阋神星：修订间差异

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2005年7月30日 (六) 08:57的版本

File:2003 UB313 artist's impression.jpg

畫家筆下，於行星附近遠觀太陽的景象

2003 UB₃₁₃，又被稱為第十大行星及行星X，是一個外海王星天體，從推測所得，比冥王星為大。2003 UB₃₁₃由 Michael E. Brown 、 Chadwick A. Trujillo 和 David L. Rabinowitz 在2005年 1月8日，從一堆於2003年 10月21日拍攝的相片中發現，並在2005年 7月29日與2003 EL₆₁一起公佈。2003 UB₃₁₃於2005年7月位處於距離太陽97個天文單位遠的位置，而它的軌道極為傾斜，公轉周期為557年。它被分類為 scattered disk object。

發現

發現2003 UB₃₁₃的團隊，在以往幾年已有系統地找尋大形太陽系外天體。他們曾發現了另外數個外海王星天體，包括小行星50000(夸奧瓦)及小行星90377(塞德娜)。在2003年 10月31日，他們在美國加里福尼亞州帕洛瑪天文台的48英寸 Samuel Oschin 反射望遠鏡作例行觀察，但拍攝得來的影像，遲至2005年 1月，才從透過對比背景星空下，從它緩慢的移動中被發現。接著的觀察，初步找出它的軌道位置，以其估計它的直徑和大小。

軌道

2003 UB₃₁₃ 公轉周期約557年，於2005年7月位處於距離太陽97個天文單位遠的位置。像冥王星一樣，它的軌道離心率高，近日點為35個天文單位。 (冥王星距離太陽29至49.5天文單位；海王星則剛超過30天文單位。) 類地行星及類木行星的軌道平面與地球大致相等，而2003 UB₃₁₃的軌道平面則與黃道有約44度的傾側。

2003 UB₃₁₃的光度有視星等19，足以透過較新的望遠鏡觀察。因為它的軌道傾側，直至最近才被觀察到，而現時對太陽系的觀察，都集中了在黃道平面。

命名

根據小行星的命名常規，此星體的臨時命名2003 UB₃₁₃。因為此星體的重要性，相信很快會有正式命名。發現者有權決定它的名字，只要獲國際天文聯盟認可。從發現者的網站中，此小行星使用了 Lila 這名字 (取名自 Michael E. Brown 的女兒 Lilah) 。該發現團隊現時保留了此名字。 [1]

因為它的體積比冥王星大，它或會被考慮成為太陽系的第十大行星。媒體報導亦明示了這一點。但由於現時已發現了多個比冥王星大的天體，冥王星作為行星的看法再一次受到考驗。

大小

The brightness of a solar system object depends both on its size and the amount of light it reflects (its albedo). If the distance to an object and its albedo are both known, its radius can easily be determined from its apparent magnitude, with a higher albedo implying a smaller radius.

Currently, the albedo of 2003 UB₃₁₃ is not known, and so its true size cannot yet be determined. However, astronomers have calculated that even if it reflected all the light it receives (corresponding maximum albedo of 1.0), it would still have to be as large as Pluto. In fact, its albedo is likely to be much less than one, and so the object is likely to be somewhat larger than the planet. The object's maximum possible diameter is limited by the fact that it could not be detected by the Spitzer space telescope, suggesting that it must be less than 3000 km wide.

外部連結

MPEC listing for 2003 UB313
Astronomers Discover "10th Planet" - Sky & Telescope article
Slacker Astronomy Interview With Co-Discoverer Trujillo
Astronomers at Palomar Observatory Discover a 10th Planet Beyond Pluto - official webpage (yet to be updated)
Jet Propulsion Laboratory News Release
spaceflightnow.com
space.com

@@ 第8行： / 第8行： @@
 ==軌道==
+UB<sub>313</sub> 公轉周期約557年，於2005年7月位處於距離[[太陽]]97個[[天文單位]]遠的位置。像冥王星一樣，它的軌道[[離心率]]高，[[近日點]]為35個天文單位。 (冥王星距離太陽29至49.5天文單位；海王星則剛超過30天文單位。) [[類地行星]]及[[類木行星]]的軌道平面與地球大致相等，而2003 UB<sub>313</sub>的軌道平面則與[[黃道]]有約44度的傾側。
+UB<sub>313</sub>的光度有[[視星等]]19，足以透過較新的望遠鏡觀察。因為它的軌道傾側，直至最近才被觀察到，而現時對太陽系的觀察，都集中了在黃道平面。
-UB<sub>313</sub> has an [[orbital period]] of about 560 years, and currently lies about 97 astronomical units away from the Earth.  Like Pluto, its orbit is highly [[eccentricity|eccentric]], and brings it to within 35AU of the [[Sun]] at its [[perihelion]] (Pluto's distance from the Sun varies between 29 and 49.5AU, while Neptune orbits at just over 30AU).  Unlike the [[terrestrial planet]]s and [[gas giant]]s, whose orbits all lie roughly in the same [[plane]] as the Earth's, 2003 UB<sub>313</sub>'s orbit is inclined at an angle of about 44 [[degree (angle)|degrees]] to the [[ecliptic]].
-The new object is bright enough with an [[apparent magnitude]] of about 19 to be visible even in quite modest telescopes.  The inclination of its orbit is responsible for it going un-noticed until now, as most searches for large outer solar system objects concentrate on the ecliptic plane, in which most solar system material is found.
 ==命名==
+根據小行星的命名常規，此星體的臨時命名2003 UB<sub>313</sub>。因為此星體的重要性，相信很快會有正式命名。發現者有權決定它的名字，只要獲[[國際天文聯盟]]認可。從發現者的網站中，此小行星使用了 Lila 這名字 (取名自 Michael E. Brown 的女兒 Lilah) 。該發現團隊現時保留了此名字。 [http://www.gps.caltech.edu/~mbrown/planetlila/]
+因為它的體積比冥王星大，它或會被考慮成為[[太陽系]]的第十大行星。媒體報導亦明示了這一點。但由於現時已發現了多個比冥王星大的天體，冥王星作為[[行星]]的看法再一次受到考驗。
-The object currently has the [[provisional designation]] 2003 UB<sub>313</sub>, given according to the [[astronomical naming conventions]] for [[asteroid]]s.  Because of the object's importance, it is likely that it will receive an official name soon, which its discoverers have the right to choose, subject to the approval of the [[International Astronomical Union]].  The discovery web page uses the code name [[Lila]] (named after Michael Brown's newborn daughter, Lilah), though this is not the name the team has suggested to the IAU.   The team is withholding the suggested name at this time.  [http://www.gps.caltech.edu/~mbrown/planetlila/].
-As the object appears to be larger than [[Pluto]], it might come to be considered as the tenth planet in the [[Solar System]], and is already being accorded this status in media reports of its discovery.  However, as it is now well established that there are many objects of comparable size to Pluto in the outer solar system, the [[definition of planet|definition of the term 'planet']] may once again come into question.
 ==大小==
 The brightness of a solar system object depends both on its size and the amount of light it reflects (its [[albedo]]).  If the distance to an object and its albedo are both known, its [[radius]] can easily be determined from its apparent magnitude, with a higher albedo implying a smaller radius.