/Users/andrea/_magisterarbeit/korpus/clean/testkorpus/30/file9.html NN ----------------------------------------- : What's NP New NP Site NN Map NN NASA NP Homepage NP Search NP . SENT HOME NP Science NP Special JJ Exhibit NN Satellites NNS and CC Data NP Teachers NP Corner NP Ask VV an DT Astrophysicist NN Dictionary NP Resources NP Feedback NN On IN the DT Edge NN of IN . SENT Clusters NNS of IN Galaxies NNS Most JJS galaxies NNS are VBP not RB alone RB in IN the DT vast JJ expanse NN of IN space NN , , but CC are VBP connected VVN to TO one CD or CC more JJR other JJ galaxies NNS by IN gravity NN . SENT The DT same JJ force NN that WDT holds VVZ you PP onto IN the DT Earth NN can MD keep VV many JJ individual JJ galaxies NNS bound VVN together RB . SENT Groups NNS can MD be VB small JJ , , such JJ as IN two CD galaxies NNS orbiting VVG each DT other JJ , , or CC large JJ , , like IN the DT rich JJ Coma NP cluster NN of IN thousands NNS of IN galaxies NNS extending VVG for IN more JJR than IN ten CD million CD light JJ years NNS . SENT These DT are VBP the DT largest JJS objects NNS in IN the DT known VVN Universe NN , , and CC they PP have VHP many JJ properties NNS that WDT make VVP them PP great JJ astrophysical JJ laboratories NNS . SENT For IN example NN , , clusters NNS change VVP very RB slowly RB it PP takes VVZ almost RB as RB long JJ as IN the DT age NN of IN the DT Universe NN for IN significant JJ changes NNS to TO occur VV in IN clusters NNS , , thus RB clusters NNS retain VVP an DT imprint NN of IN how WRB they PP were VBD formed VVN . SENT This DT makes VVZ them PP a DT good JJ probe NN of IN the DT history NN of IN structure NN and CC galaxy NN formation NN . SENT clusters NNS tend VVP to TO hold VV onto IN the DT gas NN in IN their PP$ systems NNS , , unlike IN galaxies NNS , , where WRB the DT gas NN is VBZ forced VVN out RP through IN supernova NN explosions NNS . SENT In IN other JJ words NNS , , clusters NNS are VBP closed JJ systems NNS . SENT By IN studying VVG the DT chemical JJ composition NN of IN clusters NNS , , it PP is VBZ possible JJ to TO get VV a DT history NN of IN nucleosynthesis NN in IN the DT Universe NN . SENT the DT force NN of IN gravity NN that WDT holds VVZ clusters NNS together RB comes VVZ mostly RB from IN dark JJ matter NN , , making VVG clusters NNS an DT excellent JJ way NN to TO study VV dark JJ matter NN in IN the DT Universe NN . SENT The DT most RBS visible JJ part NN of IN galaxy NN clusters NNS , , all RB of IN the DT stars NNS in IN all DT of IN the DT galaxies NNS that WDT make VVP up RP the DT cluster NN , , is VBZ a DT small JJ fraction NN of IN the DT sum NN total NN of IN what WP makes VVZ up RP the DT cluster NN , , and CC is VBZ probably RB the DT least JJS interesting JJ part NN of IN the DT cluster NN . SENT For IN example NN , , scientists NNS from IN the DT LHEA NP study NN the DT X NP ray NN emission NN from IN galaxy NN clusters NNS . SENT The DT X NP rays NNS come VVP from IN hot JJ 10 CD 100 CD million CD degrees NNS gas NN trapped VVN by IN the DT gravitational JJ force NN of IN the DT cluster NN . SENT This DT gas NN makes VVZ up RP a DT much RB larger JJR part NN of IN the DT total JJ mass NN of IN the DT cluster NN than IN the DT stars NNS , , but CC is VBZ completely RB invisible JJ to TO human JJ eyes NNS . SENT The DT scientists NNS at IN Goddard NP Space NP Flight NP Center NP are VBP studying VVG many JJ different JJ things NNS about IN galaxy NN clusters NNS , , but CC these DT can MD be VB divided VVN into IN two CD main JJ groups NNS . SENT What WP are VBP the DT clusters NNS made VVN of IN . SENT How WRB do VVP clusters NNS evolve VV . SENT Tell VV me PP more JJR about IN Clusters NNS of IN Galaxies NNS and CC the DT scientists NNS who WP research VV them PP . SENT Home RB Imagine VV Science NP Special JJ Exhibit NN Satellites NNS and CC Data NP Dictionary NP Resources NPS Teacher's NP Corner NP Feedback NN Ask VVP an DT Astrophysicist NN Imagine VV the DT Universe NN is VBZ a DT service NN of IN the DT High NP Energy NP Astrophysics NN Science NP Archive NP Research NP Center NP HEASARC NP , , Dr NP . SENT Nicholas NP White NP Director NP , , within IN the DT Exploration NN of IN the DT Universe NN Division NP EUD NP at IN NASA's NP Goddard NP Space NP Flight NP Center NP . SENT The DT Imagine VVP Team NP Project NP Leader NP . SENT Dr NP . SENT Jim NP Lochner NP Curator NN . SENT Meredith NP Bene NP Responsible JJ NASA NP Official NP . SENT Phil NP Newman NP All DT material NN on IN this DT site NN has VHZ been VBN created VVN and CC updated VVN between IN 1997 CD 2005 CD . SENT Useful JJ plugins NNS NASA's NP privacy NN statement NN Do VVP you PP have VHP a DT question NN , , problem NN or CC comment NN about IN this DT web NN site NN . SENT Please UH let VV us PP know VV . SENT External JJ links NNS contain VVP material NN that IN we PP found VVD to TO be VB relevant JJ . SENT However RB they're NN not RB maintained VVD by IN us PP and CC the DT content NN may MD have VH changed VVN . SENT If IN you PP find VVP any DT external JJ links NNS that WDT contain VVP inappropriate JJ material NN , , please VV let VV us PP know VV . SENT