{"id":21232,"date":"2015-06-01T12:49:46","date_gmt":"2015-06-01T09:49:46","guid":{"rendered":"https:\/\/bilimvegelecek.com.tr\/?p=21232"},"modified":"2018-03-08T13:04:11","modified_gmt":"2018-03-08T10:04:11","slug":"evrende-mesafeler-nasil-olculur","status":"publish","type":"post","link":"https:\/\/bilimvegelecek.com.tr\/index.php\/2015\/06\/01\/evrende-mesafeler-nasil-olculur","title":{"rendered":"Evrende mesafeler nas\u0131l \u00f6l\u00e7\u00fcl\u00fcr?"},"content":{"rendered":"

Mesafe \u00f6l\u00e7\u00fcmleri g\u00fcnl\u00fck hayatta al\u0131\u015f\u0131k oldu\u011fumuz boyutlarda kolayd\u0131r; bir masan\u0131n uzunlu\u011funu basit bir cetvel kullanarak rahatl\u0131kla \u00f6l\u00e7ebiliriz. Ancak mesafeler k\u00fc\u00e7\u00fcld\u00fck\u00e7e veya b\u00fcy\u00fcd\u00fck\u00e7e, elimizdeki cetvellerin hassasiyeti yetersiz olmaya ba\u015flar. G\u00fcne\u015f\u2019in D\u00fcnya\u2019ya olan uzakl\u0131\u011f\u0131n\u0131 hi\u00e7bir cetvelle \u00f6l\u00e7emeyiz. Yap\u0131lmas\u0131 gereken, fizik yasalar\u0131n\u0131 kullanarak elde edilmi\u015f yeni bir astronomik cetvel icat etmektir. Ancak bu astronomik cetvel de daha uzak mesafeler i\u00e7in yeteri kadar hassas olmayabilir… \u015eansl\u0131y\u0131z ki, fizik\u00e7i ve astronomlar farkl\u0131 \u00f6l\u00e7me teknikleri geli\u015ftirerek \u00e7ok uzaktaki nesnelerin bile uzakl\u0131\u011f\u0131n\u0131 bulabilmektedir.<\/em><\/p>\n

Olgular\u0131 bilimsel \u00e7er\u00e7eveye oturtup genel a\u00e7\u0131klama bi\u00e7imleri ortaya koyabilmenin yolu g\u00f6zlem yapmaktan ge\u00e7er. Bilimin amac\u0131, eski g\u00f6zlemlerle uyumlu, olas\u0131 yeni g\u00f6zlemleri a\u00e7\u0131klama yetisine sahip teoriler geli\u015ftirmektir. G\u00f6zlem yapman\u0131n zorunlulu\u011fu da, ihtiya\u00e7 duyulan niceliksel \u00f6zelliklerin \u00f6l\u00e7\u00fcmlerindeki hassasiyeti \u00f6nemli k\u0131lar. Deney ve g\u00f6zlemsel \u00f6l\u00e7\u00fcmlerdeki hassasiyet, daha do\u011fru sonu\u00e7lar elde etmeyi sa\u011flay\u0131p, halihaz\u0131rda olan teorilerin do\u011frulu\u011funu, eksikli\u011fini veya yanl\u0131\u015fl\u0131\u011f\u0131n\u0131 ortaya \u00e7\u0131kar\u0131r.<\/p>\n

Konum, incelenmek istenen fiziksel nesneler i\u00e7in \u00f6nemli bir parametredir. Nesnelerin bir\u00e7ok fiziksel \u00f6zelli\u011fi, g\u00f6zlem yap\u0131lan nokta ile nesne aras\u0131ndaki mesafeyle do\u011frudan ili\u015fkilidir. Bu durumda mesafe \u00f6l\u00e7\u00fcmleri \u00f6zellikle fizik bilimi a\u00e7\u0131s\u0131ndan son derece \u00f6nemlidir.<\/p>\n

Mesafe \u00f6l\u00e7\u00fcmleri g\u00fcnl\u00fck hayatta al\u0131\u015f\u0131k oldu\u011fumuz boyutlarda kolayd\u0131r; bir masan\u0131n uzunlu\u011funu basit bir cetvel kullanarak rahatl\u0131kla \u00f6l\u00e7ebiliriz. Ancak mesafeler k\u00fc\u00e7\u00fcld\u00fck\u00e7e veya b\u00fcy\u00fcd\u00fck\u00e7e elimizdeki cetvellerin hassasiyeti yetersiz olmaya ba\u015flar. G\u00fcne\u015f\u2019in D\u00fcnya\u2019ya olan uzakl\u0131\u011f\u0131n\u0131 hi\u00e7bir cetvelle \u00f6l\u00e7emeyiz. Yap\u0131lmas\u0131 gereken, fizik yasalar\u0131n\u0131 kullanarak elde edilmi\u015f yeni bir astronomik cetvel icat etmektir. Ancak bu astronomik cetvel de daha uzak mesafeler i\u00e7in yeteri kadar hassas olmayabilir… \u015eansl\u0131y\u0131z ki, fizik\u00e7i ve astronomlar farkl\u0131 \u00f6l\u00e7me teknikleri geli\u015ftirerek \u00e7ok uzaktaki nesnelerin bile uzakl\u0131\u011f\u0131n\u0131 bulabilmektedir.<\/p>\n

Evrende mesafe \u00f6l\u00e7\u00fcmleri; G\u00fcne\u015f Sistemi, yak\u0131n y\u0131ld\u0131zlar, Samanyolu ve yak\u0131n galaksiler, di\u011fer galaksiler ve \u00e7ok uzaktaki nesneler i\u00e7in olmak \u00fczere 5 ba\u015fl\u0131k alt\u0131nda toplanabilir.<\/p>\n

\"\"<\/p>\n

G\u00fcne\u015f Sistemi\u2019ndeki mesafe \u00f6l\u00e7\u00fcmleri<\/strong><\/p>\n

G\u00fcne\u015f Sistemi astronomik a\u00e7\u0131dan bak\u0131ld\u0131\u011f\u0131nda \u00e7ok k\u00fc\u00e7\u00fck boyuttad\u0131r. Buradaki mesafe \u00f6l\u00e7\u00fcmleri, radar tekni\u011fi ile \u0131\u015f\u0131\u011f\u0131n yans\u0131ma \u00f6zelli\u011finden yararlan\u0131larak yap\u0131labilir: \u00d6ncelikle uzakl\u0131\u011f\u0131 \u00f6l\u00e7\u00fclmek istenen objeye \u0131\u015f\u0131k dalgas\u0131 g\u00f6nderilir. G\u00f6nderilen \u0131\u015f\u0131k nesnenin \u00fczerine \u00e7arpar; bir k\u0131sm\u0131 D\u00fcnya\u2019ya geri yans\u0131r ve b\u00f6ylece yans\u0131yan \u0131\u015f\u0131k, \u00f6l\u00e7\u00fclmek istenen mesafeyi iki kez seyahat etmi\u015f olur. Seyahat s\u00fcresi kay\u0131t edilip \u0131\u015f\u0131\u011f\u0131n uzaydaki h\u0131z\u0131n\u0131n saniyede yakla\u015f\u0131k 300.000 kilometre oldu\u011fu g\u00f6z \u00f6n\u00fcne al\u0131nd\u0131\u011f\u0131nda G\u00fcne\u015f Sistemi\u2019ndeki nesnelerin D\u00fcnya\u2019ya olan uzakl\u0131\u011f\u0131 hesaplanabilir.<\/p>\n

Yak\u0131n y\u0131ld\u0131zlar\u0131n mesafe \u00f6l\u00e7\u00fcmleri<\/strong><\/p>\n

G\u00fcne\u015f\u2019ten sonra D\u00fcnya\u2019ya en yak\u0131n y\u0131ld\u0131z olan Proxima Centauri\u2019nin uzakl\u0131\u011f\u0131 4,2 \u0131\u015f\u0131k y\u0131l\u0131d\u0131r. Yani Proxima Centauri\u2019den gelen \u0131\u015f\u0131k D\u00fcnya\u2019ya 4,2 y\u0131lda ula\u015f\u0131r. E\u011fer radar y\u00f6ntemi ile o civardaki nesnelerin uzakl\u0131\u011f\u0131n\u0131 bulmak isteseydik 8,4 \u0131\u015f\u0131k y\u0131l\u0131 beklememiz gerekirdi. Bunun yan\u0131 s\u0131ra bu denli uzak mesafelere \u0131\u015f\u0131k g\u00f6nderip, g\u00f6nderilen \u0131\u015f\u0131\u011f\u0131n D\u00fcnya\u2019ya geri yans\u0131mas\u0131n\u0131 beklemek olduk\u00e7a anlams\u0131z bir \u00e7aba olacakt\u0131r. Bu sebepler g\u00f6z \u00f6n\u00fcne al\u0131nd\u0131\u011f\u0131nda ba\u015fka bir \u00f6l\u00e7\u00fcm y\u00f6nteminin gereklili\u011fi a\u015fik\u00e2rd\u0131r. Fizik ve geometrinin i\u015fbirli\u011fiyle, 100 \u0131\u015f\u0131k y\u0131l\u0131ndan daha yak\u0131ndaki y\u0131ld\u0131zlar i\u00e7in do\u011fru sonu\u00e7lar veren paralaks y\u00f6ntemi bu gereklili\u011fi kar\u015f\u0131lar.<\/p>\n

\"\"
Paralaktik kayma: G\u00fcne\u015f\u2019e g\u00f6re iki z\u0131t noktadan \u00f6l\u00e7\u00fclen a\u00e7\u0131 de\u011fi\u015fikli\u011fi kullan\u0131larak yak\u0131n y\u0131ld\u0131zlar\u0131n uzakl\u0131\u011f\u0131 tayin edilebilir. D\u00fcnya\u2019n\u0131n G\u00fcne\u015f\u2019e ortalama uzakl\u0131\u011f\u0131 1 AB (astronomik birim) olarak adland\u0131r\u0131l\u0131r.(2)<\/figcaption><\/figure>\n

Uzakta bulunan bir cisme parma\u011f\u0131m\u0131z\u0131 hizalay\u0131p \u00f6nce sol, sonra sa\u011f g\u00f6zle bakt\u0131\u011f\u0131m\u0131zda, parma\u011f\u0131m\u0131z\u0131n uzaktaki cisme nazaran konum de\u011fi\u015ftirdi\u011fini g\u00f6r\u00fcr\u00fcz ve bu konum de\u011fi\u015fikli\u011fi parmak g\u00f6zlere yakla\u015ft\u0131k\u00e7a artar. Uzaktaki cisim referans al\u0131nd\u0131\u011f\u0131nda, bu konum de\u011fi\u015fikli\u011fi ile parma\u011f\u0131m\u0131z\u0131n g\u00f6zlerimize olan uzakl\u0131\u011f\u0131 aras\u0131nda trigonometrik bir ili\u015fki s\u00f6z konusudur. Cisimlerin uzakl\u0131klar\u0131na ba\u011fl\u0131 bu a\u00e7\u0131 de\u011fi\u015fimleri, yak\u0131n y\u0131ld\u0131zlar i\u00e7in uzakl\u0131k \u00f6l\u00e7\u00fcmlerini olanakl\u0131 k\u0131lar.<\/p>\n

Paralaks ad\u0131 verilen bu \u00f6l\u00e7\u00fcm metodunda fon y\u0131ld\u0131zlar\u0131 olarak adland\u0131r\u0131lan a\u00e7\u0131 de\u011fi\u015fiminden etkilenmeyecek denli uzak y\u0131ld\u0131zlar referans al\u0131narak, uzakl\u0131\u011f\u0131 hesaplanmak istenen yak\u0131n y\u0131ld\u0131z\u0131n ilk konumu i\u015faretlenir. D\u00fcnya, G\u00fcne\u015f etraf\u0131ndaki d\u00f6n\u00fc\u015f\u00fcn\u00fc 12 ayda tamamlad\u0131\u011f\u0131ndan, ilk \u00f6l\u00e7\u00fcmden 6 ay sonra bulundu\u011fu yerin G\u00fcne\u015f\u2019e g\u00f6re tam z\u0131t konumuna gelir. Buradan yine fon y\u0131ld\u0131zlar\u0131 referans al\u0131narak y\u0131ld\u0131z\u0131n yeni konumu i\u015faretlenir. Son olarak iki konum aras\u0131ndaki paralaks a\u00e7\u0131s\u0131 kullan\u0131larak da y\u0131ld\u0131z\u0131n uzakl\u0131\u011f\u0131 tayin edilir. Paralaks a\u00e7\u0131s\u0131 k\u00fc\u00e7\u00fck oldu\u011fundan birimi genellikle yay saniyesi olarak verilir ve y\u0131ld\u0131zlar\u0131n uzakl\u0131\u011f\u0131 artt\u0131k\u00e7a bu a\u00e7\u0131 giderek k\u00fc\u00e7\u00fcl\u00fcr. Paralaks de\u011ferleri 0,02 yay saniyesine yakla\u015ft\u0131\u011f\u0131nda, \u00f6l\u00e7\u00fcm hatalar\u0131 ortaya \u00e7\u0131kmaya ba\u015flar ve y\u00f6ntem g\u00fcvenilirli\u011fini yitirir. Ancak yeni teknoloji uydularla yap\u0131lan paralaks \u00f6l\u00e7\u00fcmleri, 100 \u0131\u015f\u0131k y\u0131l\u0131ndan \u00e7ok daha uzaktaki y\u0131ld\u0131zlar\u0131 da g\u00f6zlemleyebilme kapasitesine sahiptir.<\/p>\n

1989 ve 1993 y\u0131llar\u0131 aras\u0131nda faaliyet g\u00f6steren Avrupa Uzay Ajans\u0131\u2019n\u0131n f\u0131rlatt\u0131\u011f\u0131 Hiperkus adl\u0131 uydu, 1600 \u0131\u015f\u0131k y\u0131l\u0131 uzakl\u0131kta, 118.000\u2019den fazla y\u0131ld\u0131z\u0131n uzakl\u0131\u011f\u0131n\u0131 paralaks y\u00f6ntemiyle bulmu\u015f ve kataloglam\u0131\u015ft\u0131r. Yine Avrupa Uzay Ajans\u0131 taraf\u0131ndan 2013 y\u0131l\u0131nda g\u00f6revlendirilen Gaia uydusu da yay saniyesinin y\u00fcz binde birindeki hassasl\u0131klara inerek, on binlerce \u0131\u015f\u0131k y\u0131l\u0131 uzaktaki y\u0131ld\u0131zlar\u0131 g\u00f6zlemlemeye devam etmektedir.<\/p>\n

\"\"
Evrende baz\u0131 mesafeler ve mesafeye ba\u011fl\u0131 olarak kullan\u0131lan y\u00f6ntemler.(8)<\/figcaption><\/figure>\n

Samanyolu ve yak\u0131n galaksilerde mesafe \u00f6l\u00e7\u00fcmleri<\/strong><\/p>\n

Paralaks a\u00e7\u0131lar\u0131 k\u00fc\u00e7\u00fcld\u00fck\u00e7e hatalar\u0131n artmas\u0131, paralaks y\u00f6ntemini belli bir uzakl\u0131kla s\u0131n\u0131rland\u0131r\u0131r. Samanyolu ve yak\u0131n galaksilerde mesafe \u00f6l\u00e7\u00fcmleri yapabilmek i\u00e7in farkl\u0131 bir \u00f6l\u00e7\u00fcm metodu kullan\u0131lmal\u0131d\u0131r.<\/p>\n

Bir cismin parlakl\u0131\u011f\u0131 ile uzakl\u0131\u011f\u0131 aras\u0131nda ters orant\u0131 vard\u0131r; uzakl\u0131k artt\u0131k\u00e7a cisimlerin parlakl\u0131klar\u0131 azal\u0131r. D\u00fcnya\u2019dan bak\u0131ld\u0131\u011f\u0131nda -\u00e7ok daha parlak y\u0131ld\u0131zlar olmas\u0131na ra\u011fmen- en parlak y\u0131ld\u0131z G\u00fcne\u015f olarak g\u00f6r\u00fcl\u00fcr. Peki farkl\u0131 mesafelerdeki y\u0131ld\u0131zlar\u0131n ger\u00e7ek parlakl\u0131klar\u0131 nas\u0131l belirlenir?<\/p>\n

Elimizde farkl\u0131 parlakl\u0131klarda ve farkl\u0131 uzakl\u0131klarda ampuller olsun. Bu ampullerin parlakl\u0131k s\u0131ralamas\u0131n\u0131 yapman\u0131n en basit yolu onlar\u0131 yan yana getirmektir. B\u00f6ylece hangi ampul\u00fcn daha parlak oldu\u011fu kolayl\u0131kla belirlenebilir. Astronomide de bu y\u00f6ntem kullan\u0131larak y\u0131ld\u0131zlar\u0131n g\u00f6r\u00fcnen parlakl\u0131klar\u0131n\u0131n yan\u0131 s\u0131ra mutlak parlakl\u0131k tan\u0131m\u0131 yap\u0131lm\u0131\u015ft\u0131r. Mutlak parlakl\u0131k, bir y\u0131ld\u0131z\u0131n G\u00fcne\u015f\u2019ten 10 parsek (pc) uzakta oldu\u011fu zaman sahip olaca\u011f\u0131 parlakl\u0131k de\u011feridir (Parsek, 1 yaysaniyelik paralaks a\u00e7\u0131s\u0131ndaki cisim ile G\u00fcne\u015f aras\u0131ndaki mesafedir). G\u00f6r\u00fcnen parlakl\u0131\u011f\u0131n yan\u0131nda mutlak parlakl\u0131\u011f\u0131 da bilinebilen bir cismin -parlakl\u0131\u011f\u0131n uzakl\u0131kla ili\u015fkisi hesaba kat\u0131larak- uzakl\u0131\u011f\u0131 hesaplanabilir. Ancak bunun i\u00e7in mutlak parlakl\u0131\u011f\u0131 de\u011fi\u015fmeyen y\u0131ld\u0131zlara ihtiyac\u0131m\u0131z var.<\/p>\n

Evrendeki baz\u0131 y\u0131ld\u0131z ve y\u0131ld\u0131z olaylar\u0131nda ortaya \u00e7\u0131kan parlakl\u0131kl\u0131\u011f\u0131n b\u00fcy\u00fckl\u00fc\u011f\u00fc, mek\u00e2ndan ba\u011f\u0131ms\u0131zd\u0131r. Bu t\u00fcr nesneler veya g\u00f6k olaylar\u0131, standart mum olarak adland\u0131r\u0131l\u0131r. Standart mumlar, mutlak parlakl\u0131klar\u0131 evrenin her yerinde ayn\u0131 olan g\u00f6kcisimleridir ve uzak mesafe \u00f6l\u00e7\u00fcmlerinin en \u00f6nemli ara\u00e7lar\u0131d\u0131r. Cepheid de\u011fi\u015fkenler olarak adland\u0131r\u0131lan y\u0131ld\u0131zlar da birka\u00e7 10 milyon \u0131\u015f\u0131k y\u0131l\u0131na kadar mesafe \u00f6l\u00e7\u00fcm\u00fc yapabilmeyi sa\u011flayan standart mumlardan bir tanesidir.<\/p>\n

\"\"
\u00dcstte Tip Ia, altta Tip II s\u00fcpernovalar\u0131n olu\u015fum mekanizmalar\u0131.(5)<\/figcaption><\/figure>\n

Zonklayan y\u0131ld\u0131zlar olarak da tan\u0131mlanan cepheid de\u011fi\u015fkenler, 1-70 g\u00fcn gibi belirli k\u0131sa periyotlarla geni\u015fleyip k\u00fc\u00e7\u00fclen y\u0131ld\u0131zlard\u0131r. Parlakl\u0131klar\u0131 ile zonklama periyotlar\u0131 aras\u0131nda ili\u015fki bulunan cepheid de\u011fi\u015fkenlerinin bu \u00f6zelli\u011fi kullan\u0131larak mesafe tayini yap\u0131labilir: \u00d6ncelikle uzakl\u0131\u011f\u0131 hesaplanmak istenen galaksideki cepheidlerin periyotlar\u0131 bulunur. Daha sonra periyot ile mutlak parlakl\u0131k aras\u0131ndaki ili\u015fkiden mutlak parlakl\u0131k bulunur ve buradan da mutlak ve g\u00f6r\u00fcnen parlakl\u0131klar kullan\u0131larak uzakl\u0131k hesaplan\u0131r.<\/p>\n

Cepheidler olduk\u00e7a parlak y\u0131ld\u0131zlar olduklar\u0131ndan galaksimizde ve yak\u0131n galaksilerde g\u00f6zlemlenebilirler. D\u00fcnya\u2019daki teleskoplar, azami 13 milyon \u0131\u015f\u0131k y\u0131l\u0131 uzakl\u0131\u011f\u0131ndaki cepheidleri g\u00f6zlemleyebilirken; uzay g\u00f6zlemleri 56 milyon \u0131\u015f\u0131k y\u0131l\u0131na kadar \u00e7\u0131kabilir.<\/p>\n

\"\"
Doppler etkisi: Kaynak g\u00f6zlemciye yakla\u015ft\u0131k\u00e7a, frekans\u0131 artarken, uzakla\u015ft\u0131k\u00e7a azal\u0131r.(6)<\/figcaption><\/figure>\n

Di\u011fer galaksilerde mesafe \u00f6l\u00e7\u00fcmleri<\/strong><\/p>\n

Cepheid de\u011fi\u015fkenlerin standart mum olarak uzakl\u0131k limitinin olmas\u0131, daha g\u00fc\u00e7l\u00fc bir standart mum ihtiyac\u0131n\u0131 do\u011furur. \u015eansl\u0131y\u0131z ki, 1 milyar \u0131\u015f\u0131k y\u0131l\u0131 uzakl\u0131klara kadar sonu\u00e7 veren b\u00f6yle bir standart mum evrende mevcut. S\u00fcpernova ad\u0131 verilen y\u0131ld\u0131z patlamalar\u0131, ortalama bir y\u0131ld\u0131z\u0131n ya\u015fam\u0131 boyunca yayabilece\u011fi enerjiyi k\u0131sa bir s\u00fcrede a\u00e7\u0131\u011fa \u00e7\u0131karabilir. \u00c7ok uzak mesafelerden g\u00f6zlemlenebilmesi ve karakteristik parlakl\u0131\u011f\u0131, s\u00fcpernovalar\u0131 mesafe \u00f6l\u00e7\u00fcmlerinde gerekli k\u0131lar.<\/p>\n

Y\u0131ld\u0131zlar, hidrostatik dengedeki dev plazma toplar\u0131d\u0131r. K\u00fctle\u00e7ekimi i\u00e7eriye do\u011fru bas\u0131n\u00e7 uygulay\u0131p y\u0131ld\u0131z\u0131 \u00e7\u00f6kertmeye \u00e7al\u0131\u015f\u0131rken, y\u0131ld\u0131z i\u00e7erisindeki n\u00fckleer reaksiyonlar neticesinde olu\u015fan \u0131\u015f\u0131n\u0131m bas\u0131nc\u0131 da buna kar\u015f\u0131 koyar. Bir y\u0131ld\u0131z \u00f6mr\u00fcn\u00fcn b\u00fcy\u00fck k\u0131sm\u0131nda hidrojeni helyuma d\u00f6n\u00fc\u015ft\u00fcrerek \u0131\u015f\u0131n\u0131m bas\u0131nc\u0131 elde eder. Helyuma d\u00f6n\u00fc\u015ft\u00fcrecek hidrojen kalmad\u0131\u011f\u0131nda ise yak\u0131t olarak helyum kullan\u0131l\u0131r ve helyumdan karbon f\u00fczyonu elde edilir. Y\u0131ld\u0131z, k\u0131rm\u0131z\u0131 dev olarak adland\u0131r\u0131lan bu d\u00f6nemde \u00f6nceki boyutlar\u0131n\u0131n birka\u00e7 y\u00fcz kat\u0131na ula\u015f\u0131r. G\u00fcne\u015f gibi g\u00f6rece k\u00fc\u00e7\u00fck k\u00fctleli y\u0131ld\u0131zlar \u00f6mr\u00fcn\u00fc bu d\u00f6nemde sonland\u0131r\u0131r ve y\u0131ld\u0131z\u0131n d\u0131\u015f katmanlar\u0131 gezegensel nebula olarak uzaya sal\u0131n\u0131rken, i\u00e7 k\u0131s\u0131mlar k\u00fctle\u00e7ekimini dengeleyecek bir bas\u0131n\u00e7 olmad\u0131\u011f\u0131ndan beyaz c\u00fcce denilen; karbon ve oksijenden meydana gelen forma \u00e7\u00f6ker. G\u00fcne\u015f\u2019ten 10 kat k\u00fctleli y\u0131ld\u0131zlar i\u00e7in ise farkl\u0131 bir senaryo mevcuttur: K\u0131rm\u0131z\u0131 dev olan y\u0131ld\u0131z element yakmay\u0131 devam ettirir. Element \u00fcretiminde periyodik cetvelde ilerledik\u00e7e her defas\u0131nda daha az enerji a\u00e7\u0131\u011fa \u00e7\u0131kar ve hidrostatik denge i\u00e7in yeterli bas\u0131n\u00e7 sa\u011flanmamaya ba\u015flar. \u00d6mr\u00fcn\u00fcn son 10 milyon y\u0131l\u0131nda silikonu demire d\u00f6n\u00fc\u015ft\u00fcren bu y\u0131ld\u0131zlar, bu noktadan sonra yeterli \u0131\u015f\u0131n\u0131m bas\u0131nc\u0131 \u00fcretemez ve y\u0131ld\u0131z\u0131n i\u00e7 k\u0131s\u0131mlar\u0131 n\u00f6tron y\u0131ld\u0131z\u0131na \u00e7\u00f6kerken, d\u0131\u015f k\u0131s\u0131mlar Tip II s\u00fcpernova ad\u0131 verilen patlamayla uzaya sa\u00e7\u0131l\u0131r. Tip II s\u00fcpernovalar \u00e7o\u011funlukla galaksilerin spiral kollar\u0131nda g\u00f6zlenirken eliptik galaksilerde g\u00f6zlenmez.<\/p>\n

\"\"Tip II s\u00fcpernovalar\u0131n d\u0131\u015f\u0131nda, beyaz c\u00fccelerin patlamas\u0131yla olu\u015fan s\u00fcpernova t\u00fcr\u00fc astronomik a\u00e7\u0131dan daha ilgi \u00e7ekicidir. \u00c7ift y\u0131ld\u0131z sistemindeki bir beyaz c\u00fcce, yan\u0131ndaki e\u015finden k\u00fctle aktar\u0131m\u0131 sonucunda tekrar \u00e7\u00f6k\u00fc\u015fe ge\u00e7ebilir. Karbon ve hidrojenden olu\u015fan beyaz c\u00fcce, \u00e7\u00f6k\u00fc\u015f\u00fcn yaratt\u0131\u011f\u0131 \u00e7ok y\u00fcksek s\u0131cakl\u0131k sonucunda saniyeler i\u00e7inde patlayarak uzaya sa\u00e7\u0131l\u0131r. Nadir ger\u00e7ekle\u015fen bu t\u00fcrdeki patlamalar ise Tip Ia s\u00fcpernova olarak adland\u0131r\u0131l\u0131r. Tip II\u2019lerden 10 ila 100 kat daha parlak olup \u00e7ok uzak mesafelerden g\u00f6zlenebilen Tip Ia s\u00fcpernovalar\u0131n karakteristik bir parlakl\u0131\u011fa sahip olmas\u0131 da onlar\u0131 e\u015fsiz bir mesafe \u00f6l\u00e7\u00fcc\u00fc yapar.<\/p>\n

T\u0131pk\u0131 cepheid de\u011fi\u015fkenlerde oldu\u011fu gibi Tip Ia s\u00fcpernovalar\u0131n mutlak ve g\u00f6r\u00fcnen parlakl\u0131klar\u0131 kar\u015f\u0131la\u015ft\u0131r\u0131l\u0131r ve uzakl\u0131k ile parlakl\u0131k aras\u0131ndaki ili\u015fki g\u00f6z \u00f6n\u00fcne al\u0131n\u0131rsa, s\u00fcpernovan\u0131n ger\u00e7ekle\u015fti\u011fi galaksinin uzakl\u0131\u011f\u0131 hesaplanabilir.<\/p>\n

Uzak mesafe \u00f6l\u00e7\u00fcmleri<\/strong><\/p>\n

1 milyar \u0131\u015f\u0131k y\u0131l\u0131ndan daha uzak mesafelerde yukar\u0131da bahsedilen y\u00f6ntemlerden hi\u00e7biri \u00e7al\u0131\u015fmaz. Bu noktadan itibaren g\u00f6zlemin yan\u0131nda teori de devreye girmektedir.
\nAmbulans sirenlerini yakla\u015ft\u0131k\u00e7a daha tiz; uzakla\u015ft\u0131k\u00e7a daha bas duyar\u0131z. Hareketli kayna\u011f\u0131n frekans\u0131n\u0131n g\u00f6zlemciye g\u00f6re de\u011fi\u015fmesi, Doppler etkisi olarak adland\u0131r\u0131lan fiziksel bir fenomendir ve ayn\u0131 \u015fey \u0131\u015f\u0131k dalgalar\u0131 i\u00e7in de ge\u00e7erlidir: G\u00f6zlemciden uzakla\u015fan \u0131\u015f\u0131\u011f\u0131n frekans\u0131 azal\u0131rken, yakla\u015fan \u0131\u015f\u0131\u011f\u0131n frekans\u0131 ise artar. Frekanstaki azalma k\u0131z\u0131la kayma; artma ise maviye kayma olarak adland\u0131r\u0131l\u0131r.<\/p>\n

Bunun yan\u0131 s\u0131ra ba\u015fka \u00f6nemli nokta da kuantum fizi\u011finin bir sonucundan kar\u015f\u0131m\u0131za \u00e7\u0131kar: Her elementin belirli bir \u0131\u015f\u0131ma spektrumu vard\u0131r ve bu spektrum evrenin her noktas\u0131nda ayn\u0131 olmal\u0131d\u0131r. Karakteristik \u0131\u015f\u0131ma spektrumlar\u0131 incelenerek, incelenen maddenin i\u00e7eri\u011fi hakk\u0131nda bilgi sahibi olunabilir. Doppler etkisi ve karakteristik spektrumlar bir araya getirildi\u011finde, cisimlerin uzakl\u0131\u011f\u0131 hakk\u0131nda fikir sahibi olabiliriz.<\/p>\n

1929\u2019da Edwin Hubble, galaksilerden gelen \u0131\u015f\u0131k spektrumlar\u0131n\u0131 inceledi\u011finde, k\u0131z\u0131la kayma g\u00f6zlemledi. Bunun \u00f6tesinde, uzak galaksilerdeki k\u0131z\u0131la kayma oran\u0131 yak\u0131nlara nazaran daha fazlayd\u0131. K\u0131z\u0131la kayman\u0131n sebebi olan Doppler etkisi gere\u011fince yak\u0131n galaksiler daha d\u00fc\u015f\u00fck, uzak galaksiler ise daha y\u00fcksek h\u0131zlarda uzakla\u015fmaktayd\u0131 ki, bu da evrenin geni\u015flemesi anlam\u0131na gelmekteydi.<\/p>\n

Galaksilerin uzakla\u015fma h\u0131zlar\u0131n\u0131n uzakl\u0131\u011fa ba\u011fl\u0131 grafi\u011fini \u00e7izen Hubble, \u015fimdi Hubble yasas\u0131 olarak bildi\u011fimiz ba\u011f\u0131nt\u0131y\u0131 ortaya koydu. Ba\u011f\u0131nt\u0131ya g\u00f6re galaksilerin uzakla\u015fma h\u0131zlar\u0131, uzakl\u0131\u011f\u0131n Hubble parametresi ile \u00e7arp\u0131m\u0131na e\u015fittir. Hubble parametresi h\u00e2l\u00e2 tart\u0131\u015f\u0131lmakla birlikte, megaparsek ba\u015f\u0131na saniyede yakla\u015f\u0131k 65 kilometre oldu\u011fu d\u00fc\u015f\u00fcn\u00fclmektedir. Buna g\u00f6re 1 megaparsek (1 mega parsek =3.260.000 \u0131\u015f\u0131k y\u0131l\u0131) uzaktaki bir nesne, bizden saniyede 65 kilometre h\u0131zla uzakla\u015facakt\u0131r. Mesafe b\u00fcy\u00fcd\u00fck\u00e7e uzakla\u015fma h\u0131z\u0131 daha da artar.<\/p>\n

Hubble yasas\u0131na g\u00f6re, bir galaksinin uzakl\u0131\u011f\u0131n\u0131 bulabilmek i\u00e7in sadece uzakla\u015fma h\u0131z\u0131n\u0131 bulmak yeterli olacakt\u0131r. Uzakla\u015fma h\u0131z\u0131 da spektrumlardaki k\u0131z\u0131la kaymaya bak\u0131larak basit bir \u015fekilde elde edilebilir. Sonu\u00e7 olarak galaksilerin k\u0131z\u0131la kaymalar\u0131 g\u00f6zlenerek uzakl\u0131\u011f\u0131 hesaplanabilir.<\/p>\n

Kaynaklar<\/strong><\/p>\n

1) http:\/\/www.nrao.edu\/pr\/2007\/mercury\/mercradar.jpg
\n2) http:\/\/80.251.40.59\/science.ankara.edu.tr\/selam\/TR\/ast404\/Bolum_11a_Yildizlarin_Uzakliklari.pdf
\n3) http:\/\/hyperphysics.phy-astr.gsu.edu\/hbase\/astro\/imgast\/maslumcep.gif
\n4) http:\/\/cseligman.com\/text\/stars\/cepheid.jpg
\n5) http:\/\/hyperphysics.phy-astr.gsu.edu\/hbase\/astro\/astpic\/supnovform.jpg
\n6) http:\/\/www.teachastronomy.com\/astropediaimages\/Doppler_effect_diagrammatic.png
\n7) http:\/\/www.wwu.edu\/depts\/skywise\/img\/hubbles_law.gif
\n8) http:\/\/telescopes.stardate.org\/images\/research\/scaling_the_universe_ladder.jpg<\/p>\n","protected":false},"excerpt":{"rendered":"

Mesafe \u00f6l\u00e7\u00fcmleri g\u00fcnl\u00fck hayatta al\u0131\u015f\u0131k oldu\u011fumuz boyutlarda kolayd\u0131r; bir masan\u0131n uzunlu\u011funu basit bir cetvel kullanarak rahatl\u0131kla \u00f6l\u00e7ebiliriz. Ancak mesafeler k\u00fc\u00e7\u00fcld\u00fck\u00e7e veya b\u00fcy\u00fcd\u00fck\u00e7e, elimizdeki cetvellerin hassasiyeti yetersiz olmaya ba\u015flar. G\u00fcne\u015f\u2019in D\u00fcnya\u2019ya olan uzakl\u0131\u011f\u0131n\u0131 hi\u00e7bir cetvelle \u00f6l\u00e7emeyiz. Yap\u0131lmas\u0131 gereken, fizik yasalar\u0131n\u0131 kullanarak elde edilmi\u015f yeni bir astronomik cetvel icat etmektir. Ancak bu astronomik cetvel de daha uzak […]<\/p>\n","protected":false},"author":634,"featured_media":21233,"comment_status":"closed","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"_acf_changed":false,"footnotes":""},"categories":[173,30,26],"tags":[657,288,291,2549,2550,1748,404],"class_list":["post-21232","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-136-sayi","category-astronomi","category-fizik","tag-evren","tag-fizik","tag-galaksiler","tag-mesafeler","tag-olcum","tag-samanyolu","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