{{cite journal |pages=237–9 |doi=10.1038/333237a0 |title=A millisecond pulsar in an eclipsing binary |year=1988 |last1=Fruchter |first1=A. S. |last2=Stinebring |first2=D. R. |last3=Taylor |first3=J. H. |journal=Nature |volume=333 |issue=6170 |bibcode=1988Natur.333..237F}}</ref> The prevailing theoretical explanation for the system implied that the companion is being destroyed by the gravitational environment ([[Roche lobe]] overflow) caused by the [[neutron star]], and so the sobriquet ''[[black widow (disambiguation)|black widow]]'' was applied to the object. Subsequent to this, other objects with similar features have been discovered, and the name has been applied to the class of millisecond pulsars with an ablating companion.
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| Later observations of the object showed a [[bow shock]] in [[H-alpha]] and a smaller-in-extent shock seen in [[X-ray]]s (as observed by the [[Chandra Space Telescope]]), indicating a forward velocity of approximately a million kilometers per hour.<ref>Chandra X-Ray Observatory data for B1957+20 "[http://chandra.harvard.edu/photo/2003/b1957/]"</ref>
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| In 2010 it was estimated that the neutron star’s mass was at least <math>1.66 M_\odot</math>, and possibly as high as <math>2.4 M_\odot</math> (the latter of which, if true, would surpass [[PSR J1614–2230]] for the title of most massive neutron star yet detected, and place it within range of the [[Tolman–Oppenheimer–Volkoff limit]]).<ref>{{cite journal |doi=10.1088/0004-637X/728/2/95 |title=Evidence for a Massive Neutron Star from a Radial-Velocity Study of the Companion to the Black-Widow Pulsar Psr B1957+20 |year=2011 |last1=Van Kerkwijk |first1=M. H. |last2=Breton |first2=R. P. |last3=Kulkarni |first3=S. R. |journal=The Astrophysical Journal |volume=728 |issue=2 |pages=95 |arxiv=1009.5427 |bibcode=2011ApJ...728...95V}}</ref>
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| ==Gallery==
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| Artist impressions of the Black Widow Pulsar and its environment.
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| <center>
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| <gallery>
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| File:B1957_ill1.jpg
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| File:B1957_ill2.jpg
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| </gallery>
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| </center>
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| ==References==
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| {{Commons category|Black Widow Pulsars}}
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| {{reflist}}
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| {{Stars of Sagitta}}
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| [[Category:Sagitta (constellation)]]
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| [[Category:X-ray binaries]]
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| [[Category:Eclipsing binaries]]
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| [[Category:Millisecond pulsars]]
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| [[Category:Objects named with variable star designations|Sagittae, QX]]
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| {{astronomy-stub}}
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Hi, everybody! My name is Christi.
It is a little about myself: I live in Netherlands, my city of Bakel.
It's called often Northern or cultural capital of NB. I've married 4 years ago.
I have 2 children - a son (Ermelinda) and the daughter (Lolita). We all like Card collecting.
Here is my website - Cannondale mountain bike sizing.