{"id":34657,"date":"2019-06-11T03:30:12","date_gmt":"2019-06-11T00:30:12","guid":{"rendered":"https:\/\/bilimvegelecek.com.tr\/?p=34657"},"modified":"2019-06-15T10:35:49","modified_gmt":"2019-06-15T07:35:49","slug":"yildizlar-nasil-olur","status":"publish","type":"post","link":"https:\/\/bilimvegelecek.com.tr\/index.php\/2019\/06\/11\/yildizlar-nasil-olur","title":{"rendered":"Y\u0131ld\u0131zlar nas\u0131l \u00f6l\u00fcr?"},"content":{"rendered":"

Sekiz G\u00fcne\u015f k\u00fctlesinden k\u00fc\u00e7\u00fck y\u0131ld\u0131zlar \u201ck\u00fc\u00e7\u00fck y\u0131ld\u0131z\u201d \u00f6tekiler de \u201cb\u00fcy\u00fck y\u0131ld\u0131z\u201d olarak tan\u0131mlan\u0131r. K\u00fc\u00e7\u00fck k\u00fctleli y\u0131ld\u0131zlarda merkezdeki yak\u0131t yani hidrojen t\u00fckenince helyum \u201cyak\u0131lmaya\u201d ba\u015flan\u0131r. Bu andan itibaren y\u0131ld\u0131z bir ana kol y\u0131ld\u0131z\u0131 olmaktan \u00e7\u0131kar. Art\u0131k \u00f6mr\u00fcn\u00fcn son a\u015famas\u0131na gelmi\u015ftir. Bu yeni s\u00fcre\u00e7te merkezde \u00fcretilen enerji ve olu\u015fan bas\u0131n\u00e7, y\u0131ld\u0131z\u0131n i\u00e7ine \u00e7\u00f6kmesi i\u00e7in \u00e7al\u0131\u015fan k\u00fctle\u00e7ekim kuvvetini dengelemenin \u00f6tesine ge\u00e7er. Bunun sonucunda merkezden uzak b\u00f6lgelerde (zay\u0131f bir k\u00fctle\u00e7ekimle y\u0131ld\u0131za ba\u011fl\u0131 olan) maddeler h\u0131zla uzaya do\u011fru geni\u015flemeye ba\u015flar. Y\u0131ld\u0131z sanki ikiye b\u00f6l\u00fcnm\u00fc\u015f gibidir: Merkezde \u0131\u015f\u0131yan ve k\u00fc\u00e7\u00fclen \u201c\u00e7ekirdek\u201d ve uzaya do\u011fru giderek geni\u015fleyen \u00fcst katmanlar vard\u0131r. Y\u0131ld\u0131z bir dizi a\u015famadan ge\u00e7tikten sonra bir \u201ck\u0131rm\u0131z\u0131 dev\u201d olur; \u00f6ylesine b\u00fcy\u00fcr ki yar\u0131\u00e7ap\u0131 2-3 AB kadar olabilir. Bu h\u0131zl\u0131 geni\u015fleme s\u00fcrer ve zamanla y\u0131ld\u0131z\u0131n d\u0131\u015f katmanlar\u0131 uzaya yay\u0131l\u0131r. Y\u0131ld\u0131z\u0131n art\u0131k geri d\u00f6n\u00fc\u015f\u00fc olmayan bir \u015fekilde uzaya yay\u0131lan b\u00f6l\u00fcm\u00fcne \u201cgezegenimsi bulutsu\u201d denir.Bu s\u0131rada y\u0131ld\u0131z\u0131n \u00e7ekirde\u011fi de bir s\u00fcre daha i\u00e7ine \u00e7\u00f6ker. Merkezin i\u00e7ine \u00e7\u00f6k\u00fc\u015f\u00fc sona erdi\u011finde geriye \u00e7ok k\u00fc\u00e7\u00fck ama \u00e7ok da yo\u011fun -\u00f6rne\u011fin G\u00fcne\u015f k\u00fctlesinde ama D\u00fcnya b\u00fcy\u00fckl\u00fc\u011f\u00fcnde- bir y\u0131ld\u0131z kal\u0131r. Bu t\u00fcr y\u0131ld\u0131zlara beyaz c\u00fcce denir. Beyaz c\u00fccelerin k\u00fctlesi 0,2-1,3 G\u00fcne\u015f k\u00fctlesi aras\u0131nda olur. B\u00f6ylesi b\u00fcy\u00fck bir k\u00fctlenin D\u00fcnya kadar k\u00fc\u00e7\u00fck bir hacme s\u0131\u011fmas\u0131 nedeniyle beyaz c\u00fccelerin yo\u011funluklar\u0131 \u00e7ok \u00e7ok y\u00fcksektir -1 ton\/cm3<\/sup> kadar yani suyun bir milyon kat\u0131. Samanyolu\u2019ndaki y\u0131ld\u0131zlar\u0131n %95\u2019i k\u00fc\u00e7\u00fck y\u0131ld\u0131zlard\u0131r ve sonunda birer beyaz c\u00fcce olacaklard\u0131r. Beyaz c\u00fccelerin kendi enerji kaynaklar\u0131 olmad\u0131\u011f\u0131ndan y\u00fczey s\u0131cakl\u0131klar\u0131 ve parlakl\u0131klar\u0131 zamanla azal\u0131r ve renkleri de\u011fi\u015fir. Bunlar emekliye ayr\u0131lm\u0131\u015f y\u0131ld\u0131zlar gibidir. Art\u0131k etkin de\u011fillerdir. Sahip olduklar\u0131 enerjiyi uzaya yayarlar. Bu enerji de giderek azal\u0131r ve beyaz c\u00fcceler milyarlarca y\u0131l i\u00e7inde karar\u0131r. G\u00fcne\u015f\u2019e en yak\u0131n 100 y\u0131ld\u0131zdan sekizi beyaz c\u00fccedir.<\/p>\n

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Yakla\u015f\u0131k 150 \u0131\u015f\u0131k y\u0131l\u0131 \u00f6temizdeki beyaz c\u00fcce IK Pegasi B (solda) ile G\u00fcne\u015f\u2019in (sa\u011fda) b\u00fcy\u00fckl\u00fcklerinin kar\u015f\u0131la\u015ft\u0131r\u0131lmas\u0131 g\u00f6r\u00fcl\u00fcyor.<\/figcaption><\/figure>\n

B\u00fcy\u00fck k\u00fctleli y\u0131ld\u0131zlar\u0131n sonu, k\u00fc\u00e7\u00fcklere g\u00f6re olduk\u00e7a farkl\u0131 ve \u015fiddetli olur. En b\u00fcy\u00fck ana kol y\u0131ld\u0131zlar\u0131 yakla\u015f\u0131k 100 G\u00fcne\u015f k\u00fctlesindedir. B\u00f6yle y\u0131ld\u0131zlarda y\u0131ld\u0131z\u0131 olu\u015fturan maddeyi y\u0131ld\u0131z\u0131n merkezine do\u011fru \u00e7eken k\u00fctle\u00e7ekim kuvveti de b\u00fcy\u00fckt\u00fcr. Dolay\u0131s\u0131yla y\u0131ld\u0131z\u0131n merkezindeki s\u0131cakl\u0131k ve bas\u0131n\u00e7 da daha b\u00fcy\u00fck olur ve n\u00fckleer tepkimeler daha h\u0131zl\u0131 ger\u00e7ekle\u015fir. Yani daha \u00e7ok hidrojen, helyuma d\u00f6n\u00fc\u015f\u00fcr ve daha \u00e7ok enerji ortaya \u00e7\u0131kar. Bunun sonucunda merkezden d\u0131\u015fa do\u011fru olan bas\u0131n\u00e7 da daha b\u00fcy\u00fck olur. Y\u0131ld\u0131z daha b\u00fcy\u00fck bir k\u00fctle\u00e7ekim kuvvetiyle ona kar\u015f\u0131 koyan daha b\u00fcy\u00fck bir bas\u0131nc\u0131n dengesindedir. Ancak bu durumu sa\u011flamak ve s\u00fcrd\u00fcrmek i\u00e7in merkezde daha \u00e7ok madde d\u00f6n\u00fc\u015ft\u00fcr\u00fcl\u00fcr, bir anlamda \u201cyak\u0131t\u201d daha h\u0131zl\u0131 t\u00fcketilir. Bu t\u00fcr b\u00fcy\u00fck k\u00fctleli y\u0131ld\u0131zlar\u0131n y\u00fczey s\u0131cakl\u0131klar\u0131 y\u00fcksek ve parlakl\u0131klar\u0131 b\u00fcy\u00fck olur ama \u00e7ok h\u0131zl\u0131 da yak\u0131t t\u00fckettiklerinden \u00f6m\u00fcrleri k\u0131sad\u0131r. G\u00fcne\u015f\u2019ten on kat daha k\u00fctleli bir y\u0131ld\u0131z\u0131n \u00f6mr\u00fc G\u00fcne\u015f\u2019inkinin neredeyse binde biri kadard\u0131r.<\/p>\n

Bunlarda merkezdeki yak\u0131t t\u00fckenince yeni elementlerin yak\u0131t olarak kullan\u0131lmas\u0131 s\u00fcreci ba\u015flar ve bu s\u00fcre\u00e7 demire kadar devam eder. Merkezde demirden bir \u00e7ekirdek olu\u015ftuktan sonra s\u00fcre\u00e7 durur. Y\u0131ld\u0131z\u0131 hidrostatik dengede tutan g\u00fc\u00e7 son kez kesilince merkez h\u0131zla kendi i\u00e7ine \u00e7\u00f6kmeye ba\u015flar. K\u0131sa s\u00fcren bu a\u015faman\u0131n sonunda y\u0131ld\u0131z s\u00fcpernova denen korkun\u00e7 bir patlamayla i\u00e7eri\u011finin b\u00fcy\u00fck b\u00f6l\u00fcm\u00fcn\u00fc uzaya sa\u00e7ar. Bu patlama s\u0131ras\u0131nda patlaman\u0131n enerjisiyle demirden daha a\u011f\u0131r elementler olu\u015fur ve uzaya yay\u0131l\u0131r. Patlamada yay\u0131lan \u0131\u015f\u0131k bir g\u00f6kadan\u0131n yayd\u0131\u011f\u0131 \u0131\u015f\u0131\u011fa yak\u0131nd\u0131r. Asl\u0131nda bir s\u00fcpernovada uzaya yay\u0131lan enerjinin ancak on binde biri g\u00f6r\u00fcn\u00fcr \u0131\u015f\u0131k \u015feklinde olur.<\/p>\n

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Bir beyaz c\u00fcce, bir n\u00f6tron y\u0131ld\u0131z\u0131 ve D\u00fcnya\u2019n\u0131n b\u00fcy\u00fckl\u00fck kar\u015f\u0131la\u015ft\u0131rmas\u0131.<\/figcaption><\/figure>\n

E\u011fer y\u0131ld\u0131z\u0131n ilk k\u00fctlesi 8-20 G\u00fcne\u015f k\u00fctlesi aras\u0131ndaysa, s\u00fcpernovadan sonra merkezdeki \u00e7ekirdekten geriye \u00e7ok \u00e7ok k\u00fc\u00e7\u00fck bir y\u0131ld\u0131z kal\u0131r. Bu s\u0131ra d\u0131\u015f\u0131 y\u0131ld\u0131z\u0131n neredeyse b\u00fct\u00fcn k\u00fctlesi n\u00f6tronlardan olu\u015ftu\u011fu i\u00e7in buna n\u00f6tron y\u0131ld\u0131z\u0131 denir. Bunlar ger\u00e7ekte y\u0131ld\u0131z de\u011fildir. Kendi ekseninde \u00e7ok h\u0131zl\u0131 -saniyede onlarca kez- d\u00f6nen n\u00f6tron y\u0131ld\u0131zlar\u0131 beyaz c\u00fccelerden de yo\u011fun g\u00f6kcisimleridir. A\u015f\u0131r\u0131 s\u0131cak ve a\u015f\u0131r\u0131 derecede de manyetiktirler. Tipik bir n\u00f6tron y\u0131ld\u0131z\u0131n\u0131n k\u00fctlesi 1,3-2 G\u00fcne\u015f k\u00fctlesi aras\u0131nda olur. \u00c7ap\u0131 da yaln\u0131zca 12 km kadard\u0131r. N\u00f6tron y\u0131ld\u0131zlar\u0131n\u0131n yo\u011funluklar\u0131 1020 ton\/cm3<\/sup> d\u00fczeyindedir.<\/p>\n

E\u011fer \u00f6lmekte olan y\u0131ld\u0131z\u0131n ilk k\u00fctlesi 20 G\u00fcne\u015f k\u00fctlesinden daha b\u00fcy\u00fckse, bu kez s\u00fcpernova s\u0131ras\u0131nda merkezdeki \u00e7ekirdek n\u00f6tron y\u0131ld\u0131z\u0131na d\u00f6n\u00fc\u015fmez. Yo\u011funlu\u011fu \u00e7ok daha y\u00fcksek bir g\u00f6kcismi ortaya \u00e7\u0131kar: Karadelik.<\/p>\n

Kaynak:<\/strong> \u00c7a\u011flar Sunay,\u00a050 Soruda Evren<\/em>, Bilim ve Gelecek Kitapl\u0131\u011f\u0131, \u0130stanbul, 2011, ss. 176-180<\/p>\n","protected":false},"excerpt":{"rendered":"

Sekiz G\u00fcne\u015f k\u00fctlesinden k\u00fc\u00e7\u00fck y\u0131ld\u0131zlar \u201ck\u00fc\u00e7\u00fck y\u0131ld\u0131z\u201d \u00f6tekiler de \u201cb\u00fcy\u00fck y\u0131ld\u0131z\u201d olarak tan\u0131mlan\u0131r. K\u00fc\u00e7\u00fck k\u00fctleli y\u0131ld\u0131zlarda merkezdeki yak\u0131t yani hidrojen t\u00fckenince helyum \u201cyak\u0131lmaya\u201d ba\u015flan\u0131r. Bu andan itibaren y\u0131ld\u0131z bir ana kol y\u0131ld\u0131z\u0131 olmaktan \u00e7\u0131kar. Art\u0131k \u00f6mr\u00fcn\u00fcn son a\u015famas\u0131na gelmi\u015ftir. Bu yeni s\u00fcre\u00e7te merkezde \u00fcretilen enerji ve olu\u015fan bas\u0131n\u00e7, y\u0131ld\u0131z\u0131n i\u00e7ine \u00e7\u00f6kmesi i\u00e7in \u00e7al\u0131\u015fan k\u00fctle\u00e7ekim kuvvetini […]<\/p>\n","protected":false},"author":429,"featured_media":34658,"comment_status":"closed","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"_acf_changed":false,"footnotes":""},"categories":[3624],"tags":[657,291,2000,795,1161,404],"class_list":["post-34657","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-sorularla-bilim","tag-evren","tag-galaksiler","tag-gokbilim","tag-gunes","tag-kutlecekim","tag-yildizlar"],"acf":[],"aioseo_notices":[],"aioseo_head":"\n\t\t\n\t\n\t\n\t\n\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t