태양 보다 900배가 큰 초거성이 생생히 카메라에 잡혔다.
오리온 자리에 있는 1등성 베텔기우스가 칠레에 있는 유럽남방천문대의 극대배열전파망원경(이하 VLT)에 선명하게 포착됐다고 영국 BBC 방송이 보도했다.
베텔기우스는 지구에서 640광년이나 떨어져 있지만, 태양의 940배에 달하는 반지름을 가져 천구에서 10번 째로 밝은 별이다.
사진에는 이 별이 가스 기둥과 먼지를 분출하는 모습을 담겼으며 대기 가스가 상하로 빠르게 움직이며 거대한 장관을 이루는 모습도 나타났다.
오래된 별인 베텔기우스는 수천년 안에 폭발해 초신성이 될 것이라고 대다수의 천문학자들이 추측한다.
유럽남방천문대 연구진에 따르면 지금까지 이 별이 촬영된 적은 있었으나, 이렇게 자세하고 선명하게 형체가 잡힌 적은 없었다.
연구진은 “폭발 직전의 초거성 모습을 자세히 관찰할 수 있어 우주 연구에 도움이 될 것”이라 저널 천문학 및 천체물리학(Astronomy and Astrophysics)을 통해 자평했다.
한편 이 별이 폭발하면 수개월동안 지구의 밤하늘에서 보름달처럼 빛나고, 그 뒤에는 서서히 어두워지다가 성운이 된다고 한다.
이 별이 폭발하더라도 지구는 자기장만 흔들릴 뿐 생명체에는 지장이 없다고 전문가들은 입을 모았다.
사진설명=베텔기우스의 상상도(왼쪽), 실제 모습(오른쪽)
서울신문
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The Question
I have just became aware of the enormity of Betelgeuse. Do we know of stars that are larger than this? If so, approximately how many are of this scale are larger? Does a star have to be of this size to be a candidate for a black hole?The Answer
Betelgeuse (also known as alpha ori) is a very large star, an M supergiant. This is because it has evolved far from the state in which stars spend most of their lives, known as the main sequence. For stars on the main sequence, which includes our Sun, there is simple proportionality between size and mass, and also a simple scaling for luminosity. For evolved stars the situation is less simple. Betelgeuse is more than 1000 times larger than the Sun, and 50000 times as luminous, but onl y about 20 times as massive. Most of the light from Betelgeuse comes out in the infrared, however, which is very different from the Sun. One consequence of the advanced evolutionary state of Betelgeuse is that it probably was much more massive when it was on the main sequence, and has already lost a significant fraction of its mass (probably more than half) in a stellar wind. There are many stars that are as massive as Betelgeuse is now, and probably many that are as massive as Betelgeuse was when it was on the main sequence. Of the 100,000,000,000 (100 billion=10^11) or so stars in our galaxy, it is estimated that approximately 1% have main sequence masses greater than 30 times that of the Sun, which is where Betelgeuse may have started out. A very crude estimate is that such stars spend 1% of their lives as supergiants, which would suggest 10,000,000 stars similar to Betelgeuse in our galaxy. In spite of this fact, there are very few stars which are visible to the naked eye which are as large as Betelgeuse. This is simply a consequence of the fact that we can distinguish bright stars in onl y a small fraction of the galaxy. Another one is Mira, in the constellation Cetus. Mira is probably larger than Betelgeuse, so large that it is thought that the outer layers of the star are barely held together by gravity. Mira is known to pulsate and eject its outer layers, probably in large part because of its weak gravity. Possibly the most massive known star is eta carina, which may have been 150 times as massive as the Sun when it first formed, and may be 50 - 60 times as massive as the Sun currently. In the 1830s eta carina underwent a tremendous outburst during which it became a brilliant naked eye object and ejected an amount of gas with mass approximately equal to the mass of the Sun. It is likely that the minimum main sequence mass for a star which will eventually make a black hole is 8 - 10 times the mass of our Sun. This is quite a bit less than Betelgeuse had when it was on the main sequence, and there are many such stars in our galaxy. I hope this helps! Tim Kallman for Ask an Astrophysicist Prev |  Main |  Next |
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