As our telescopes grow more powerful, astronomers are uncovering objects that defy conventional wisdom. The latest example is the discovery of a planet-like object circling a brown dwarf. It's the right size for a planet, estimated to be 5-10 times the mass of Jupiter. But the object formed in less than 1 million years -- the approximate age of the brown dwarf -- and much faster than the predicted time it takes to build planets according to some theories.
當我們的望遠鏡越來越強大，天文學家們就會揭開更多違反常理的物體的面紗。最新的例子是一顆被發現繞著褐矮星旋轉的行星般物體。它擁有一般行星的大小，估計質量約是木星的5-10倍。但它卻是在近100萬年間誕生的--大約跟那顆褐矮星年紀相同--這比理論上行星形成的時間要快上許多。
Kamen Todorov of Penn State University and co-investigators used the keen eyesight of the Hubble Space Telescope and the Gemini Observatory to directly image the companion of the brown dwarf, which was uncovered in a survey of 32 young brown dwarfs in the Taurus star-forming region. Brown dwarfs are objects that typically are tens of times the mass of Jupiter and are too small to sustain nuclear fusion to shine as stars do.
賓夕法尼亞州立大學的Kamen Todorov和同事們用哈伯望遠鏡的窄角視野觀察(ps1)，再配合雙子座天文台(ps2)對這顆伴星取得的直接影像來做研究(雙子座天文台已經在金牛座的恆星育成地區發現32顆年輕的褐矮星)。褐矮星通常是質量為木星數十倍的天體，但其質量依然不足以引發核心核融合而像一般星星一樣閃耀。
The mystery object orbits the nearby brown dwarf at a separation of approximately 2.25 billion miles (3.6 billion kilometers -- which is between the distances of Saturn and Uranus from the Sun). The team's research is being published in an upcoming issue of The Astrophysical Journal.
這顆神秘的天體環繞褐矮星的軌道約22.5億英里(36億公里--也就是以太陽系來說在土星和天王星之間)。這個團隊的研究將會公開於The Astrophysical Journal(一本期刊)的"即將發表"文章裡。
There has been a lot of discussion in the context of the Pluto debate over how small an object can be and still be called a planet. This new observation addresses the question at the other end of the size spectrum: How small can an object be and still be a brown dwarf rather than a planet? This new companion is within the range of masses observed for planets around stars -- less than 15 Jupiter masses. But should it be called a planet? The answer is strongly connected to the mechanism by which the companion most likely formed.
現在對於冥王星的辯論依然存在許多的討論:究竟一個天體可以到多小卻依然被稱為大行星(ps3)。這份新的觀測數據卻標出了這個問題的另一端:究竟一個天體可以到多小卻依然被稱為褐矮星而不是大行星？這顆新的伴星質量範圍所在是行星而非恆星--小於15倍木星質量。但應該叫它行星嗎?它形成的機構與卻又與一般伴星沒有兩樣。
There are three possible formation scenarios: Dust in a circumstellar disk slowly agglomerates to form a rocky planet 10 times larger than Earth, which then accumulates a large gaseous envelope; a lump of gas in the disk quickly collapses to form an object the size of a gas giant planet; or, rather than forming in a disk, a companion forms directly from the collapse of the vast cloud of gas and dust in the same manner as a star (or brown dwarf).
可能的形成原因有3種腳本:1.星周盤的塵埃慢慢的凝聚成約10倍地球大小的固態行星，這個行星更進一步蓄積了一層氣態的外殼；2.星周盤中的一塊氣體快速的塌陷組成一顆巨型氣態行星。3.雲氣並不維持盤狀，一顆伴星直接從雲氣中重力塌縮形成，就像一般恆星或褐矮星形成過程一樣。
If the last scenario is correct, then this discovery demonstrates that planetary-mass bodies can be made through the same mechanism that builds stars. This is the likely solution because the companion is too young to have formed by the first scenario, which is very slow. The second mechanism occurs rapidly, but the disk around the central brown dwarf probably did not contain enough material to make an object with a mass of 5-10 Jupiter masses.
若第3種是對的，那這個發現就表示了行星大小的天體也可以藉由恆星機制形成。這個推論最有可能是因為以第一種推輪來說，這顆伴星太年輕了。而第二種推論固然過程很快，但褐矮星周圍的雲氣似乎不足以形成5-10倍木星質量的天體。
"The most interesting implication of this result is that it shows that the process that makes binary stars extends all the way down to planetary masses. So it appears that nature is able to make planetary-mass companions through two very different mechanisms," says team member Kevin Luhman of the Center for Exoplanets and Habitable Worlds at Penn State University. If the mystery companion formed through cloud collapse and fragmentation, as stellar binary systems do, then it is not a planet by definition because planets build up inside disks.
"這個結論最有意思的地方是他說明了一件事，雙星系統的形成過程可以延伸到行星質量大小的範圍。所以大自然可以用兩種完全不同的方法做出一顆行星質量的天體。"Kelvin Luhman這樣說到，Luhman是Center for Exoplanets and Habitable Worlds at Penn State University的團隊成員之一。若這顆神秘的變星真的是從雲氣中塌陷而成，就像雙星系統一樣，那它就不是一顆從星周盤中被做出來的普通行星。(ps4)
The mass of the companion is estimated by comparing its brightness to the luminosities predicted by theoretical evolutionary models for objects at various masses for an age of 1 millon years.
這顆伴星的質量是由比較它的亮度在理論進化模型中"100萬年的天體"大致質量而推論出來的。(psX)
Further supporting evidence comes from the presence of a very nearby binary system that contains a small red star and a brown dwarf. Luhman thinks that all four objects may have formed in the same cloud collapse, making this in actuality a quadruple system. "The configuration closely resembles quadruple star systems, suggesting that all of its components formed like stars," says Luhman.
更多支持的證據來自於相當靠近的另一個雙星系統，這個雙星系統擁有一顆紅色星星和一顆褐矮星(ps5)。Luhman認為這4顆天體(這兩組雙星)可能是同一個雲氣塌陷而成，其實是一組四星系統。"這個構造相當像是四星系統，因為它的成員們都像恆星一般組成。"Luhman這麼說到。
ps1:窄域觀測可以明辨目標，廣域觀測則是尋找彼此間的關連或大致搜索。
ps2:這個天文台有2組8.1米望遠鏡
ps3:現今大行星定義為1.環繞太陽運行之天體
2.質量必須大到足以支持自身結構剛體強度，使球體維持靜態平衡的外型(近乎球體)
3.有能力清除軌道鄰近區域中的物質
冥王星因為沒有第三點的能力，而與穀神星(Ceres)、齊娜(2003 UB313)並列為太陽系之"矮行星"
ps4:一般行星形成是中心恆星形成後，其恆星風吹拂週遭雲氣，促使行星誕生。
ps5:恆星質量較小，在主序帶時就會偏向紅色。所以這裡一顆紅星、一顆褐矮星組成的雙星系統也就代表由是兩顆小質量星體所組成。
psX:若它真是只有5-10倍的木星質量星體，何來Luminosity可以被比較?
當我們的望遠鏡越來越強大，天文學家們就會揭開更多違反常理的物體的面紗。最新的例子是一顆被發現繞著褐矮星旋轉的行星般物體。它擁有一般行星的大小，估計質量約是木星的5-10倍。但它卻是在近100萬年間誕生的--大約跟那顆褐矮星年紀相同--這比理論上行星形成的時間要快上許多。
Kamen Todorov of Penn State University and co-investigators used the keen eyesight of the Hubble Space Telescope and the Gemini Observatory to directly image the companion of the brown dwarf, which was uncovered in a survey of 32 young brown dwarfs in the Taurus star-forming region. Brown dwarfs are objects that typically are tens of times the mass of Jupiter and are too small to sustain nuclear fusion to shine as stars do.
賓夕法尼亞州立大學的Kamen Todorov和同事們用哈伯望遠鏡的窄角視野觀察(ps1)，再配合雙子座天文台(ps2)對這顆伴星取得的直接影像來做研究(雙子座天文台已經在金牛座的恆星育成地區發現32顆年輕的褐矮星)。褐矮星通常是質量為木星數十倍的天體，但其質量依然不足以引發核心核融合而像一般星星一樣閃耀。
The mystery object orbits the nearby brown dwarf at a separation of approximately 2.25 billion miles (3.6 billion kilometers -- which is between the distances of Saturn and Uranus from the Sun). The team's research is being published in an upcoming issue of The Astrophysical Journal.
這顆神秘的天體環繞褐矮星的軌道約22.5億英里(36億公里--也就是以太陽系來說在土星和天王星之間)。這個團隊的研究將會公開於The Astrophysical Journal(一本期刊)的"即將發表"文章裡。
There has been a lot of discussion in the context of the Pluto debate over how small an object can be and still be called a planet. This new observation addresses the question at the other end of the size spectrum: How small can an object be and still be a brown dwarf rather than a planet? This new companion is within the range of masses observed for planets around stars -- less than 15 Jupiter masses. But should it be called a planet? The answer is strongly connected to the mechanism by which the companion most likely formed.
現在對於冥王星的辯論依然存在許多的討論:究竟一個天體可以到多小卻依然被稱為大行星(ps3)。這份新的觀測數據卻標出了這個問題的另一端:究竟一個天體可以到多小卻依然被稱為褐矮星而不是大行星？這顆新的伴星質量範圍所在是行星而非恆星--小於15倍木星質量。但應該叫它行星嗎?它形成的機構與卻又與一般伴星沒有兩樣。
There are three possible formation scenarios: Dust in a circumstellar disk slowly agglomerates to form a rocky planet 10 times larger than Earth, which then accumulates a large gaseous envelope; a lump of gas in the disk quickly collapses to form an object the size of a gas giant planet; or, rather than forming in a disk, a companion forms directly from the collapse of the vast cloud of gas and dust in the same manner as a star (or brown dwarf).
可能的形成原因有3種腳本:1.星周盤的塵埃慢慢的凝聚成約10倍地球大小的固態行星，這個行星更進一步蓄積了一層氣態的外殼；2.星周盤中的一塊氣體快速的塌陷組成一顆巨型氣態行星。3.雲氣並不維持盤狀，一顆伴星直接從雲氣中重力塌縮形成，就像一般恆星或褐矮星形成過程一樣。
If the last scenario is correct, then this discovery demonstrates that planetary-mass bodies can be made through the same mechanism that builds stars. This is the likely solution because the companion is too young to have formed by the first scenario, which is very slow. The second mechanism occurs rapidly, but the disk around the central brown dwarf probably did not contain enough material to make an object with a mass of 5-10 Jupiter masses.
若第3種是對的，那這個發現就表示了行星大小的天體也可以藉由恆星機制形成。這個推論最有可能是因為以第一種推輪來說，這顆伴星太年輕了。而第二種推論固然過程很快，但褐矮星周圍的雲氣似乎不足以形成5-10倍木星質量的天體。
"The most interesting implication of this result is that it shows that the process that makes binary stars extends all the way down to planetary masses. So it appears that nature is able to make planetary-mass companions through two very different mechanisms," says team member Kevin Luhman of the Center for Exoplanets and Habitable Worlds at Penn State University. If the mystery companion formed through cloud collapse and fragmentation, as stellar binary systems do, then it is not a planet by definition because planets build up inside disks.
"這個結論最有意思的地方是他說明了一件事，雙星系統的形成過程可以延伸到行星質量大小的範圍。所以大自然可以用兩種完全不同的方法做出一顆行星質量的天體。"Kelvin Luhman這樣說到，Luhman是Center for Exoplanets and Habitable Worlds at Penn State University的團隊成員之一。若這顆神秘的變星真的是從雲氣中塌陷而成，就像雙星系統一樣，那它就不是一顆從星周盤中被做出來的普通行星。(ps4)
The mass of the companion is estimated by comparing its brightness to the luminosities predicted by theoretical evolutionary models for objects at various masses for an age of 1 millon years.
這顆伴星的質量是由比較它的亮度在理論進化模型中"100萬年的天體"大致質量而推論出來的。(psX)
Further supporting evidence comes from the presence of a very nearby binary system that contains a small red star and a brown dwarf. Luhman thinks that all four objects may have formed in the same cloud collapse, making this in actuality a quadruple system. "The configuration closely resembles quadruple star systems, suggesting that all of its components formed like stars," says Luhman.
更多支持的證據來自於相當靠近的另一個雙星系統，這個雙星系統擁有一顆紅色星星和一顆褐矮星(ps5)。Luhman認為這4顆天體(這兩組雙星)可能是同一個雲氣塌陷而成，其實是一組四星系統。"這個構造相當像是四星系統，因為它的成員們都像恆星一般組成。"Luhman這麼說到。
ps1:窄域觀測可以明辨目標，廣域觀測則是尋找彼此間的關連或大致搜索。
ps2:這個天文台有2組8.1米望遠鏡
ps3:現今大行星定義為1.環繞太陽運行之天體
2.質量必須大到足以支持自身結構剛體強度，使球體維持靜態平衡的外型(近乎球體)
3.有能力清除軌道鄰近區域中的物質
冥王星因為沒有第三點的能力，而與穀神星(Ceres)、齊娜(2003 UB313)並列為太陽系之"矮行星"
ps4:一般行星形成是中心恆星形成後，其恆星風吹拂週遭雲氣，促使行星誕生。
ps5:恆星質量較小，在主序帶時就會偏向紅色。所以這裡一顆紅星、一顆褐矮星組成的雙星系統也就代表由是兩顆小質量星體所組成。
psX:若它真是只有5-10倍的木星質量星體，何來Luminosity可以被比較?
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