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ASTRONOMİ Terimleri

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ASTRONOMİ Terimleri A tayf türü yıldızlar (Alm. Sterne von Typ A, pl; Fr. étoiles de type A, pl; İng. A type stars) ast. Etkin sıcaklıkları 7.500 ile 10.000 K, anakolda olanların kütlesi 1,6 ile 2,5 Güneş kütlesi aralığında olan, tayflarında güçlü hidrojen ve iyonlaşmış ağır element çizgileri görülen açık mavi yıldızlar. aa indeksi (Alm. aa Index, m; Fr. indice aa; İng. aa index) ast. Yaklaşık zıt kutuplarda 50 derece enlemlerinde bulunan iki istasyondan elde edilen K jeomanyetik aktivite indisinden hesaplanan günlük ya da yarım günlük jeomanyetik aktivite indeksi. Abell kataloğu (Alm. Abell-Katalog, m; Fr. catalogue Abell, m; İng. Abell catalogue) ast. 1958 yılında George O. Abell tarafından yayınlanan, 2712 yakın gökada kümesini içeren, her bir kümenin en az 50 gökada içermesi, Abell yarıçapı içinde bulunacak kadar derlitoplu olmaları, 33 ile 330 megaparsek arasındaki uzaklıklarda bulunmaları gibi kriterleri sağlayan gökadalar kataloğu. Abell yarıçapı (Alm. Abell-Radius, m; Fr. rayon d'Abel, m; İng. Abell radius) ast. Abell kataloğundaki gökada kümelerinden hareketle, uzunluğu 2,14 megaparsek kabul edilen, tipik bir gökada kümesinin yarıçapı. açık evren (Alm. offenes Universum, n; Fr. univers ouvert, m; İng. open universe) ast. Ortalama madde yoğunluğunun kritik madde yoğunluğuna oranı birden küçük olduğunda, uzayın geometrik şeklinin bir eyer yüzeyi gibi açık olduğunu, bir üçgenin iç açılarının toplamının 180 dereceden küçük olduğunu, kesişmeyen doğruların her noktada eşit uzaklıkta olmadıklarını, evrenin hiperbolik şekilde olduğunu öngören evren modeli. açık yıldız kümesi (Alm. galaktischer Haufen, m; offener Sternhaufen, m; Fr. amas galactique ouvert, m; amas ouvert, m; İng. galactic cluster; open cluster) ast. Birbirlerine kütleçekim kuvveti ile zayıfça bağlı bir kaç on ila bir kaç yüz genç yıldızdan oluşan topluluk. açık yörünge (Alm. offene Bahn, f; Fr. trajectoire ouverte; İng. open orbit) ast. Yörünge dışmerkezliğinin 1 ya da 1’den büyük, yani yörüngedeki çizgisel hızın kurtulma hızına eşit ya da kurtulma hızından büyük olduğu parabolik ya da hiperbolik Kepler yörüngesi. açısal uzaklık (Alm. Winkelabstand, m; Fr. distance angulaire, f; écart angulaire, m; İng. angular distance; angular separation) 1. ast. İki yıldız gibi iki cismin arasındaki, derece, yay dakikası veya yay saniyesi cinsinden ifade edilen görünür uzaklık. 2. fiz. İki cismi gözlemciye birleştiren doğrular arasındaki açı. adyabatik atmosfer (Alm. adiabatische Atmosphäre, f; Fr. atmosphère adiabatique, f; İng. adiabatic atmosphere) ast. Havanın ısı iletkenliğinin çok düşük olmasından dolayı herhangi bir hava parçasının çevresiyle ısı alışverişinde bulunmayacağı, hava parçasının yükselmesi ile basıncın azalması ve hacminin genişlemesi sonucu sıcaklığının düşeceğini öngören, birinci mertebeden bir atmosfer modeli. adyabatik denge (Alm. adiabatisches Gleichgewicht, n; konvektives Gleichgewicht, n; Fr. équilibre adiabatique, m; équilibre convectif, m; İng. adiabatic equilibrium; convective equilibrium) ast. Bir sistemin sınırlarından ısı akışının gerçekleşmediği ya da giren ısının çıkan ısıya eşit olduğu denge durumu. adyabatik işlem (Alm. adiabater Prozess, m; adiabatischer Vorgang, m; Fr. processus adiabatique, m; İng. adiabatic process) ast. Çevresiyle ısı alışverişinin bulunmadığı kimyasal veya fiziksel süreç. adyabatik sıcaklık gradyanı (Alm. adiabatischer Temperaturgradient, m; Fr. gradient de température adiabatique, m; İng. adiabatic temperature gradient) ast. Adyabatik koşulların geçerli olduğu durumlarda, ortamdaki iki nokta arasındaki sıcaklık farkı. adyabatik soğuma (Alm. dynamische Abkühlung; adiabatische Abkühlung, f; Fr. refroidissement dynamique, m; refroidissiment adiabatique, m; İng. adiabatic cooling; dynamic cooling) ast. Adyabatik atmosferde, bir hava paketinin daha düşük basınçlı üst seviyeye ulaştığında genleşerek enerjisini harcaması ve sonuçta iç ısısını boşaltması. AE indeksi (Alm. AE-Index, m; Fr. indice AE, m; İng. AE index) ast. Güneşin doğuşu sırasında üst atmosferde iyonlaşmış bir tabakada, genel olarak güneş etkisiyle hareket eden elektrik yüklü akıntıyı belirleyen indeks. ağır element yıldızı (Fr. étoile à métaux lourdes, f; İng. heavy-metal star) ast. Tayfında baryum ve zirkonyum gibi ağır elementlerin çok kuvvetli çizgilerini gösteren, sıradışı ağır element bolluğuna sahip tuhaf dev yıldız. Ahernar (Alm. Achernar, m; alpha Eridani, m; Fr. Achernar, f; Alpha Eridani, f; İng. Achernar; Alpha Eridani) ast. Irmak Takımyıldızı’nın en parlak, 0,46 kadirlik parlaklığı ile gökyüzünün onuncu en parlak cismi olan, ortalama sıcaklığı 15.000 K ve yaklaşık uzaklığı 140 ışıkyılı tahmin edilen mavi yıldız; eşanlam: Ağız. akışlı tarama (Fr. en mode balayage; İng. drift scan) ast. Dünya'nın dönme hareketinden yararlanılarak gök cisimlerinin sabit bir teleskopun önünden geçirilerek görüntülenmesi; eşanlam: kaydırmalı tarama. Akrep Takımyıldızı (Alm. Scorpion, m; Fr. constellation du Scorpion, f; Scorpion, m; İng. Scorpius) ast. Gökkürede ekliptik düzlemi üzerinde yer alan, en parlak yıldızı Antares olan takımyıldız. Akrepyüreği (Alm. α Scorpii; Antares, m; Fr. α Scorpii; Antarès, f; İng. Alpha Scorpii; Antares) ast. Akrep (Scorpii) takımyıldızının en parlak yıldızı olup Güneş’e yaklaşık 600 ışıkyılı uzaklıkta, kadiri 0,6-1,6 arasında değişen kırmızı süper dev yıldız; eşanlam: Antares, Alfa Scorpii. aktif bölge (Alm. aktives Gebiet, n; Fr. région active, f; İng. active region) ast. Güneş yüzeyinde, güneş lekesi içeren veya içermeyen, civarından daha yoğun, sıcak, parlak olarak görülen, bir döngü oluşturan çift kutuplu manyetik bölge; eşanlam: aktif güneş bölgesi. aktif gökada (Alm. aktive Galaxie, f; Fr. galaxie active; İng. active galaxy) ast. Bir aktif çekirdek barındıran gökada. aktif gökada çekirdeği (Alm. aktiver galaktischer Kern, m; aktiver Galaxienkern, m; Fr. noyau actif de galaxie, m; İng. active galactic nucleus) ast. Kimi gökadaların merkezindeki, bir dev kara deliğin üzerine düşen maddenin yığılma diskine katılma sürecinde kaybettiği potansiyel enerjinin ışıma enerjisine dönüştüğü ve gökada ışımasının çoğunun kaynaklandığı bölge. aktif güneş uzantısı (Alm. aktive Protuberanz, f; Fr. protubérance active, f; protubérance solaire active, f; İng. active solar prominence) ast. Hızlı bir şekilde oluşan, Güneş atmosferinde dakikalarla saatler mertebesinde kalan, güneş lekeleri sayıları ile orantılı görülen, çevresine göre daha koyu görünen yüzeyden taca püsküren gaz yapısı. Akyıldız (Alm. α Canis Majoris; Aschere, f; Hundsstern, m; Sirius, m; Fr. Alpha Canis Majoris; Sirius, f; İng. Alpha Canis Majoris; Dog Star; Sirius) ast. -1.46 kadir parlaklığı ile gökyüzündeki en parlak cisim olan, yaklaşık uzaklığı 8,6 ışıkyılı olup Güneş’e en yakın beşinci sırada bulunan, Büyük Köpek Takımyıldızı’nda yer alan bir A1 cücesi; eşanlam: Sirius. Al Velorum yıldızı (Alm. Al Velorum, m; Fr. Al Velorum, f; İng. Al Velorum star) ast. Samanyolu’ndaki Yelken (Vela) Takımyıldızı’nın üyesi, periyodu 0,25 günden daha kısa ve genliği 0,3-1,2 kadir aralığında, Delta Scuti tipine benzeyen, atımlı değişen bir örten yıldız. alan merceği (Alm. Feldlinse, f; Kollektivlinse, f; Fr. lentille de champ, f; İng. collective lens; field lens) ast. Birden çok mercek içeren bir optik sistemde, objektif merceğinden daha sonra ama göz merceğinden daha önde yer alan, imgenin boyutlarını değiştirmekte ve eğriliklerini düzeltmekte kullanılan mercek. alan yıldızı (Alm. Feldstern, m; Fr. champ d'étoiles, m; İng. field star) ast. Herhangi bir yıldız kümesinin üyesi olmayan, Güneş gibi yıldızlardan her biri. alevli çift şerit (Alm. 2-Band Sonneneruption, f; Fr. éruption à filets parallèles, f; İng. two-ribbon flare) ast. Güneş'in manyetik alanındaki terselme hattının iki tarafında gelişen parlak bir çift alev kordonu. alfa Centauri (Alm. Alpha Centauri; Rigil Kentaurus; α Centauri; Fr. Alpha Centauri; Alpha du Centaure; α Centauri; İng. alpha Centauri) ast. 4,3 ışıkyılı uzaklıkta, Güneş’e en yakın üçlü yıldız sistemi; büyüklükleri Güneş’e çok yakın olan bu yıldızlardan Yakın Centauri ve alfa Centauri B gezegen barındırmaktadır. alfa elementleri (Alm. Elemente Alpha, pl; Fr. éléments alpha, pl; İng. alpha-elements; alpha-process elements) ast. ) Atom ağırlığı helyumun atom ağırlığı dördün katları olan, Tip II süpernova patlaması yapacak yıldızların nükleer özeğinde üretilen ve evrenin erken döneminde demire göre daha bol olan, C, O, Ne, Mg, Si, S, Ar ve Ca elementlerinin tümü; bazı araştırmacılar C ve O'i alfa elementleri arasında saymazlar. alfa etkisi (Alm. Alpha-Effekt, m; Fr. effet alpha, m; İng. alpha effect) 1. ast. Dönen astrofiziksel akışkanlarda konvektif türbülanstan ileri gelen, manyetik akı üretimine yol açan etki. 2. fiz. Bir yalın elektron çiftine sahip olan komşu bir atomun (alfa atomu) etkisiyle bir nükleofilin tepkinliğindeki artış. Alfa Haçı (Alm. Acrux, m; Alpha Crucis, m; Fr. Acrux, f; Alpha Crucis, f; İng. Acrux; Alpha Crucis) ast. Güneyhaçı Takımyıldızı’nın en parlak üyesi, 0,8 kadir parlaklığı ile çıplak gözle görülebilen, görünür tayf bandında ışıma gücü Güneş ışıma gücünün 25.000 katı olarak gökyüzünün 13. en parlak yıldızı olan, 320 ışıkyılı uzaklıkta, tek bir yıldız olarak görülse de aslında çoklu bir yıldız sistemi olan, mavi renkte B0, 5IV tayf tipinde bir alt dev; eşanlam: Alpha Crucis. Alfvén dalgası (Alm. Alfvénwelle, f; Fr. onde d’Alfvén, f; İng. Alfvén wave) ast. Manyetik plazmada, manyetik alanlarla elektrik akımlarının etkileşimi sonucu iyonların salınımı şeklinde ortaya çıkan, hızlarındaki düzensiz değişimlerin manyetik alandaki değişimleri izlediği, uzun dalga
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