Astronomi Hollywood korku filmlerine benzemez. Bilim bir ke\u015fif ve ayd\u0131nlanma maceras\u0131d\u0131r, ama Vanderbilt \u00dcniversitesi\u2019ndeki astronomlar\u0131n son ke\u015ffinin korku filmlerini and\u0131rd\u0131\u011f\u0131n\u0131 s\u00f6yleyebiliriz.<\/p>\n
\u00c7\u00fcnk\u00fc bilim adamlar\u0131 uzayda do\u011fan gen\u00e7 d\u00fcnyalar\u0131 yutan yamyam y\u0131ld\u0131zlar ke\u015ffettiler. HD 20781 ve HD 20782 adl\u0131 iki y\u0131ld\u0131z toplam 30 gezegeni yutarak yok etti.<\/p>\n
Anla\u015f\u0131lan, uzayda hayat aray\u0131\u015f\u0131nda \u00f6nemli olan \u015fey galaksimizde D\u00fcnya benzeri ka\u00e7 gezegenin olu\u015ftu\u011fu de\u011fil. As\u0131l \u00f6nemli olan bu kayal\u0131k gezegenlerden ka\u00e7\u0131n\u0131n hayatta kald\u0131\u011f\u0131. D\u00fcnya yutan yamyam g\u00fcne\u015fler bir\u00e7ok gezegeni i\u00e7ine \u00e7ekerek yok ediyor ve Evren\u2019deki olas\u0131 \u201cD\u00fcnya\u201d say\u0131s\u0131n\u0131 azalt\u0131yor. Peki neden?<\/p>\n
Gezegen g\u00fcden uzay \u00e7obanlar\u0131:<\/strong><\/span><\/p>\n D\u00fcnya benzeri kayal\u0131k gezegenler i\u00e7 g\u00fcne\u015f sisteminde, y\u0131ld\u0131za yak\u0131n mesafelerde olu\u015fuyor. J\u00fcpiter gibi gaz devleri ise so\u011fuk d\u0131\u015f g\u00fcne\u015f sisteminde ortaya \u00e7\u0131k\u0131yor.<\/p>\n Gaz devlerinin binlerce kilometre kal\u0131nl\u0131\u011f\u0131nda bir atmosfer olu\u015fturmas\u0131n\u0131n sebebi de bu gezegenlerin g\u00fcne\u015fe uzak olmas\u0131. Yoksa g\u00fcne\u015fin yayd\u0131\u011f\u0131 \u0131s\u0131dan kaynaklanan buharla\u015fma, gaz devi olmaya aday iri kayal\u0131k gezegenlerin kal\u0131n bir atmosfer olu\u015fturmas\u0131n\u0131 engellerdi.<\/p>\n \u0130\u015fin ilginci d\u00fcnya benzeri k\u00fc\u00e7\u00fck kayal\u0131k gezegenler de hayat\u0131n\u0131 gaz devlerine bor\u00e7lu. Gaz devleri d\u0131\u015f g\u00fcne\u015f sisteminde kal\u0131rsa, kayal\u0131k d\u00fcnyalar\u0131 asteroit \u00e7arp\u0131\u015fmalar\u0131ndan koruyor. G\u00fc\u00e7l\u00fc bir \u00e7ekim alan\u0131na sahip olan gaz devleri \u00e7ok say\u0131da asteroit ve kuyrukluy\u0131ld\u0131z\u0131 kendine \u00e7ekerek, D\u00fcnya benzeri gezegenlerde g\u00f6kta\u015f\u0131 \u00e7arp\u0131\u015fmalar\u0131n\u0131 azalt\u0131yor.<\/p>\n \u00d6rne\u011fin J\u00fcpiter olmasayd\u0131, D\u00fcnyam\u0131zda dinozorlar\u0131n t\u00fckenmesine yol a\u00e7an b\u00fcy\u00fck \u00e7arp\u0131\u015fmalar 60 milyon y\u0131lda de\u011fil, 10 milyon y\u0131lda bir ya\u015fanacakt\u0131. Bu da D\u00fcnya\u2019da hayat\u0131n t\u00fckenmesine yol a\u00e7acakt\u0131.<\/p>\n Ancak gaz devleri iki ucu keskin k\u0131l\u0131\u00e7: D\u0131\u015f g\u00fcne\u015f sisteminde olu\u015ftuktan sonra i\u00e7 g\u00fcne\u015f sistemine g\u00f6\u00e7 ederlerse, g\u00fcne\u015fe yak\u0131n kayal\u0131k d\u00fcnyalar\u0131 yerinden ediyor ve y\u00f6r\u00fcngeden \u00e7\u0131kararak y\u0131ld\u0131z\u0131n i\u00e7ine d\u00fc\u015fmesine neden oluyorlar. Yamyam y\u0131ld\u0131zlar i\u015fte bu \u015fekilde ortaya \u00e7\u0131k\u0131yor ve D\u00fcnya gibi gezegenleri yutarak o y\u0131ld\u0131z sisteminde hayat\u0131n ortaya \u00e7\u0131kma \u015fans\u0131n\u0131 azalt\u0131yor.<\/p>\n Galaktik besin zinciri:<\/strong><\/span><\/p>\n Galaksimizde G\u00fcne\u015f benzeri yeterli say\u0131da G s\u0131n\u0131f\u0131 sar\u0131 c\u00fcce y\u0131ld\u0131z bulduk. Sadece Kepler uzay teleskopuyla g\u00fcne\u015f sisteminin d\u0131\u015f\u0131nda 960 gezegen ke\u015ffettik. D\u00fcnya\u2019daki teleskoplar\u0131 da i\u015fin i\u00e7ine katarsak 20 y\u0131lda 2800 \u00f6te d\u00fcnya tespit etmi\u015f bulunuyoruz. \u00dcstelik bunlar\u0131n aras\u0131nda D\u00fcnya benzeri kayal\u0131k gezegenler de yer al\u0131yor.<\/p>\n Bu ke\u015fifler yak\u0131n zamana kadar bilim adamlar\u0131na uzayda D\u00fcnya benzeri hayat bulma konusunda \u00fcmit veriyordu. Ne de olsa \u00f6te d\u00fcnya ke\u015ffetmekte kulland\u0131\u011f\u0131m\u0131z y\u00f6ntemler k\u00fc\u00e7\u00fck kayal\u0131k gezegenlerden \u00e7ok, J\u00fcpiter gibi gaz devlerini bulmaya elveri\u015fliydi. Bu y\u00fczden galakside kayal\u0131k gezegen say\u0131s\u0131 bekledi\u011fimizden az \u00e7\u0131kt\u0131\u011f\u0131 zaman, \u201cSorun de\u011fil, uzayda D\u00fcnya benzeri gezegenler var ama biz g\u00f6remiyoruz\u201d dedik.<\/p>\n Peki, ya yan\u0131l\u0131yorsak? Ya uzayda D\u00fcnya benzeri \u00e7ok az gezegen varsa? O zaman galaksimizde D\u00fcnya benzeri hayat bulma \u015fans\u0131m\u0131z da azalacakt\u0131r. Bu durumda James Cameron\u2019\u0131n Avatar filmindeki Pandora gibi hayat dolu d\u00fcnyalar bulma hayaline elveda diyebiliriz.<\/p>\n Samanyolu\u2019ndaki g\u00fcne\u015f benzeri y\u0131ld\u0131zlar\u0131n \u00e7o\u011fu yeni olu\u015fan kayal\u0131k gezegenleri bu yaz\u0131da anlatt\u0131\u011f\u0131m\u0131z gibi yiyip yutuyorsa, Evren insano\u011flu i\u00e7in ger\u00e7ekten yaln\u0131zl\u0131k dolu \u0131ss\u0131z bir yer olmal\u0131. Peki, \u00f6yle mi ger\u00e7ekten? Uzay\u0131n derinliklerinde s\u0131ra d\u0131\u015f\u0131 bir yolculu\u011fa \u00e7\u0131karak birlikte g\u00f6relim.<\/p>\n Y\u0131ld\u0131zlar\u0131n yemek al\u0131\u015fkanl\u0131klar\u0131:<\/strong><\/span><\/p>\n Her \u015fey Vanderbilt \u00dcniversitesi Astronomi Profes\u00f6r\u00fc Keivan Stassun ve ekibinin yabanc\u0131 y\u0131ld\u0131zlar\u0131n atmosferinde buharla\u015fm\u0131\u015f kayal\u0131k gezegenlerden kalma kimyasal izler bulmas\u0131yla ba\u015flad\u0131.<\/p>\n Y\u0131ld\u0131zlar\u0131n atmosferinin kimyasal yap\u0131s\u0131n\u0131 \u00f6\u011frenmek i\u00e7in y\u0131ld\u0131z \u0131\u015f\u0131\u011f\u0131 tayf\u0131n\u0131 analiz eden Vanderbilt \u00dcniversitesi Y\u00fcksek Lisans \u00f6\u011frencisi Trey Mack; D\u00fcnya, Mars ve Ven\u00fcs gibi kayal\u0131k gezegenleri yutan y\u0131ld\u0131zlar\u0131n atmosfer kimyas\u0131n\u0131n nas\u0131l de\u011fi\u015fece\u011fini g\u00f6steren bir matematik modeli geli\u015ftirdi.<\/p>\n Y\u0131ld\u0131zlar\u0131n atmosferindeki elementleri tek tek analiz etmemizi sa\u011flayan bu model, uzayda yeni d\u00fcnyalar\u0131n nas\u0131l olu\u015ftu\u011funu anlamam\u0131z\u0131 sa\u011flayacak ve b\u00f6ylece galaksideki D\u00fcnya benzeri \u00f6te gezegenleri saptamay\u0131 kolayla\u015ft\u0131racak.<\/p>\n Astronomlar Mack\u2019\u0131n modelini test etmek i\u00e7in HD 20781 ve HD 20782 adl\u0131 G\u00fcne\u015f benzeri iki y\u0131ld\u0131z\u0131 se\u00e7tiler. Teleskoplar\u0131n\u0131 y\u00f6nelttikleri bu y\u0131ld\u0131zlar 3 adet gaz devi i\u00e7eren ilgin\u00e7 bir \u00e7ift y\u0131ld\u0131z sistemi olu\u015fturuyordu.<\/p>\n \u00d6ted\u00fcnya avc\u0131lar\u0131:<\/strong><\/span><\/p>\n 1990\u2019lardan itibaren teleskop teknolojisi bilgisayar deste\u011fiyle geli\u015fti ve y\u0131ld\u0131zlar\u0131n \u00e7evresinde d\u00f6nen gezegenleri dolayl\u0131 yollardan tespit etmek m\u00fcmk\u00fcn oldu. Bilim adamlar\u0131 o zamandan beri y\u0131ld\u0131z atmosferindeki metal oran\u0131n\u0131 g\u00fcne\u015f sisteminde kayal\u0131k gezegen bulunma ihtimaliyle ili\u015fkilendirecek bir model geli\u015ftirmek istiyordu.<\/p>\n \u0130\u015fte Mack\u2019in modeli bu i\u015fe yar\u0131yor. Y\u0131ld\u0131z \u0131\u015f\u0131\u011f\u0131n\u0131n tayf\u0131na bakan astrofizik\u00e7ilerin bir y\u0131ld\u0131z\u0131n atmosferinin \u00fcst katmanlardaki elementleri analiz etmesini sa\u011fl\u0131yor. Zaten bilim adamlar\u0131 yaz\u0131m\u0131za konu olan yamyam y\u0131ld\u0131zlar\u0131 da b\u00f6yle ke\u015ffettiler.<\/p>\n Evren metal m\u00fczik seviyor:<\/strong><\/span><\/p>\n Evren\u2019de gezegenlerin olu\u015fmas\u0131n\u0131 ve D\u00fcnya\u2019da hayat\u0131n ortaya \u00e7\u0131kmas\u0131n\u0131 bir varolu\u015f senfonisi olarak hayal edersek, y\u0131ld\u0131zlar\u0131n da metal m\u00fczik sevdi\u011fini kabul etmemiz gerekir. \u00c7\u00fcnk\u00fc ABD Los Alamos Ulusal Laboratuar\u0131\u2019nda yap\u0131lan bir ara\u015ft\u0131rmada, y\u00fcksek oranda metal i\u00e7eren y\u0131ld\u0131zlar\u0131n gezegen sistemi geli\u015ftirme ihtimalinin de y\u00fcksek oldu\u011fu ortaya \u00e7\u0131kt\u0131.<\/p>\n Atmosferinde az miktarda metal bulunan y\u0131ld\u0131zlar\u0131n gezegen sahibi olma olas\u0131l\u0131\u011f\u0131 ise daha d\u00fc\u015f\u00fckt\u00fc. Ancak d\u00fc\u015f\u00fck metal i\u00e7eren y\u0131ld\u0131zlar\u0131n \u00e7evresindeki az say\u0131da kayal\u0131k gezegenin hayatta kalarak g\u00fcn\u00fcm\u00fcze gelme olas\u0131l\u0131\u011f\u0131 y\u00fcksekti.<\/p>\n Ku\u015fak \u00e7at\u0131\u015fmas\u0131:<\/strong><\/span><\/p>\n Evren\u2019in olu\u015fumuna bakt\u0131\u011f\u0131m\u0131z zaman neden b\u00f6yle oldu\u011funu g\u00f6r\u00fcyoruz. Atmosferinde metal i\u00e7eren ikinci ku\u015fak y\u0131ld\u0131zlar 10 milyar y\u0131l \u00f6nce ortaya \u00e7\u0131kmadan evvel, Evren hayata elveri\u015fli olmayan \u0131ss\u0131z bir yerdi.<\/p>\n \u00c7\u00fcnk\u00fc Evren\u2019i do\u011furan B\u00fcy\u00fck Patlama\u2019n\u0131n ard\u0131ndan ortaya \u00e7\u0131kan y\u0131ld\u0131zlar sadece hidrojen ve helyumdan olu\u015fuyordu. Metaller ve kayal\u0131k d\u00fcnyay\u0131 olu\u015fturan silikon ile karbon gibi elementler o \u00e7a\u011flarda yoktu.<\/p>\n Ancak, birka\u00e7 y\u00fcz milyon y\u0131l i\u00e7inde s\u00fcpernova olarak patlay\u0131p yok olan ilk ku\u015fak y\u0131ld\u0131zlar n\u00fckleer f\u0131r\u0131nlar\u0131nda, yani y\u0131ld\u0131z \u00e7ekirdeklerinde evrenin ilk a\u011f\u0131r elementlerini olu\u015fturdular. Ard\u0131ndan \u00e7arp\u0131\u015fan n\u00f6tron y\u0131ld\u0131zlar\u0131 alt\u0131n gibi a\u011f\u0131r metalleri olu\u015fturdu.<\/p>\n B\u00f6ylece 10 milyar y\u0131l \u00f6nce ikinci ku\u015fak y\u0131ld\u0131zlar ortaya \u00e7\u0131kt\u0131. Bu \u201cmetalik y\u0131ld\u0131zlar\u0131\u201d ve \u00e7evrelerindeki gezegenleri olu\u015fturan gaz ve toz bulutunda a\u011f\u0131r elementler bulunuyordu. \u0130lk kayal\u0131k gezegenler ve belki de Yery\u00fcz\u00fcnden \u00f6nce hayat bar\u0131nd\u0131ran ata d\u00fcnyalar Evren\u2019e bu \u015fekilde merhaba dedi.<\/p>\n Ger\u00e7i bu y\u00fcksek oranda metal i\u00e7eren y\u0131ld\u0131zlar\u0131n neden \u00e7ok say\u0131da kayal\u0131k gezegen bar\u0131nd\u0131rd\u0131\u011f\u0131n\u0131 a\u00e7\u0131kl\u0131yor, ama d\u00fc\u015f\u00fck metal i\u00e7eren y\u0131ld\u0131zlar\u0131n \u00e7evresindeki kayal\u0131k gezegenlerin neden uzun \u00f6m\u00fcrl\u00fc oldu\u011funu a\u00e7\u0131klam\u0131yor. Bunun i\u00e7in uzay maceras\u0131na devam etmemiz gerekiyor.<\/p>\n S\u0131cak J\u00fcpiter ne demek?<\/strong><\/span><\/p>\n J\u00fcpiter\u2019i al\u0131n ve G\u00fcne\u015f\u2019e yakla\u015ft\u0131r\u0131n. Hatta G\u00fcne\u015f\u2019e Merk\u00fcr gezegeninden daha yak\u0131n olsun. Belki 30 milyon kilometre. J\u00fcpiter\u2019in atmosferi g\u00fcne\u015fin s\u0131ca\u011f\u0131 y\u00fcz\u00fcnden buharla\u015fmaya ba\u015flayacak ve J\u00fcpiter\u2019de sesten h\u0131zl\u0131 esen kas\u0131rgalar kopacakt\u0131r. Evet, saatte 1600 km h\u0131zla esen kas\u0131rgalar (ki bu da yakla\u015f\u0131k olarak D\u00fcnya\u2019n\u0131n kendi etraf\u0131nda d\u00f6nme h\u0131z\u0131na e\u015fittir).<\/p>\n S\u0131cak J\u00fcpiterler i\u015fte bu nedenle biz insanlar i\u00e7in favori tatil mek\u00e2nlar\u0131 de\u011fil. Ancak S\u0131cak J\u00fcpiterlerden s\u00f6z ederek konuyu da\u011f\u0131tt\u0131\u011f\u0131m\u0131z\u0131 da d\u00fc\u015f\u00fcnmeyin. Sadece J\u00fcpiter\u2019in G\u00fcne\u015f\u2019e yakla\u015f\u0131rken G\u00fcne\u015f Sistemi\u2019nde nas\u0131l bir felaket ya\u015fanaca\u011f\u0131n\u0131 d\u00fc\u015f\u00fcn\u00fcn!<\/p>\n J\u00fcpiter\u2019in k\u00fctlesi di\u011fer b\u00fct\u00fcn gezegenlerin k\u00fctlesinin toplam\u0131ndan daha fazla ve bu gezegen G\u00fcne\u015f\u2019e yakla\u015f\u0131rken D\u00fcnya, Ven\u00fcs, Mars ile Merk\u00fcr\u2019\u00fc y\u00f6r\u00fcngesinden \u00e7\u0131karacak. Ya bu kayal\u0131k gezegenler uzay\u0131n derinliklerine savrulup karanl\u0131kta donarak kaybolacak ya da G\u00fcne\u015f\u2019e \u00e7ok yakla\u015f\u0131p i\u00e7ine d\u00fc\u015ferek yok olacak.<\/p>\n Az\u0131 karar, \u00e7o\u011fu zarar:<\/strong><\/span><\/p>\n \u0130\u015fte bu y\u00fczden atmosferinde y\u00fcksek oranda metal olan y\u0131ld\u0131zlar\u0131n \u00e7evresinde \u00e7ok say\u0131da gezegen olma ihtimali y\u00fcksek, ama kayal\u0131k gezegen bulunma olas\u0131l\u0131\u011f\u0131 d\u00fc\u015f\u00fck. Yine de bu k\u0131sa cevap sizi tatmin etmezse, detaylar\u0131 hemen a\u015fa\u011f\u0131da.<\/p>\n G\u00fcne\u015f Sistemi\u2019nin ilk y\u0131llar\u0131nda gen\u00e7 gezegenler hen\u00fcz yerine \u201ctam olarak oturmam\u0131\u015ft\u0131\u201d ve y\u00f6r\u00fcngeleri s\u00fcrekli de\u011fi\u015fiyordu. Ancak, G\u00fcne\u015f Sistemi\u2019nde metal oran\u0131 d\u00fc\u015f\u00fck oldu\u011fu i\u00e7in az say\u0131da d\u00fcnya olu\u015ftu ve bu d\u00fcnyalar di\u011fer gezegenler taraf\u0131ndan pek rahats\u0131z edilmediklerinden kararl\u0131 y\u00f6r\u00fcngelere oturdular. B\u00f6ylece J\u00fcpiter gibi gaz devleri taraf\u0131ndan yanl\u0131\u015fl\u0131kla G\u00fcne\u015f\u2019in i\u00e7ine savrulmad\u0131lar.<\/p>\n Orta karar y\u0131ld\u0131zlar:<\/strong><\/span><\/p>\n Bilim adamlar\u0131 deneysel y\u00f6ntemler kullanmad\u0131\u011f\u0131 i\u00e7in Eski Yunan filozofu Aristoteles\u2019i pek sevmezler; ama Aristoteles\u2019in ender d\u00e2hilerden oldu\u011fu kesin. Neden derseniz, \u201cAlt\u0131n Orta\u201ddan bahsetmi\u015f derim. Aristoteles hayatta a\u015f\u0131r\u0131 u\u00e7lardan sak\u0131nmam\u0131z\u0131 sal\u0131k verirdi.<\/p>\n San\u0131r\u0131m hayat\u0131n be\u015fi\u011fi olan D\u00fcnya\u2019n\u0131n da a\u015f\u0131r\u0131l\u0131ktan sak\u0131nan bir s\u0131radan y\u0131ld\u0131z\u0131n \u00e7evresinde olu\u015ftu\u011funu \u00f6\u011frense sevinirdi. G\u00fcne\u015f \u201cmetalik bir y\u0131ld\u0131z\u201d ama metal oran\u0131 ne y\u00fcksek ne de \u00e7ok d\u00fc\u015f\u00fck: Orta karar.<\/p>\n Kur\u015fun gezegen?<\/strong><\/span><\/p>\n Trey Mack, y\u0131ld\u0131zlardaki metal oran\u0131n\u0131 \u00f6l\u00e7en yeni matematik modelini geli\u015ftirmek i\u00e7in Tampa \u00dcniversitesi\u2019nden Simon Schuler\u2019\u0131n \u00e7al\u0131\u015fmalar\u0131ndan yararland\u0131 ve ilk olarak y\u0131ld\u0131zlardaki al\u00fcminyum, silikon, kalsiyum gibi 15 elementin kesin oranlar\u0131n\u0131 \u00f6l\u00e7meye karar verdi. Bunun bir sebebi vard\u0131.<\/p>\n G\u00fcne\u015f\u2019in y\u00fczey s\u0131cakl\u0131\u011f\u0131 6000 derece ve D\u00fcnyam\u0131z gibi uzaydaki di\u011fer kayal\u0131k gezegenler de G\u00fcne\u015f\u2019e nispeten yak\u0131n mesafelerde bulunuyor. Dolay\u0131s\u0131yla kayal\u0131k gezegenlerin g\u00fcne\u015fin s\u0131ca\u011f\u0131nda kolay erimeyen elementlerden olu\u015fmas\u0131 gerekiyor.<\/p>\n G\u00fcne\u015f\u2019e yaln\u0131zca 58 milyon km uzakta olan Merk\u00fcr bile kaya ve demirden olu\u015ftu\u011fu i\u00e7in erimeden varl\u0131\u011f\u0131n\u0131 s\u00fcrd\u00fcr\u00fcyor. Nitekim demir 1500 derecede, granit ise yakla\u015f\u0131k 700 derecede eriyor. Oysa kur\u015funun erime s\u0131cakl\u0131\u011f\u0131 sadece 320 derece ve i\u015fte bu y\u00fczden uzayda kur\u015fundan gezegenler bulunmuyor.<\/p>\n Kayal\u0131k gezegenler \u00f6ncelikle silikat, karbon ve elmastan olu\u015fuyor. Hatta bol miktarda karbon i\u00e7eren gezegenler dev elmas toplar\u0131na d\u00f6n\u00fc\u015f\u00fcyor. D\u00fcnyam\u0131z ise asl\u0131nda karbon bak\u0131m\u0131ndan fakir bir gezegen.<\/p>\n Bildi\u011finiz gibi bizde elmas da\u011flar\u0131 yok. Bunun yerine bol kaya (silikat) ve b\u00fcy\u00fck bir demir\u2013nikel \u00e7ekirdek var. Buna ra\u011fmen az miktarda karbon atomu D\u00fcnya\u2019da hayat\u0131n ortaya \u00e7\u0131kmas\u0131na yeterli oldu. : )<\/p>\n Karde\u015f y\u0131ld\u0131zlar\u0131n gizemi:<\/strong><\/span><\/p>\n HD 20781\u2013HD 20782 \u00e7ift y\u0131ld\u0131z sistemi, uzayda gezegen yutan g\u00fcne\u015flerle yeni d\u00fcnyalar\u0131n olu\u015fumu aras\u0131ndaki ili\u015fkiyi incelemek a\u00e7\u0131s\u0131ndan idealdi. \u0130kiz y\u0131ld\u0131zlar ayn\u0131 gaz ve toz bulutundan olu\u015ftu\u011fu i\u00e7in kimyasal yap\u0131lar\u0131n\u0131n benzer olmas\u0131 gerekiyordu.<\/p>\n Y\u00fcksek oranda metal i\u00e7eren karde\u015f y\u0131ld\u0131zlarla ilgili en \u00f6nemli ke\u015fif ise, her iki y\u0131ld\u0131z\u0131n da gezegen sahibi olmas\u0131yd\u0131 ve bu astronomi tarihi a\u00e7\u0131s\u0131ndan bir ilkti: Bilim adamlar\u0131 \u00e7ift y\u0131ld\u0131z sistemlerinde gezegen olma ihtimalinin d\u00fc\u015f\u00fck oldu\u011funu tahmin ediyordu. \u00c7\u00fcnk\u00fc y\u0131ld\u0131zlar\u0131n yer\u00e7ekiminin mevcut gezegenleri y\u00f6r\u00fcngeden \u00e7\u0131karmas\u0131 gerekirdi. Oysa bu y\u0131ld\u0131z sisteminde toplam \u00fc\u00e7 gaz devi olmas\u0131na kar\u015f\u0131n hi\u00e7 kayal\u0131k gezegen yoktu.<\/p>\n Bu durumda y\u0131ld\u0131zlar\u0131n atmosferinde y\u00fcksek s\u0131cakl\u0131klarda eriyen bol miktarda metal olmas\u0131n\u0131n nedeni belliydi. Yamyam y\u0131ld\u0131zlar y\u00fcksek metal oran\u0131na ba\u011fl\u0131 olarak \u00e7ift g\u00fcne\u015f sisteminde olu\u015fan \u00e7ok say\u0131daki kayal\u0131k gezegeni yutmu\u015ftu. Hem de yak\u0131n zamanda! Bu olay milyarlarca y\u0131l \u00f6nce meydana gelseydi, gezegenlerin kal\u0131nt\u0131s\u0131 olan metaller y\u0131ld\u0131z\u0131n i\u00e7 katmanlar\u0131na do\u011fru \u00e7\u00f6kecek ve atmosferde bu kadar y\u00fcksek oranda bulunmayacakt\u0131.<\/p>\n Mack, Schuler ve Stassun, G\u00fcne\u015f\u2019e benzeyen sar\u0131 y\u0131ld\u0131zlardan olu\u015fan bu \u00e7ift y\u0131ld\u0131z sistemini yak\u0131ndan incelemeye karar verdiler. Uzayda hayat aray\u0131\u015f\u0131nda D\u00fcnya\u2019ya benzer gezegenlerin olu\u015fma ihtimalini de\u011ferlendirmek \u00fczere, gezegen yiyen yamyam y\u0131ld\u0131zlara yak\u0131ndan g\u00f6z atmalar\u0131 gerekiyordu.<\/p>\n Sar\u0131 c\u00fcceler:<\/strong><\/span><\/p>\n 1 milyon 390 milyon km \u00e7ap\u0131yla G\u00fcne\u015f sadece 12 bin km geni\u015flikte olan D\u00fcnya\u2019n\u0131n yan\u0131nda g\u00f6z\u00fcm\u00fcze b\u00fcy\u00fck geliyor; ama Evren\u2019deki di\u011fer y\u0131ld\u0131zlarla kar\u015f\u0131la\u015ft\u0131r\u0131ld\u0131\u011f\u0131nda, G\u00fcne\u015fimizin asl\u0131nda G s\u0131n\u0131f\u0131 bir sar\u0131 c\u00fcce oldu\u011funu g\u00f6r\u00fcyoruz. Ara\u015ft\u0131rmam\u0131za konu olan HD 20781 ile HD 20782 y\u0131ld\u0131zlar\u0131 da D\u00fcnya benzeri gezegen bulundurma \u015fans\u0131 olan fakat bu d\u00fcnyalar\u0131 yutan iki yamyam sar\u0131 c\u00fcce olarak ilgi \u00e7ekiyor.<\/p>\n Bunlardan birinin y\u00f6r\u00fcngesinde Nept\u00fcn boyutunda iki gaz devi bulunuyor. Di\u011fer y\u0131ld\u0131z\u0131n \u00e7evresinde ise eliptik y\u00f6r\u00fcngede d\u00f6nen ve J\u00fcpiter b\u00fcy\u00fckl\u00fc\u011f\u00fcnde olan bir gezegen var. Bu gezegen y\u00f6r\u00fcnge turu s\u0131ras\u0131nda y\u0131ld\u0131za \u00e7ok yakla\u015f\u0131yor ve S\u0131cak J\u00fcpiter\u2019e d\u00f6n\u00fc\u015f\u00fcyor. Uzakla\u015ft\u0131\u011f\u0131nda ise G\u00fcne\u015f Sistemi\u2019ndeki Nept\u00fcn gibi so\u011fuk bir gaz devi haline geliyor.<\/p>\n Astronomlar J\u00fcpiter benzeri b\u00fcy\u00fck bir gaz devine sahip olan y\u0131ld\u0131z\u0131n 10 D\u00fcnya k\u00fctlesine denk gezegen yuttu\u011funu saptad\u0131lar. \u0130ki Nept\u00fcn boyunda gezegen sahibi olan y\u0131ld\u0131z\u0131n ise 20 D\u00fcnya k\u00fctlesine denk gezegen yuttu\u011funu ortaya \u00e7\u0131kard\u0131lar. Ancak yok olan gezegenlerin k\u00fctlesini bilmedikleri i\u00e7in, yamyam g\u00fcne\u015flerin ka\u00e7 gezegen yedi\u011fini tespit etmeleri m\u00fcmk\u00fcn olmad\u0131.<\/p>\n Neden bir y\u0131ld\u0131z di\u011ferinin iki kat\u0131 gezegen yuttu?<\/strong><\/span><\/p>\n Belki de obur y\u0131ld\u0131z\u0131n etraf\u0131nda iki kat fazla gezegen vard\u0131; ama bu durumda verece\u011fimiz en basit cevap ayn\u0131 zamanda yanl\u0131\u015f cevap olur: Yukar\u0131da anlatt\u0131\u011f\u0131m\u0131z sebeplerle, \u00e7ift y\u0131ld\u0131zlar\u0131n etraf\u0131nda \u00e7ok say\u0131da gezegen olamayaca\u011f\u0131n\u0131 biliyoruz. Bu durumda bir y\u0131ld\u0131z\u0131n di\u011ferinden iki kat fazla kayal\u0131k gezegene sahip olmas\u0131 zor g\u00f6r\u00fcn\u00fcyor.<\/p>\n \u00d6yleyse bu gizemi nas\u0131l a\u00e7\u0131klayabiliriz? \u00d6ncelikle biraz mant\u0131k y\u00fcr\u00fcterek: Her iki y\u0131ld\u0131z da ba\u015flang\u0131\u00e7ta az say\u0131da kayal\u0131k gezegene sahip olmal\u0131. Ancak bunlar\u0131n bir k\u0131sm\u0131 s\u00fcper d\u00fcnya s\u0131n\u0131f\u0131na giren ve Yery\u00fcz\u00fcnden iki kat k\u00fctleli olan b\u00fcy\u00fck kayal\u0131k gezegenler olmal\u0131. Belki 20 D\u00fcnya k\u00fctlesine denk gezegen yutan y\u0131ld\u0131z\u0131n \u00e7evresinde, iki kat olmasa da karde\u015finden daha fazla say\u0131da gezegen d\u00f6n\u00fcyordu. Bu a\u00e7\u0131klamay\u0131 kabul etti\u011fimiz zaman i\u015fimiz kolayla\u015f\u0131yor.<\/p>\n Bir elin nesi var?<\/strong><\/span><\/p>\n \u0130ki elin sesi var! Nept\u00fcn boyundaki 2 gezegenin toplam \u00e7ekim etkisi ve bunun yaratt\u0131\u011f\u0131 b\u00fcy\u00fck dengesizlik, kendi y\u0131ld\u0131zlar\u0131na daha fazla gezegenin d\u00fc\u015fmesine yol a\u00e7m\u0131\u015f olmal\u0131. K\u0131sacas\u0131 J\u00fcpiter b\u00fcy\u00fckl\u00fc\u011f\u00fcndeki gaz devi, iki k\u00fc\u00e7\u00fck gezegenin say\u0131 \u00fcst\u00fcnl\u00fc\u011f\u00fcne yenilmi\u015f ve y\u0131ld\u0131zlardan biri daha fazla gezegen t\u00fcketmi\u015f oluyor. Hatta Nept\u00fcn boyundaki iki gezegenden yararlanan obur g\u00fcne\u015f, karde\u015f y\u0131ld\u0131z\u0131n y\u00f6r\u00fcngesindeki kayal\u0131k gezegenlerden bir k\u0131sm\u0131n\u0131 \u00e7al\u0131p yemi\u015f olabilir.<\/p>\n Mack bu kozmik k\u0131yameti \u015f\u00f6yle a\u00e7\u0131kl\u0131yor: \u201cY\u0131ld\u0131z\u0131n ba\u015flang\u0131\u00e7ta D\u00fcnya benzeri kayal\u0131k gezegenler olu\u015fturdu\u011funu hayal edin. Ayr\u0131ca J\u00fcpiter gibi gaz devi gezegenler olu\u015fturdu\u011funu da d\u00fc\u015f\u00fcn\u00fcn. Kayal\u0131k gezegenler y\u0131ld\u0131za yak\u0131n s\u0131cak b\u00f6lgede ve gaz devleri de gezegen sisteminin so\u011fuk d\u0131\u015f kesimlerinde olu\u015fuyor. Ancak, gaz devleri olu\u015fumunu tamamlad\u0131ktan sonra i\u00e7 kesimlere do\u011fru g\u00f6\u00e7 ediyor ve bu s\u0131rada yer\u00e7ekimi etkisiyle i\u00e7 b\u00f6lgedeki kayal\u0131k gezegenleri \u00e7eki\u015ftirmeye ba\u015fl\u0131yor.\u201d<\/p>\n \u201cGaz devleri di\u011fer gezegenleri yeterince \u00e7eki\u015ftirirse, kayal\u0131k gezegenlerin y\u0131ld\u0131z\u0131n i\u00e7ine d\u00fc\u015fmesine neden olabilir. Y\u0131ld\u0131za yeterince kayal\u0131k gezegen d\u00fc\u015ferse, bunlar y\u0131ld\u0131z\u0131n atmosferinde teleskoplar\u0131m\u0131zla tespit edebilece\u011fimiz kadar belirgin bir kimyasal iz olu\u015fturacakt\u0131r.\u201d<\/p>\n D\u00fcnya benzeri hayat yayg\u0131n m\u0131, nadir mi?<\/strong><\/span><\/p>\n Bu mant\u0131\u011fa g\u00f6re nadir. Samanyolu Galaksisi\u2019ndeki y\u0131ld\u0131z sistemlerinin \u00fc\u00e7te birinin iki y\u0131ld\u0131z, \u00fc\u00e7 y\u0131ld\u0131z veya daha fazla say\u0131da y\u0131ld\u0131z bar\u0131nd\u0131ran sistemlerden olu\u015ftu\u011funu d\u00fc\u015f\u00fcn\u00fcrsek bunu anl\u0131yoruz.<\/p>\n \u00c7oklu y\u0131ld\u0131z sistemlerinde az say\u0131da gezegen var veya bu t\u00fcr sistemlerde az say\u0131da gezegen yamyam y\u0131ld\u0131zlardan kurtularak hayatta kal\u0131yor. Bu da uzayda D\u00fcnya benzeri hayat\u0131n san\u0131landan nadir oldu\u011fu anlam\u0131na geliyor.<\/p>\n Yine de bu sorunun cevab\u0131n\u0131 bilmiyoruz:<\/strong><\/span><\/p>\n Mack\u2019\u0131n ara\u015ft\u0131rd\u0131\u011f\u0131 \u00e7ift y\u0131ld\u0131z sistemindeki J\u00fcpiter benzeri gezegen, g\u00fcne\u015fine Merk\u00fcr\u2019den daha fazla yakla\u015f\u0131yor ve neredeyse y\u0131ld\u0131z\u0131 s\u0131y\u0131r\u0131p ge\u00e7iyor. Nept\u00fcn boyundaki di\u011fer iki gezegen ise y\u0131ld\u0131z\u0131na 50 milyon kilometre uzakta d\u00f6n\u00fcyor. Ancak as\u0131l espri, uzayda metal bak\u0131m\u0131ndan zengin sar\u0131 c\u00fcce y\u0131ld\u0131zlar\u0131n ne kadar yayg\u0131n oldu\u011funda yat\u0131yor.<\/p>\n Bug\u00fcne kadar galaksimizde G\u00fcne\u015f\u2019in ikizini bulamad\u0131k. G\u00fcne\u015f\u2019e benzeyen y\u0131ld\u0131zlar var ama G\u00fcne\u015f\u2019e \u00e7ok benzeyen sadece bir iki y\u0131ld\u0131z bulabildik ve bu y\u00fczden, hayat\u0131n be\u015fi\u011fi olan D\u00fcnyam\u0131z\u0131 \u0131s\u0131tan G\u00fcne\u015f\u2019in bile Evren\u2019de istisna olup olmad\u0131\u011f\u0131n\u0131 bilmiyoruz.<\/p>\n Dolay\u0131s\u0131yla uzayda D\u00fcnya benzeri gezegenlerin veya hayat\u0131n nadir olup olmad\u0131\u011f\u0131 hakk\u0131nda kesin bir \u015fey s\u00f6yleyemeyiz, \u00e7\u00fcnk\u00fc elimizde yeterli say\u0131da istatistiksel veri yok. Belki de yaz\u0131m\u0131zda anlatt\u0131\u011f\u0131m\u0131z \u00e7ift y\u0131ld\u0131z sisteminde ve di\u011fer \u00e7oklu y\u0131ld\u0131z sistemlerinde hayatta kalan ba\u015fka kayal\u0131k gezegenler var. Belki de teleskoplar\u0131m\u0131z\u0131n g\u00f6z\u00fc keskin olmad\u0131\u011f\u0131 i\u00e7in se\u00e7emiyoruz bunlar\u0131.<\/p>\n Uzay teleskoplar\u0131:<\/strong><\/span><\/p>\n Mack\u2019\u0131n g\u00f6zlemlerinden yola \u00e7\u0131karak, atmosferinde y\u00fcksek miktarda metal bulunan G\u00fcne\u015f benzeri sar\u0131 c\u00fccelerin kayal\u0131k gezegenlere sahip olma ihtimalinin d\u00fc\u015f\u00fck oldu\u011funu s\u00f6yleyebiliriz. Ancak kesin konu\u015fmak i\u00e7in daha fazla y\u0131ld\u0131z sistemini g\u00f6zlemlemek gerekiyor.<\/p>\n Sonu\u00e7 olarak Evren\u2019de d\u00fc\u015f\u00fck miktarda metal i\u00e7eren G\u00fcne\u015f benzeri sar\u0131 c\u00fcce y\u0131ld\u0131zlar\u0131n m\u0131, yoksa y\u00fcksek metal i\u00e7eren sar\u0131 c\u00fccelerin mi yayg\u0131n oldu\u011funu \u00f6\u011frenmenin tek yolu daha g\u00fc\u00e7l\u00fc teleskoplar in\u015fa etmek.<\/p>\n 2018 y\u0131l\u0131nda f\u0131rlat\u0131lacak olan James Webb Uzay Teleskopu, keskin g\u00f6zleriyle birka\u00e7 y\u00fcz \u0131\u015f\u0131k y\u0131l\u0131 uzakl\u0131ktaki en k\u00fc\u00e7\u00fck gezegenlerin bile resmini \u00e7ekerek bu sorunun cevab\u0131n\u0131 verebilir. En az\u0131ndan D\u00fcnya benzeri gezegenlerin say\u0131s\u0131n\u0131 yakla\u015f\u0131k olarak tahmin edebilmemiz i\u00e7in yeterli veri sa\u011flayabilir.<\/p>\n Her durumda, \u00f6nemli olan g\u00fcne\u015f sistemlerinde ortalama ka\u00e7 gezegen olu\u015ftu\u011funu bulmak de\u011fil. \u00d6nemli olan uzayda ka\u00e7 kayal\u0131k gezegenin hayatta kalmay\u0131 ba\u015fard\u0131\u011f\u0131n\u0131 bulmak. Buna hayat memat meselesi desek yeridir! : )<\/p>\n Al\u0131nt\u0131<\/p>\n <\/p>\n","protected":false},"excerpt":{"rendered":" Astronomi Hollywood korku filmlerine benzemez. Bilim bir ke\u015fif ve ayd\u0131nlanma maceras\u0131d\u0131r, ama Vanderbilt \u00dcniversitesi\u2019ndeki astronomlar\u0131n son ke\u015ffinin korku filmlerini and\u0131rd\u0131\u011f\u0131n\u0131 s\u00f6yleyebiliriz. \u00c7\u00fcnk\u00fc bilim adamlar\u0131 uzayda do\u011fan gen\u00e7 d\u00fcnyalar\u0131 yutan yamyam y\u0131ld\u0131zlar ke\u015ffettiler. HD 20781 ve HD 20782 adl\u0131 iki y\u0131ld\u0131z toplam 30 gezegeni yutarak yok etti. Anla\u015f\u0131lan, uzayda hayat aray\u0131\u015f\u0131nda \u00f6nemli olan \u015fey galaksimizde D\u00fcnya …<\/p>\n","protected":false},"author":1,"featured_media":338,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[22],"tags":[],"class_list":["post-336","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-astronomi"],"_links":{"self":[{"href":"http:\/\/kosmosmacerasi.com\/v1\/wp-json\/wp\/v2\/posts\/336","targetHints":{"allow":["GET"]}}],"collection":[{"href":"http:\/\/kosmosmacerasi.com\/v1\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"http:\/\/kosmosmacerasi.com\/v1\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"http:\/\/kosmosmacerasi.com\/v1\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"http:\/\/kosmosmacerasi.com\/v1\/wp-json\/wp\/v2\/comments?post=336"}],"version-history":[{"count":1,"href":"http:\/\/kosmosmacerasi.com\/v1\/wp-json\/wp\/v2\/posts\/336\/revisions"}],"predecessor-version":[{"id":339,"href":"http:\/\/kosmosmacerasi.com\/v1\/wp-json\/wp\/v2\/posts\/336\/revisions\/339"}],"wp:featuredmedia":[{"embeddable":true,"href":"http:\/\/kosmosmacerasi.com\/v1\/wp-json\/wp\/v2\/media\/338"}],"wp:attachment":[{"href":"http:\/\/kosmosmacerasi.com\/v1\/wp-json\/wp\/v2\/media?parent=336"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"http:\/\/kosmosmacerasi.com\/v1\/wp-json\/wp\/v2\/categories?post=336"},{"taxonomy":"post_tag","embeddable":true,"href":"http:\/\/kosmosmacerasi.com\/v1\/wp-json\/wp\/v2\/tags?post=336"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}