親子觀星會

https://technews.tw/2019/08/30/exomoon-exoplanet-wasp-49b-volcanic/

如果你想見識宇宙中有沒有一個表面佈滿熔融岩漿的地獄星球，那你可能不能錯過 WASP-49b 巨行星的系外衛星，環境比我們太陽系的木衛一還要更極端。

木衛一埃歐（Io）直徑約 3,642 公里，是太陽系木星衛星群中最靠近木星的一顆，因此受到木星強烈引力牽引而經歷劇烈潮汐加熱過程，使木衛一成為太陽系中火山活動最活躍的天體，地表擁有高達 400 座活火山，甚至有些火山噴發的灰燼可攀升到 500 公里高。

而在距離我們約 550 光年的 WASP-49 恆星系統有顆巨行星 WASP-49b，現在根據瑞士伯恩大學團隊從巨行星 WASP-49b 附近探測到的鈉氣體表明，這顆行星可能擁有一顆比木衛一還要更地獄的系外衛星
   => 離WASP-49b 巨行星 遠 ..
  。由於極端的火山爆發可能將鈉和鉀噴入太空（木衛一便常做這些事），加上研究團隊探測到的鈉氣體位置與行星距離又太遠，不太可能是從行星表面被行星風吹出來的物質，因此研究人員相信火山衛星才是 WASP-49b 行星周圍鈉氣體特徵的來源。

只不過，天文學家到目前為止都還沒有直接觀察到 WASP-49b 周圍存在衛星的證據，而且研究團隊也坦承，WASP-49b 周圍的電離氣體也可以解釋鈉的存在，科學家未來必須找到更多數據，以證明這些氣體是來自系外衛星。

如果以後檢測確認 WASP-49b 行星真的帶有一顆火山衛星，這將構成一幅奇妙的情景：火熱衛星圍繞著火熱巨行星旋轉，這顆巨行星又每 3 天就圍繞母恆星旋轉一圈，是在我們太陽系中看不到的緊湊天體系統。

如果你想對這顆衛星的地貌更有概念一些，那你可以參考一下《星際大戰》的穆斯塔法星。新論文將發表在《天文物理期刊》（The Astrophysical Journal）期刊，論文預印本可以先上《arXiv》網站閱覽。

一颗类似《星球大战》虚构星球“穆斯塔法星”的系外卫星可能隐藏在系外行星系统WASP-49b中。这是一个危险的熔岩世界，其距离地球约550光年。

https://www.cnbeta.com/articles/science/883979.htm

系外卫星是一种天然卫星，在系外行星周围依照闭合轨道做周期性运行。天文学家 非常肯定它们的存在，但他们还没有做出明确的探测。  在一项将在《天体物理学杂志》上发表的新研究中，伯尔尼大学的研究人员详细介绍了这颗新的候选系外卫星。在巨型系外行星WASP-49b附近探测到的钠气体表明，这颗卫星上可能存在大量火山活动，类似于木卫一 (Io)。

瑞士伯尔尼大学的博士后研究员Apurva Oza在一份新闻稿中表示，“中性钠气体离行星很远，不太可能仅靠行星风发射。”系外卫星“将是一个危险的火山世界，拥有熔化的熔岩表面......阿纳金·天行者对类似的地方非常熟悉。”

需要明确的是，研究人员还没有直接观察到WASP-49b周围的卫星。相反，他们发现暗示这样一个“火山世界”卫星可以以钠气体的形式被发现。 Oza的工作表明，大量火山爆发可能会将钠和钾喷入太空。研究人员在木卫一 (Io)周围观察到了类似的现象，这导致研究小组建议他们在WASP-49b周围看到的信号与“exo-Io”有关。

然而，Oza承认围绕WASP-49b的大环电离气体也可以解释检测到的钠气体的存在。“我们需要找到更多线索，”他说道。

穆斯塔法星（英語：Mustafar），是喬治·盧卡斯導演的著名科幻電影《星際大戰》中的一個虛構的星球。它被設定為一顆表面有幾百個火山和岩漿河的星球，大部分火山不斷爆發。在《星際大戰前傳III：西斯大帝的復仇》與《星際大戰外傳：俠盜一號》中出現。


https://zh.wikipedia.org/wiki/%E7%A9%86%E6%96%AF%E5%A1%94%E6%B3%95%E6%98%9F

https://astronomynow.com/2019/09/03/evidence-found-for-volcanic-extreme-io-exomoon/
(https://mk0astronomynow9oh6g.kinstacdn.com/wp-content/uploads/2019/09/090319_hotmoon.jpg)
An artist’s impression of a hot exomoon, similar to Jupiter’s volcanic moon Io, orbiting a gas giant in a short-period orbit. Image: Thibaut Roger/University of Bern

Possible Volcanic Exomoon orbiting WASP 49Ab

Planetary scientists believe that may have discovered a volcanically active exomoon orbiting a Jupiter-size gas giant exoplanet, WASP 49Ab, located over 600 light years from the Earth.

WASP 49 is a binary star system (A/B) located 635 light years (195 parsecs) distant in the constellation of Lepus the Hare (6h4m21.47357s, -16°57'55.1087") with an apparent magnitude of 11.35. The larger star of the binary is WASP 49A that is approximately the diameter and mass of our Sun, spectral type G6V, metallicity Fe/H Index) of -0.23 (59% the Sun's level), and surface temperature of 5,600°K (9,620°F/5,330°C vs the Sun's 5,772°K (9,930°F/5,499°C)), and an estimated age of 11.9 billion years (versus the Sun's age of 4.6 billion years). The smaller star of the binary, WASP 49B has approximately 34% the Sun's mass and s surface temperature of 3,454°K (5,758°F/3,181°C). The pair of stars are separated by 443 AU (41,199 million miles/66,299 million km).

WASP 49Ab is a Jupiter-sized gas giant exoplanet that was discovered by a team led by Monika Lendl (University of Geneva) in August, 2012 using the WASP CCD array by the primary transit method (decrease in the light curve of the star as the exoplanet crosses the star). WASP 49Ab is approximately 12 % larger than the planet Jupiter but with only 40% its mass (making it one of the lightest exoplanets discovered). It orbits the primary star (WASP 49) at an average distance of 0.0379 AU (~3.5 million miles/5.7 million km, or 4% the Earth-Sun distance) in a period of 2.8 days. The orbit of WASP 49Ab is inclined 85 degrees to its primary star. Its equilibrium temperature is 1,369°K (2,005°F/1,096°C) making it a "Hot Jupiter" and far within its habitable zone.

An extensive sodium (Na) cloud was discovered orbiting WASP 49Ab in 2017 by Apurva V. Oza (NASA JPL and now at Caltech). Both WASP-49 b and its star are composed mostly of hydrogen and helium, with trace amounts of sodium. Neither contains enough sodium to account for the cloud, which appears to be coming from a source that is producing roughly 220,000 pounds (100,000 kilograms) of sodium per second. Even if the star or planet could produce that much sodium, it’s unclear what mechanism could eject it into space. As detailed in a new study published in the Astrophysical Journal Letters, they found several pieces of evidence that suggest the cloud is created by a separate body orbiting the planet, though additional research is needed to confirm the cloud’s behavior. For example, twice their observations indicated the cloud suddenly increased in size, as if being refueled, when it was not next to the planet. They also observed the cloud moving faster than the planet in a way that would seem impossible unless it was being generated by another body moving independent of, and faster, than the planet. “We think this is a really critical piece of evidence,” said Oza. “The cloud is moving in the opposite direction that physics tells us it should be going if it were part of the planet’s atmosphere.” While these observations have intrigued the research team, they say they would need to observe the system for longer to be sure of the cloud’s orbit and structure.

https://astrobiology.com/2024/10/does-distant-planet-wasp-49-b-host-volcanic-moon-like-jupiters-io.html