CEJ # 5

First glimpse of a black hole's spin

The study combined X-ray images from two telescopes, one old and one new

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Astronomers have measured the rate of spin of a super massive black hole for the first time - and it is big.

Measurements undertaken with two space-based X-ray telescopes imaged the black hole at the centre of galaxy NGC 1365.

The spin measurement, published in Nature, gives precious clues as to how the black hole grew and achieved supermassive status.

That growth influences the evolution of galaxies, so this simple number stands to teach scientists a great deal.

Black holes are notoriously difficult to study, since so much in astronomy depends on the detection of light - and beyond a certain distance, even that cannot escape.

Black holes are known to draw in material - gas and even stars - and stretching the very fabric of space-time at their edges. As matter goes in and gathers into what is called an accretion disk, it heats up and emits X-rays.

Previous attempts to quantify black holes' spins have attempted to analyse these X-rays - accounting for the violent processes within that can stretch and distort the X-rays' energies.

Those studies have until now focused on a fairly low-energy X-ray range. But those lower-energy X-rays can be further distorted by layers of gas between the black hole and the Earth, and previous spin observations have been contentious.

In a spin

Now Guido Risaliti of the Harvard-Smithsonian Center for Astrophysics and colleagues have looked at markedly higher energies - less subject to absorption in those gas layers - using Europe's XMM-Newton telescope and the recently launched Nustar telescope.

I think this is really cool that scientists can now study the spin of a black hole, because this could give us vital information to protect against the treat of black holes, and/or avoid them. Personally I am just interested with space, that's why I chose to pick this article.