Milky Way's black hole is spinning incredibly fast, say scientists
The 'Milky Way' is seen in the night sky around telescopes and camps of people over rocks in the White Desert north of the Farafra Oasis southwest of Cairo May 16, 2015.
Our Milky Way Galaxy has billions of stars and planets. And at the centre, there is a supermassive black hole with unimaginable gravity that's holding the entire mass of stars and planets in place. And scientists have now found that the supermassive black hole is spinning incredibly fast.
Before we get there, a little conceptual understanding.
When we stand on the surface of the Earth, our weight isn't just determined by gravity but also by the centrifugal force generated by Earth's rotation. The centrifugal force tries to 'fling' us off the Earth but gravity, acting in opposite direction, glues us to the surface. The presence of this centrifugal force means that our weight at the equator is slightly less than that at the poles. The difference is 0.3 per cent. In the universe, everything that can rotate has a maximum rate of rotation.
The rule applies to black holes as well. But the key difference is, like planets, black holes do not have a physical surface. But they still have maximum rotation rate.
Due to its huge gravity, black hole distorts the spacetime fabric around it. The rotation of a black hole is defined in terms of this distortion.
In Einstein's equation of general relativity, the spin of a black hole is denoted by a property 'a' which can either have a value 0 or 1. Zero denotes least spin while 1 denotes maximum spin.
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According to a report in ScienceAlert, a team of scientists analysed radio and X-Ray observations of the black hole to estimate the spin.
The team found that the 'a'value of our black hole is between 0.84 and 0.96. The value is very close to 1, that is, the maximal speed. The scientists have hence underlined incredible rotational spin of the black hole at the centre of our galaxy.
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