圖1. 微類星體SS 433(背景)以162天的週期擺動。大約1百光年外，不顯眼的費米J1913 + 0515氣體雲(前景)，以相同的節奏跳動，暗示一種直接關聯性。不過，該微類星體確切如何驅動此氣體雲的‘悸動’， 仍然令人困惑。
Scientists have detected a mysterious gamma-ray heartbeat coming from a cosmic gas cloud. The inconspicuous cloud in the constellation Aquila is beating with the rhythm of a neighboring precessing black hole, indicating a connection between the two objects, as the team led by DESY Humboldt Fellow Jian Li and ICREA Professor Diego F. Torres from the Institute of Space Sciences (IEEC-CSIC) reports in the journal Nature Astronomy. Just how the black hole powers the cloud’s gamma-ray heartbeat over a distance of about 100 light years remains enigmatic.
科學家們已經發現一種，來自一處宇宙氣體雲之神秘γ-射線的悸動。該在天鷹星座中，不顯眼的氣體雲，如同由DESY Humboldt特別研究員Jian Li及西班牙太空科學研究所教授Diego F. Torres領導的團隊，於《自然•天文學》期刊記述的，正隨著鄰近一個進動(旋轉物體之旋轉軸又繞著另一軸旋轉的現象)之黑洞的律動跳動，顯示了這兩天體間的一種關聯性。只是在大約1百光年距離外，該黑洞如何驅動此氣體雲之γ-射線的悸動，仍然令人困惑。
進動段片：https://upload.wikimedia.org/wikipedia/commons/thumb/8/82/Gyroscope_precession.gif/220px-Gyroscope_precession.gif
The research team, comprising scientists from Germany, Spain, China and the U.S., rigorously analyzed more than ten years of data from the US space administration NASA’s Fermi gamma-ray space telescope, looking at a so-called micro quasar.
該由來自德國、西班牙、中國及美國科學家們組成的團隊縝密分析了，來自美國航太總署所屬費米γ-射線太空望遠鏡多於十年的數據，來探究一顆所謂的微類星體(類星體是一個極度明亮的活躍星系核，其中有個質量為數百萬到數十億倍太陽的超大質量黑洞，被氣體吸積盤所圍繞)。
The system cataloged as SS 433 is located some 15000 lightyears away in the Milky Way and consists of a giant star with about 30 times the mass of our sun and a black hole with about 10 to 20 solar masses. The two objects are orbiting each other with a period of 13 days, while the black hole sucks matter from the giant star.
該被編目為SS 433的系(指根據自然規律組成一個整體的天體群)座落於銀河系中，1萬5千光年外，且由一顆具有大約30倍咱們太陽質量的巨大恆星，及一個具有大約10到20個太陽質量的黑洞組成。這兩天體互相以13天的週期作繞軌運行，不過此黑洞從該巨大恆星吸取物質。
“This material accumulates in an accretion disc before falling into the black hole, like water in the whirl above the drain of a bathtub,” explains Li. “However, a part of that matter does not fall down the drain but shoots out at high speed in two narrow jets in opposite directions above and below the rotating accretion disk.”
Li解釋：「上述物質在落入黑洞之前，積聚於一個吸積盤中。就如同於浴缸排水口上方之旋渦中的水。不過，部分那物質並未掉落到排水口，而是在旋轉的吸積盤上方及下方，以兩道相反方向的窄噴流，高速射出。」
This setting is known from active galaxies called quasars with monstrous black holes with millions of solar masses at their centers that shoot jets tens of thousands of lightyears into the cosmos. As SS 433 looks like a scaled-down version of these quasars, it has been dubbed a micro quasar.
這是來自，在中心具有數百萬太陽質量、將噴流射入數萬光年外之宇宙中的巨大黑洞，被稱為類星體之活躍星系的已知背景。因為SS 433看起來像是這些類星體的縮小版，因此已經被稱為微類星體。
The high-speed particles and the ultra-strong magnetic fields in the jet produce X-rays and gamma rays. “The accretion disc does not lie exactly in the plane of the orbit of the two objects. It precesses, or sways, like a spinning top that has been set up slanted on a table,” says Torres. “As a consequence, the two jets spiral into the surrounding space, rather than just forming a straight line.”
在上述噴流中的高速粒子及超強磁場，產生X-射線及γ-射線。Torres宣稱：「上述吸積盤並非正好位於，這兩天體的軌道面。它如同一顆，一直傾斜樹立於桌上旋轉的陀螺，產生進動。因此，這兩噴流成螺旋狀，進入周遭的太空中，而不是僅形成一條直線。」
The precession of the black hole’s jets has a period of about 162 days. Meticulous analysis revealed a gamma-ray signal with the same period from a position located relatively far from the micro quasar’s jets, which has been labeled as Fermi J1913+0515 by the scientists. It is located at the position of an unremarkable gas enhancement. The consistent periods indicate the gas cloud’s emission is powered by the micro quasar.
此黑洞噴流的進動，具有大約162天的週期。縝密的分析揭露了一種，具有來自座落於相對遠離，已經被此些科學家們稱為費米J1913+0515之微類星體噴流的位置，及相同週期的γ-射線信號。
“Finding such an unambiguous connection via timing, about 100 light years away from the micro quasar, not even along the direction of the jets is as unexpected as amazing,” says Li. “But how the black hole can power the gas cloud’s heartbeat is unclear to us.” Direct periodic illumination by the jet seems unlikely.
Li宣稱：「經由計時找到了，大約離該微類星體1百光年外，甚至並非沿著噴流方向的這樣明確關聯性，是非常令人訝異的。不過，他們並不清楚，此黑洞如何驅動該氣體雲的悸動。」藉由噴流來直接闡明此週期，似乎不太可能。
An alternative that the team explored is based on the impact of fast protons (the nuclei of hydrogen atoms) produced at the ends of the jets or near the black hole, and injected into the cloud, where these subatomic particles hit the gas and produce gamma rays. Protons could also be part of an outflow of fast particles from the edge of the accretion disc.
該團隊探索的替代方法是根據，在射流末端，亦即黑洞附近產生之快速質子(氫原子的原子核)，且被注入此氣體雲(在此這些亞原子粒子撞擊此氣體並產生γ-射線)的影響。質子也可能是來自吸積盤邊緣，快速顆粒外流的一部分。
Whenever this outflow strikes the gas cloud, it lights up in gamma rays, which would explain its strange heartbeat. “Energetically, the outflow from the disc could be as powerful as that of the jets and is believed to precess in solidarity with the rest of the system,” explains Torres.
每當上述外流質子撞擊此氣體雲時，以能解釋其異常悸動的γ-射線發出亮光。Torres解釋：「能量上，來自吸積盤外流的能量，可能與噴射流一樣強大。因此，被認為與該系其餘部分一致地產生進動。」
Further observations as well as theoretical work are required to fully explain the strange gamma-ray heartbeat of this unique system beyond this initial discovery. “SS 433 continues to amaze observers at all frequencies and theoreticians alike,” emphasizes Li. “And it is certain to provide a testbed for our ideas on cosmic-ray production and propagation near micro quasars for years to come.”
除了理論上的研究之外，也需要諸多進一步的觀測，來充分解釋超出該初步發現之異常γ-射線的悸動。Li強調：「在各種頻率，SS 433持續令觀察者及理論學家們感到訝異。因此，對未來幾年而言，有關鄰近微類星體之宇宙射線的生產及傳播，無疑地這將為咱們的見解，提供一處驗證台。」
原文網址：https://scitechdaily.com/mysterious-gamma-ray-heartbeat-coming-from-cosmic-gas-cloud-leaves-scientists-baffled-as-unexpected-as-amazing/
翻譯：許東榮
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