星系NGC 4696內的黑洞
NGC 4696: Energy from a Black Hole<br />
<br />
<img src="http://i17.tinypic.com/30cuec2.jpg" border="0" onclick="zoom(this)" onload="attachimg(this, 'load')" alt="" /><br />
<br />
組合影像提供: X-ray in red - NASA/ CXC/S.Allen (Kavli Inst., Stanford) et al.; <br />
Radio in blue - NRAO/G.Taylor (VLA); Infrared in green - NASA/ESA/W.Harris (McMaster Univ.) <br />
<br />
<font color="navy">Explanation:</font><br />
<font color="dimgray">In many cosmic environments, when material falls toward a black hole energy is produced as some of the matter is blasted back out in jets. In fact, such black hole "engines" appear to be the most efficient in the Universe, at least on a galactic scale. This composite image illustrates one example of an elliptical galaxy with an efficient black hole engine, NGC 4696. The large galaxy is the brightest member of the Centaurus galaxy cluster, some 150 million light-years away. Exploring NGC 4696 in x-rays (red) astronomers can measure the rate at which infalling matter fuels the supermassive black hole and compare it to the energy output in the jets to produce giant radio emitting bubbles. The bubbles, shown here in blue, are about 10,000 light-years across. The results confirm that the process is much more efficient than producing energy through nuclear reactions - not to mention using fossil fuels. Astronomers also suggest that as the black hole pumps out energy and heats the surrounding gas, star formation is ultimately shut off, limiting the size of large galaxies like NGC 4696. <br />
</font><br />
<br />
<font color="navy">說明:</font><br />
<font color="dimgray">在許多宇宙環境中，當物質掉向黑洞時，就會產生能量，而以噴流的方式把部份之物質噴出來。事實上這種黑洞引擎，可能是宇宙中效率最高的；至少星系級黑洞應是如此。這幅組合影像呈現了其中一例，一個擁有高效率黑洞引擎的楕圓星系NGC 4696。這個大星系離我們約有一億五千萬光年遠，是半人馬座星系團最明亮的成員。在X射線波段(紅色)探索NGC 4696，天文學家能夠量測掉落物質為超大質量黑洞添加"燃料"的速率，並用來與產生巨大電波輻射泡泡的噴流之能量輸出作比較。上面影像中的藍色區塊，就是這個跨度有一萬光年的泡泡。研究的成果證實，物質掉向黑洞而產生能量的過程，確實比核反應過程要有效率，而化石燃料就更沒得比了。天文學家也得出另一項結論，隨著從黑洞輸出的能量持續加熱周遭的雲氣，恆星形成活動最後會被打斷，因此也限制了像NGC 4696這類大星系的大小。</font><br />
<br />
<font size="2">資料來源: Scientific American<br />
Department of Physics, NCKU</font><font color="white"><font size="1"><br />
</font></font>