메시어 M87 은하계는 커티스가 1918년에 관찰했다. 별자리는 처녀자리 (Virgo)다.
M87 은하계 블랙홀 지름은 400억 km이고 지구 크기의 300만배이다.
이 블랙홀은 지구로부터 5억 조 km 떨어져 있다.
전 세계에 퍼져 있는 8개의 천체 망원경이 이 블랙홀을 촬영했다.
사진에 나타난 M87 은하계의 블랙홀 크기는 태양계 전체 크기보다 더 크다. 태양의 질량보다 65억 배 이상 크다. 아직 그 빛이 어떻게 생성되었는지는 더 연구해야 한다. 블랙홀 사진에서 아주 밝은 '불의 고리'가 보인다.
밝은 후광은 과열된 가스가 블랙홀로 떨어질 때 생긴 것이다. 그 빛은 수십억개의 별들을 합친 것보다 더 밝다. 이런 이유 때문에, 우리가 지구에서 그 블랙홀을 관찰할 수 있었다.
중앙에 있는 검정 원의 가장자리는 가스가 블랙홀로 빨려들어가는 지점이다. 블랙홀은 엄청난 크기의 중력을 보유한 물체이고, 심지어는 빛도 탈출할 수 없다.
중심부 검정 부분은 실제로는 블랙홀이 아니다. 그곳에는 엄청난 많은 별들이 서로 뭉쳐져 있고 빠르게 움직이고 있다.
블랙홀 위에 '사건 지평면 Event Horizon'이라고 명명된 우주 영역이 있다. 이것이 바로 '돌아올 수 없는 지점 a point of no return'이다. 이 지점을 지나면 블랙홀의 중력 효과를 피할 수 없다.
하이노 팔케 (Heino Falcke:독일 1966) 교수가 대학원생 시절이었던 1993년에 이 블랙홀의 사진을 찍을 기획을 했다. 그는 블랙홀 주변이나 가까운 곳에서 전파가 방출될 것이라고 전제하고, 지구의 망원경이 그 전파 (radio emission)을 감지할 수 있을 것이라고 봤다.
하이노 팔케는 1973년에 발표된 한 논문에서, 엄청난 크기의 중력 때문에, 블랙홀은 실제보다 2.5배 더 크게 보인다는 것을 회상했다.
그 이후 20년 동안 하이노 팔케는 자기 주장을 펼치면서, 유럽 연구 위원회 (European Research Council)를 설득해서 연구비를 책정받았다. 국가 과학재단 (NSF)과 동아시아 연구기관들이 나중에 합류해서 4천만 파운드를 투자했다.
한 개 망원경으로는 부족해서, 8개의 망원경을 사용했다. 8개 망원경의 협력 체제를 구축한 과학자는 셰퍼드 돌러먼 (Sheperd Doeleman) 이었다. 그 8개의 망원경들이 '사건 지평면 망원경 the Event Horizon Telescope' 네트워크를 만들었다.
Sheperd Doeleman 은 이러한 전 지구적 망원경 협력체제와 실천은 '비범한 과학적 개가'라고 했다.
한 세대 전까지만 해도 거의 불가능한 작업이라고 봤기 때문이다. 이번에 우리 은하계 "the Milky Way"에 중심에 있는 블랙홀 이미지도 만들어냈다. 그러나 5500만 광년이나 떨어져 있는 M87 블랙홀보다 더 어려운 작업이었다.
그 이유는 우리 은하계에 있는 블랙홀이 훨씬 더 적고 흐렸기 때문이다. (이 블랙홀은 M 87 블랙홀에 비해 1000배 더 가깝지만, 1000배 더 적었다 )
[후기] 나도 늘 공기를 어떻게 양파처럼 자를까? 생각은 해오고 있고, 공기도 어떤 물질처럼 '층 layer'이 있다고 상상해오고 있다. 공상일지 모르지만, 그 공기 층을 마치 문처럼 열고 들어가면 미국에서 한국까지 눈 깜짝할 사이나 적어도 30분이면 도착하지 않을까? 그런 희망이 있다.
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First ever black hole image released
By Pallab Ghosh-
The first ever picture of a black hole: It's surrounded by a halo of bright gas
Astronomers have taken the first ever image of a black hole, which is located in a distant galaxy.
It measures 40 billion km across - three million times the size of the Earth - and has been described by scientists as "a monster".
The black hole is 500 million trillion km away and was photographed by a network of eight telescopes across the world.
Details have been published today in Astrophysical Journal Letters.
It was captured by the Event Horizon Telescope (EHT), a network of eight linked telescopes.
Prof Heino Falcke, of Radboud University in the Netherlands, who proposed the experiment, told BBC News that the black hole was found in a galaxy called M87.
"What we see is larger than the size of our entire Solar System," he said.
"It has a mass 6.5 billion times that of the Sun. And it is one of the heaviest black holes that we think exists. It is an absolute monster, the heavyweight champion of black holes in the Universe."
Media caption
Prof Heino Falcke: "We still have to understand how the light is generated"
The image shows an intensely bright "ring of fire", as Prof Falcke describes it, surrounding a perfectly circular dark hole. The bright halo is caused by superheated gas falling into the hole. The light is brighter than all the billions of other stars in the galaxy combined - which is why it can be seen at such distance from Earth.
The edge of the dark circle at the centre is the point at which the gas enters the black hole, which is an object that has such a large gravitational pull, not even light can escape.
Image copyright
DR JEAN LORRE/SCIENCE PHOTO LIBRARY
Image caption
Astronomers have suspected that the M87 galaxy has a supermassive black hole at its heart from false colour images such as this one. The dark centre is not a black hole but indicates that stars are densely packed and fast moving
The image matches what theoretical physicists and indeed, Hollywood directors, imagined black holes would look like, according to Dr Ziri Younsi, of University College London - who is part of the EHT collaboration.
"Although they are relatively simple objects, black holes raise some of the most complex questions about the nature of space and time, and ultimately of our existence," he said.
"It is remarkable that the image we observe is so similar to that which we obtain from our theoretical calculations. So far, it looks like Einstein is correct once again."
But having the first image will enable researchers to learn more about these mysterious objects. They will be keen to look out for ways in which the black hole departs from what's expected in physics. No-one really knows how the bright ring around the hole is created. Even more intriguing is the question of what happens when an object falls into a black hole.
What is a black hole?
A black hole is a region of space from which nothing, not even light, can escape
Despite the name, they are not empty but instead consist of a huge amount of matter packed densely into a small area, giving it an immense gravitational pull
There is a region of space beyond the black hole called the event horizon. This is a "point of no return", beyond which it is impossible to escape the gravitational effects of the black hole
Prof Falcke had the idea for the project when he was a PhD student in 1993. At the time, no-one thought it was possible. But he was the first to realise that a certain type of radio emission would be generated close to and all around the black hole, which would be powerful enough to be detected by telescopes on Earth.
He also recalled reading a scientific paper from 1973 that suggested that because of their enormous gravity, black holes appear 2.5 times larger than they actually are.
These two factors suddenly made the seemingly impossible, possible. After arguing his case for 20 years, Prof Falcke persuaded the European Research Council to fund the project. The National Science Foundation and agencies in East Asia then joined in to bankroll the project to the tune of more than £40m.
Image caption
The eventual EHT array will have 12 widely spaced participating radio facilities
It is an investment that has been vindicated with the publication of the image. Prof Falcke told me that he felt that "it's mission accomplished".
He said: "It has been a long journey, but this is what I wanted to see with my own eyes. I wanted to know is this real?"
No single telescope is powerful enough to image the black hole. So, in the biggest experiment of its kind, Prof Sheperd Doeleman of the Harvard-Smithsonian Centre for Astrophysics led a project to set up a network of eight linked telescopes. Together, they form the Event Horizon Telescope and can be thought of as a planet-sized array of dishes.
Image copyright
KATIE BOUMAN
Image caption
The data was stored on hundreds of hard drives which were flown to a central processing centre. There was too much of it to be sent over the internet
Image copyright
JASON GALLICCHIO
Each is located high up at a variety of exotic sites, including on volcanoes in Hawaii and Mexico, mountains in Arizona and the Spanish Sierra Nevada, in the Atacama Desert of Chile, and in Antarctica.
A team of 200 scientists pointed the networked telescopes towards M87 and scanned its heart over a period of 10 days.
The information they gathered was too much to be sent across the internet. Instead, the data was stored on hundreds of hard drives that were flown to a central processing centres in Boston, US, and Bonn, Germany, to assemble the information. Prof Doeleman described the achievement as "an extraordinary scientific feat".
"We have achieved something presumed to be impossible just a generation ago," he said.
"Breakthroughs in technology, connections between the world's best radio observatories, and innovative algorithms all came together to open an entirely new window on black holes."
The team is also imaging the supermassive black hole at the centre of our own galaxy, the Milky Way.
Odd though it may sound, that is harder than getting an image from a distant galaxy 55 million light-years away. This is because, for some unknown reason, the "ring of fire" around the black hole at the heart of the Milky Way is smaller and dimmer.