Our sun resides in a little corner of the universe known as the Milky Way Galaxy, so named because of the Milky path that leads across our night sky. The Milky path that we see is made up of about 100 billion stars, each in a lazy orbit around the center of the galaxy that takes around 200 million years.
An observer on earth, looking towards the center of the galaxy would see the constellations of the Scorpius, the scorpion, and Sagittarius the archer. I think Sagittarius looks more like a teapot. Sagittarius is where our central supermassive black hole gets its name. Sagittarius a star, which is sometimes shortened to SGR A* as nickname.
This constellation is easiest to observe in July and August, when it's visible in the evening sky. Looking at the constellation of Sagittarius, we see that the bulge of the Milky Way is located at the westernmost end of the teapot. Since Earth hangs out in one of the outermost arms of the Milky Way galaxy, tilted with respect to the plane of the galaxy, it's actually easier for observers in the southern hemisphere to enjoy the view of the galactic bulge. Notice that the more we zoom into the center of the galaxy, the more crowded the stellar environment becomes.
Even though we call Sagittarius A* a supermassive black hole, it's a lightweight contender in the supermassive category. One of the reasons SGR A* isn't bigger is that it isn't presently eating very much at all. It sits in a region with many stars but none of them have strayed within gravitational reach for SGR A* to grab.
[궁수자리 A*]는 초거대 블랙홀이긴 하지만 그 급내에서는 작은 편이다. SGR A*가 크지 못한 이유는 주변에 흡입할 별이 많지 않아서 크게 성장하지 못했다.
So, what's so special about Sagittarius A*? Well, it's probably the only supermassive black hole within about 2.5 million light years. The next nearest known supermassive black hole is at the core of the Andromeda galaxy.
SGR A*이 특별하다는데 왜 때문이죠? 2백 5십만 광년 이내에서 발견할 수 있는 초거대 블랙홀로서는 유일하다는 점이다[우리은하 중심에 있다. 지구에서 약 2만 5천 9백 광년 떨어져 있다]. 그 다음으로 가까운 초거대 블랙홀은 안드로메다 은하 중심에 있다[2백 55만 광년].
Due to the proximity to Earth, SGR A* is the most studied supermassive black hole, and we are fortunate that it isn't currently eating. This gives us an excellent opportunity to see the environment around it without being blinded by the glare from the accretion disc.
지구에서 가까운 만큼 많이 관측되고 연구된 초거대 블랙홀이다. 그리고 아주 다행스럽게도 현재 흡입중이 아니다. 이는 강착원반으로부터 나오는 방출광이 없으므로 관측을 방해하는 요소가 없다는 뜻이다.
If SGR A* isn't currently feeding, how do we even know it's there? While scientists using ESO's very large telescope, have actually image the core of the galaxy and revealed the motion of the stars and dust clouds surrounding the central black hole.
From 2000 to 2011, this video shows the stars orbiting Sagittarius A*. Which reveal to astronomers just how massive the black hole is.
2000년에서 2011년사이에 궁수자리 A*을 관측한 사진을 이어붙인 영상이다. 블랙홀의 질량을 짐작케 하는 사진이다.
In fact, one of the objects called G2, isn't a star at all, but a cloud of molecular dust. Researchers predicted that G2 would be captured by the gravity of the supermassive black hole, with a collision around 2014. They predicted it would be consumed by Sagittarius A*, causing it to light up in the X-ray spectrum. However, when G2 passed the central object not much happened. It's still a mystery why G2 wasn't eaten by Sagittarius A*.
[블랙홀 인근에] G2라고 불리는 천체가 있는데 별이라기 보다 분자먼지 구름이다. 연구자들은 G2가 초거대 블랙홀에 의해 붙들려 들었다가 2014년경 충돌하리라고 예상했다. 궁수자리 A*에 빨려들어 가면서 X선 방출이 있을 거라고 기대 했다. 하지만 G2는 [블랙홀이 있을 것이라고 짐작되는] 중심부를 비켜가면서 큰 사건은 없었다. 지금도 왜 G2가 초거대 블랙홀에 의해 먹히지 않았는지 미스테리로 남아있다.
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[인터뷰] [커세라 페이지]
Why is Sagittarius A* important?
Interview with Dr. Fiona Harrison, Professor at Caltech University
Sagittarius A star is the very heart of the Milky Way. And at the very heart of the Milky Way, there's a supermassive black hole that's 4 million times the mass of the sun. But what's mysterious about this black hole is unlike many others that are quite active, there's a lot of dust and gas around it, but it's very quiet. It doesn't emit much radiation. You can see it in the radio. And about once a day, you can see it flare in the X-ray. And what these flares can teach us is what's going on in the region very close to this supermassive black hole. And eventually, we're going to have a huge array of radio telescopes that may even be able to image the event horizon of this supermassive black hole. It will be our first real view of the event horizon. We could tell, for example, if this black hole is spinning or not, which would tell us something about how it formed. And so by studying Sagittarius A star across the entire spectrum, because it's so close, we can learn what's going on with these dormant black holes. What is the center? It's the closest supermassive black hole that we have to study.
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