G\u00fcne\u015f etraf\u0131nda, elips \u015feklinde bir y\u00f6r\u00fcnge\u00a0\u00e7izerek, d\u00f6nen g\u00f6k cisimlerine gezegen denir.\u00a0G\u00fcn\u00fcm\u00fczde gezegen denildi\u011fi zaman, ba\u015fta d\u00fcny\u00e2m\u0131z olmak \u00fczere, G\u00fcne\u015f etraf\u0131nda d\u00f6nen di\u011fer\u00a0sekiz gezegen akla gelmektedir. Fakat uzayda farkl\u0131 g\u00fcne\u015fler etr\u00e2f\u0131nda bir\u00e7ok gezegen bulunmaktad\u0131r.<\/p>\n
Sadece galaksimiz Samanyolu\u2019nda iki y\u00fcz milyar y\u0131ld\u0131z bulundu\u011funu g\u00f6z \u00f6n\u00fcne al\u0131rsak, bilinen t\u00fcm galaksilerde iki trilyona yak\u0131n gezegenin varl\u0131\u011f\u0131ndan s\u00f6z edilebilir. D\u00fcny\u00e2m\u0131z d\u00e2hil olmak \u00fczere G\u00fcne\u015f etraf\u0131nda\u00a0d\u00f6nen dokuz gezegen inceleyebildi\u011fimiz yeg\u00e2ne gezegenlerdir. Bu gezegenler uzayda parlayan\u00a0y\u0131ld\u0131zlardan kolayl\u0131kla ay\u0131rt edilebilir. \u015e\u00f6yle ki, gezegenlerin \u0131\u015f\u0131klar\u0131 y\u0131ld\u0131zlar gibi k\u0131rp\u0131\u015fmaz. I\u015f\u0131klar\u0131\u00a0atmosferden do\u011frudan do\u011fruya gelir. Sistemimizdeki gezegenlerin yo\u011funluklar\u0131, b\u00fcy\u00fckl\u00fcklerine g\u00f6re\u00a0de\u011fi\u015fmektedir. Buna g\u00f6re g\u00fcne\u015f sisteminde en az yo\u011fun gezegen Jupiter\u2019dir. Ger\u00e7ekten de bu\u00a0gezegen asl\u0131nda dev bir k\u0131zg\u0131n gaz k\u00fcresinden ba\u015fka bir\u015fey de\u011fildir.<\/p>\n
Gezegenlerin iki t\u00fcrl\u00fc hareketi\u00a0vard\u0131r. Bu g\u00f6k cisimleri hem kendi etraf\u0131nda hem de elips bi\u00e7imindeki bir y\u00f6r\u00fcngede, G\u00fcne\u015f\u2019in\u00a0etraf\u0131nda d\u00f6nerler. Bilindi\u011fi gibi gezegenler y\u0131ld\u0131zlar gibi \u0131\u015f\u0131k kayna\u011f\u0131 de\u011fildir. Onlar ancak G\u00fcne\u015f\u2019ten\u00a0ald\u0131klar\u0131 \u0131\u015f\u0131\u011f\u0131 yans\u0131t\u0131rlar.<\/p>\n
G\u00fcne\u015f sistemi ad\u0131 verilen dokuz gezegen, G\u00fcne\u015f\u2019ten uzakl\u0131klar\u0131 bak\u0131m\u0131nda s\u0131ras\u0131yla \u015funlard\u0131r: Merk\u00fcr, Ven\u00fcs,\u00a0D\u00fcny\u00e2, Mars, J\u00fcpiter, Sat\u00fcrn, Uran\u00fcs, Nept\u00fcn, Pl\u00fcton. Bunlardan G\u00fcne\u015f\u2019e en yak\u0131n \u00fc\u00e7 gezegen olan\u00a0Merk\u00fcr, Ven\u00fcs ve D\u00fcny\u00e2\u2019ya \u201c\u0130\u00e7 Gezegenler\u201d; Mars, J\u00fcpiter, Sat\u00fcrn, Uran\u00fcs, Nept\u00fcn ve Pl\u00fcton\u2019a \u201cD\u0131\u015f\u00a0Gezegenler\u201d ad\u0131 verilir. Bir de Mars ve Jupiter aras\u0131nda Asteroid ad\u0131 verilen minik gezegenler\u00a0bulunmaktad\u0131r. \u00d6te yandan Merk\u00fcr, Ven\u00fcs ve Pl\u00fcton h\u00e2ri\u00e7 b\u00fct\u00fcn gezegenlerin bir veya birka\u00e7 uydusu\u00a0bulunmaktad\u0131r.<\/p>\n