galactic centre

Definition

Astronomy

  • The centres of galaxies are often highly disturbed and energetic. The core of our own galaxy, which lies in Sagittarius, cannot be observed in visible light because of the dense dust and gas clouds obscuring it. But it is highly active in X and gamma ray frequencies, which has given rise to theories that it contains a massive black hole. The galactic core is seen in radio wavelengths – radio astronomers call it Sagittarius A – and at these frequencies it resembles a quieter version of the active nuclei of Seyfert galaxies and quasars. The galactic centre seems to give off about 0.1 per cent of the radiation of the whole galaxy – about 80 million times as much as the Sun – in a tiny fraction of the overall volume of the galaxy.
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