D\u00fcnya’dan 226 \u0131\u015f\u0131k y\u0131l\u0131 uzakta, D\u00fcnya’n\u0131n iki kat\u0131 b\u00fcy\u00fckl\u00fc\u011f\u00fcnde, y\u00fczeyinde su bar\u0131nd\u0131rd\u0131\u011f\u0131 d\u00fc\u015f\u00fcn\u00fclen bir \u00f6tegezegen ke\u015ffedildi. <\/p>\n
K2-288Bb olarak isimlendirilen yeni \u00f6tegezegenin yap\u0131s\u0131 D\u00fcnya gibi kayal\u0131k ya da Nept\u00fcn’e benzeyen gaz bak\u0131m\u0131ndan zengin bir gezegen yap\u0131s\u0131na sahip olabilir.<\/p>\n
Seattle\u2019daki Amerikan Astronomik Toplulu\u011fu\u2019nun 233. toplant\u0131s\u0131nda ke\u015ffi yapan \u015eikago \u00dcniversitesi y\u00fcksek lisans \u00f6\u011frencisi Adina Feinstein, \u201cBulunan bu \u00f6te gezegen, \u0131l\u0131man y\u00f6r\u00fcngesi ve bu boyuttaki gezegenlerin nispeten nadir g\u00f6r\u00fclmesi nedeniyle \u00e7ok heyecan verici bir ke\u015fif.\u201d dedi.<\/p>\n
Kepler uzay teleskobu 30 Ekim 2018’de yak\u0131t\u0131n\u0131n t\u00fckenmesi nedeniyle 9 y\u0131l s\u00fcren g\u00f6revini tamamlad\u0131. Kepler, G\u00fcne\u015f Sistemi d\u0131\u015f\u0131nda 2 bin 600 gezegen ke\u015ffetti. Bu ke\u015fifler sayesinde o zamana dek y\u0131ld\u0131zlar ve y\u0131ld\u0131z k\u00fcmelerinin odaklanan g\u00f6kbilimde \u00f6tegezegenler ba\u015fl\u0131 ba\u015f\u0131na bir ara\u015ft\u0131rma konusu haline geldi.<\/p>\n
Kepler’in ke\u015fifleri sayesinde g\u00f6ky\u00fcz\u00fcndeki y\u0131ld\u0131zlar\u0131n y\u00fczde 20’si ila y\u00fczde 50’sinin y\u00f6r\u00fcngesinde ya\u015fama elveri\u015fli D\u00fcnya’ya benzer boyutta kayal\u0131k gezegenler bar\u0131nd\u0131rd\u0131\u011f\u0131 anla\u015f\u0131ld\u0131.<\/p>\n
G\u00fcne\u015f d\u0131\u015f\u0131 gezegen ya da \u00f6tegezegen, G\u00fcne\u015f Sistemi’nin d\u0131\u015f\u0131nda ve ba\u015fka bir y\u0131ld\u0131z\u0131n y\u00f6r\u00fcngesinde bulunan gezegendir. 4 May\u0131s 2017 itibar\u0131 ile 3610 g\u00fcne\u015f \u00f6tesi gezegen (2704 gezegen sistemi, 610 \u00e7oklu gezegen sistemi) alg\u0131lanm\u0131\u015f ve do\u011frulanm\u0131\u015ft\u0131r.Bu gezegenlerin b\u00fcy\u00fck bir\u00e7o\u011funlu\u011fu fiili g\u00f6r\u00fcnt\u00fclemeden ziyade do\u011frudan olmayan \u00e7e\u015fitli y\u00f6ntemlerle saptand\u0131. Bunlar\u0131n \u00e7o\u011fu J\u00fcpiter’i and\u0131ran \u015fekilde b\u00fcy\u00fck k\u00fctleli dev gezegenlerdir, bununla birlikte muhtemelen bu alg\u0131lama teknolojisinin s\u0131n\u0131rl\u0131 olmas\u0131ndan kaynakl\u0131d\u0131r. Hen\u00fcz do\u011frulanmam\u0131\u015f yeni saptamalar daha k\u00fc\u00e7\u00fck d\u00fcnyalar\u0131n \u00e7ok daha yayg\u0131n oldu\u011fu fikrini veriyor.<\/p>\n
G\u00fcne\u015f d\u0131\u015f\u0131 gezegenler 19. y\u00fczy\u0131l\u0131n ortas\u0131nda bilimsel ara\u015ft\u0131rma konusu haline geldi. Astronomlar genellikle bu gezegenlerin var olduklar\u0131n\u0131 farzediyorlard\u0131 ancak ne kadar yayg\u0131n olduklar\u0131n\u0131 ya da G\u00fcne\u015f Sistemi’ndeki gezegenlerle ne derecede benzerlik g\u00f6sterdiklerini bilmiyorlard\u0131. Do\u011frulanm\u0131\u015f ilk ke\u015fif 1990’larda yap\u0131ld\u0131 ve 2000’den beri her y\u0131l 15’ten fazla yeni ke\u015fif yap\u0131ld\u0131. Ke\u015fif s\u0131kl\u0131\u011f\u0131 2007’de ke\u015ffedilen 67 gezegenle art\u0131\u015f g\u00f6sterdi. Tahminlere g\u00f6re g\u00fcne\u015f benzeri y\u0131ld\u0131zlar\u0131n en az %10’u gezegenlere sahip ve ger\u00e7ek oran \u00e7ok daha y\u00fcksek olabilir.<\/p>\n
G\u00fcne\u015f d\u0131\u015f\u0131 gezegenlerin ke\u015ffi d\u00fcnya d\u0131\u015f\u0131 ya\u015famla ilgili sorular\u0131 \u015fiddetlendirdi. \u015eu an i\u00e7in k\u0131rm\u0131z\u0131 c\u00fcce Gliese 581’in \u00fc\u00e7\u00fcnc\u00fc gezegeni ve y\u00f6r\u00fcngesi \u00e7evreledi\u011fi y\u0131ld\u0131z\u0131n ya\u015fanabilir bir b\u00f6lgesine yak\u0131n bulunan Gliese 581 d (D\u00fcnya’dan yakla\u015f\u0131k olarak 20 \u0131\u015f\u0131k y\u0131l\u0131 uzakl\u0131kta) hen\u00fcz ke\u015ffedilen muhtemel yerbenzeri gezegenlerin en iyi \u00f6rne\u011fi olarak g\u00f6r\u00fcn\u00fcyor. Bu kat\u0131 ko\u015fullardan gidilirse gezegenin konumu ya\u015fanabilir b\u00f6lgenin d\u0131\u015f\u0131nda g\u00f6r\u00fcn\u00fcyor, ancak sera etkisi gezegenin y\u00fczey s\u0131cakl\u0131\u011f\u0131n\u0131 y\u00fckselterek suyun varl\u0131\u011f\u0131n\u0131 destekleyebilir.<\/p>\n
Gezegenler y\u00f6r\u00fcngesinde doland\u0131klar\u0131 y\u0131ld\u0131zlara oranla olduk\u00e7a zay\u0131f \u0131\u015f\u0131k kaynaklar\u0131d\u0131r. G\u00f6r\u00fcn\u00fcr dalga boylar\u0131nda gezegenler y\u0131ld\u0131zlar\u0131n parlakl\u0131\u011f\u0131n\u0131n milyonda birinden daha az parlakl\u0131\u011fa sahiptir. Bu derece zay\u0131f bir \u0131\u015f\u0131k kayna\u011f\u0131n\u0131 tespit etmenin esas zorlu\u011funa ek olarak y\u0131ld\u0131z onu temizleyen bir parlakl\u0131\u011fa sebep olur.<\/p>\n
Bu sebeplerden dolay\u0131 \u015fimdiki teleskoplar sadece istisnai durumlarda do\u011frudan g\u00f6r\u00fcnt\u00fcleme yapabilirler. \u00d6zellikle gezegen b\u00fcy\u00fckse (J\u00fcpiter’den epeyce b\u00fcy\u00fckse), y\u00f6r\u00fcngesinde bulunan y\u0131ld\u0131za olduk\u00e7a mesafeliyse ve k\u0131z\u0131l\u00f6tesi \u0131\u015f\u0131n yay\u0131nlayabilecek kadar s\u0131caksa m\u00fcmk\u00fcn olabilir.<\/p>\n
Bilinen g\u00fcne\u015f sistemi d\u0131\u015f\u0131ndaki gezegenlerin \u00e7ok b\u00fcy\u00fck bir k\u0131sm\u0131 dolayl\u0131 y\u00f6ntemler yoluyla ke\u015ffedildi:<\/p>\n
G\u00f6k\u00f6l\u00e7\u00fcm (Astrometri): G\u00f6k\u00f6l\u00e7\u00fcm g\u00f6ky\u00fcz\u00fcndeki y\u0131ld\u0131zlar\u0131n konumlar\u0131n\u0131n kesin bir \u015fekilde \u00f6l\u00e7\u00fclmesi ve y\u0131ld\u0131z\u0131n zaman i\u00e7inde de\u011fi\u015fen konumlar\u0131yla olu\u015fan yollar\u0131n g\u00f6zlemlenmesini kapsar. E\u011fer y\u0131ld\u0131z\u0131n y\u00f6r\u00fcngesinde bir gezegen varsa, gezegenin k\u00fctle \u00e7ekimsel etkisi y\u0131ld\u0131z\u0131n kendi k\u00fctle merkezi etraf\u0131nda k\u00fc\u00e7\u00fck dairesel veya eliptik bir y\u00f6r\u00fcngede hareket etmesine sebep olacakt\u0131r (sa\u011fdaki animasyona bak\u0131n\u0131z).<\/p>\n
Radyal h\u0131z ve Doppler y\u00f6ntemi: Y\u0131ld\u0131z\u0131n D\u00fcnya’ya yakla\u015f\u0131rken veya uzakla\u015f\u0131rken sahip oldu\u011fu radyal h\u0131zdaki (y\u0131ld\u0131z\u0131n D\u00fcnya’ya g\u00f6re olan radyal h\u0131z\u0131) de\u011fi\u015fkenlikler y\u0131ld\u0131z\u0131n Doppler etkisi sebebiyle meydana gelen spektral \u00e7izgilerindeki yer de\u011fi\u015fiminden \u00e7\u0131kar\u0131labilir.[6] Bu a\u00e7\u0131k ara kullan\u0131lan en verimli y\u00f6ntemdir.<\/p>\n
Ge\u00e7i\u015f y\u00f6ntemi: E\u011fer bir gezegen y\u00f6r\u00fcngesinde bulunan y\u0131ld\u0131z\u0131n tekerinin \u00f6n\u00fcnden ge\u00e7erse y\u0131ld\u0131z\u0131n g\u00f6zlenen parlakl\u0131\u011f\u0131nda k\u00fc\u00e7\u00fck bir miktar d\u00fc\u015f\u00fc\u015f olur. Bu miktar gezegenin ve y\u0131ld\u0131z\u0131n boyutlar\u0131na ba\u011fl\u0131d\u0131r.<\/p>\n
K\u00fctle\u00e7ekimsel mikromercekleme: Mikromercekleme y\u0131ld\u0131z\u0131n gravitasyonel alan\u0131n\u0131n arkadaki y\u0131ld\u0131z\u0131n \u0131\u015f\u0131\u011f\u0131n\u0131 b\u00fckerek (mercek gibi) odaklamas\u0131yla meydana gelir. \u00d6ndeki y\u0131ld\u0131z\u0131n y\u00f6r\u00fcngesinde bulunan muhtemel bir gezegen mercekleme olay\u0131ndaki \u0131\u015f\u0131k e\u011frisinde alg\u0131lanabilecek anormalliklere sebep olabilir.<\/p>\n
G\u00fcne\u015f d\u0131\u015f\u0131 gezegenleri adland\u0131rman\u0131n en yayg\u0131n yolu, k\u00fc\u00e7\u00fck farklar d\u0131\u015f\u0131nda \u00e7ift y\u0131ld\u0131zlar\u0131nki ile benzerdir (y\u0131ld\u0131zlar i\u00e7in bir b\u00fcy\u00fck harf kullan\u0131l\u0131rken gezegenler i\u00e7in k\u00fc\u00e7\u00fck harf kullan\u0131l\u0131r). Y\u0131ld\u0131z\u0131n isminin sonuna sistemde bulunan birinci gezegen i\u00e7in “b” harfi kullan\u0131l\u0131r (51 Pegasi b). Sistemde bulunan bir sonraki gezegen alfabenin bir sonraki harfi ile i\u015faretlenir. \u00d6rne\u011fin 51 Pegasi \u00e7evresinde bulunan di\u011fer gezegen “51 Pegasi c” sonraki de “51 Pegasi d” adlar\u0131yla listelenebilir. E\u011fer iki gezegen ayn\u0131 zaman zarf\u0131nda ke\u015ffedilmi\u015fse y\u0131ld\u0131za en yak\u0131n olan\u0131 s\u0131radaki harfi al\u0131r. \u00d6rne\u011fin Gliese 876 sisteminde en son ke\u015ffedilen gezegen y\u0131ld\u0131za Gliese 876 b ve Gliese 876 c’den daha yak\u0131n olmas\u0131na ra\u011fmen Gliese 876 d ad\u0131yla an\u0131l\u0131r. 55 Cancri f gezegeni \u015fu anda ad\u0131nda “f” bulunan ilk ve tek gezegendir. \u015eimdilik “f”nin \u00f6tesinde kullan\u0131lan ba\u015fka bir harf yoktur.<\/p>\n
En bilinen G\u00fcne\u015f d\u0131\u015f\u0131 gezegenler kabaca G\u00fcne\u015f’e benzeyen F, G veya K spektral s\u0131n\u0131f\u0131ndaki anakol y\u0131ld\u0131zlar\u0131n\u0131n y\u00f6r\u00fcngesindedirler. Bu da basit\u00e7e gezegen ara\u015ft\u0131rma programlar\u0131n\u0131n bu t\u00fcr y\u0131ld\u0131zlar \u00fczerinde yo\u011funla\u015fmas\u0131n\u0131n sebeplerinden biridir. Ancak bu hesaba kat\u0131ld\u0131\u011f\u0131nda bile istatiksel analizler d\u00fc\u015f\u00fck k\u00fctleli y\u0131ld\u0131zlar\u0131n (M spektral s\u0131n\u0131f\u0131ndan k\u0131rm\u0131z\u0131 c\u00fcce) gezegene sahip olma ihtimalinin de d\u00fc\u015f\u00fck oldu\u011funu veya sahip olanlar\u0131n da gezegenleri daha d\u00fc\u015f\u00fck k\u00fctleye sahip olaca\u011f\u0131 i\u00e7in tespit edilmesinin zor olaca\u011f\u0131n\u0131 g\u00f6sterir. Spitzer Uzay Teleskobu taraf\u0131ndan yap\u0131lan son g\u00f6zlemler, “O” spektral s\u0131n\u0131f\u0131ndaki y\u0131ld\u0131zlar\u0131n G\u00fcne\u015f’ten \u00e7ok daha s\u0131cak oldu\u011funu ve photo-evaporation etkisine yol a\u00e7an bu \u00f6zelli\u011fin de gezegen olu\u015fumunu engelledi\u011fini g\u00f6steriyor.<\/p>\n
Y\u0131ld\u0131zlar ba\u015fl\u0131ca hidrojen ve helyum gibi hafif elementlerden olu\u015furlar. Ayr\u0131ca k\u00fc\u00e7\u00fck kesirlerde, demir gibi a\u011f\u0131r elementler i\u00e7erirler. Bu kesir miktar\u0131na y\u0131ld\u0131z\u0131n metalli\u011fi denir. Metalli\u011fi y\u00fcksek olan y\u0131ld\u0131zlar\u0131n gezegene sahip olma ihtimali daha y\u00fcksektir ve bunlar daha d\u00fc\u015f\u00fck metalli\u011fe sahip y\u0131ld\u0131zlara g\u00f6re daha fazla k\u00fctleye sahip olma e\u011filimindedir.<\/p>\n
Titiz spektral g\u00f6zlemlerde F2 s\u0131n\u0131f\u0131 y\u0131ld\u0131zlar\u0131ndan sonra d\u00f6nme h\u0131z\u0131n\u0131n aniden d\u00fc\u015ft\u00fc\u011f\u00fc bulundu. G\u00fcne\u015f’in G s\u0131n\u0131f\u0131ndan bir y\u0131ld\u0131z oldu\u011fu dikkate al\u0131nmal\u0131d\u0131r. G\u00fcne\u015f Sistemi’nin a\u00e7\u0131sal momentumunun y\u00fczde doksan sekizi gezegenlerin y\u00f6r\u00fcngesel hareketlerinden kaynaklan\u0131r. Yal\u0131t\u0131lm\u0131\u015f bir sistemde a\u00e7\u0131sal momentum ve tabii G\u00fcne\u015f’e ait y\u00fczde ikilik oran korunmal\u0131d\u0131r.<\/p>\n
\u0130lk gezegen aday\u0131 6 Ekim 1995 y\u0131l\u0131nda, 50 \u0131\u015f\u0131k y\u0131l\u0131 uza\u011f\u0131m\u0131zdaki 51 Pegasi y\u0131ld\u0131z\u0131n\u0131n \u00e7evresinde belirlendi. Ara\u015ft\u0131rmac\u0131lar, gezegenin yakla\u015f\u0131k J\u00fcpiter b\u00fcy\u00fckl\u00fc\u011f\u00fcnde, ama y\u0131ld\u0131z \u00e7evresindeki y\u00f6r\u00fcngesinin, bizim Merk\u00fcr’\u00fcn G\u00fcne\u015f’e olan uzakl\u0131\u011f\u0131ndan sekiz kat daha yak\u0131n oldu\u011funu belirlediler. Elbette bu yak\u0131nl\u0131ktaki bir gezegen, cehennem gibi s\u0131cak olmal\u0131d\u0131r. O g\u00fcnden bu yana ke\u015fefedilen yeni gezegenlerin say\u0131s\u0131 da h\u0131zla artt\u0131. Teleskoplar\u0131n ayna \u00e7aplar\u0131n\u0131n giderek artmas\u0131 ve milyonlarca y\u0131ld\u0131z\u0131n ayn\u0131 anda g\u00f6zlenmesini sa\u011flayan bilgisayar programlar\u0131 sayesinde son y\u0131llarda gezegen ke\u015fiflerinde bir patlama ya\u015fanm\u0131\u015ft\u0131r.<\/p>\n","protected":false},"excerpt":{"rendered":"
D\u00fcnya’dan 226 \u0131\u015f\u0131k y\u0131l\u0131 uzakta, D\u00fcnya’n\u0131n iki kat\u0131 b\u00fcy\u00fckl\u00fc\u011f\u00fcnde, y\u00fczeyinde su bar\u0131nd\u0131rd\u0131\u011f\u0131 d\u00fc\u015f\u00fcn\u00fclen bir \u00f6tegezegen ke\u015ffedildi. K2-288Bb olarak isimlendirilen yeni \u00f6tegezegenin yap\u0131s\u0131 D\u00fcnya gibi kayal\u0131k ya da Nept\u00fcn’e benzeyen gaz bak\u0131m\u0131ndan zengin bir gezegen yap\u0131s\u0131na sahip olabilir. Seattle\u2019daki Amerikan Astronomik Toplulu\u011fu\u2019nun 233. toplant\u0131s\u0131nda ke\u015ffi yapan \u015eikago \u00dcniversitesi y\u00fcksek lisans \u00f6\u011frencisi Adina Feinstein, \u201cBulunan bu \u00f6te […]<\/p>\n","protected":false},"author":23,"featured_media":0,"comment_status":"closed","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"_acf_changed":false,"inline_featured_image":false,"footnotes":""},"categories":[506],"tags":[],"class_list":["post-50159","post","type-post","status-publish","format-standard","hentry","category-astronomi"],"acf":[],"yoast_head":"\n