It is about 1,300 light years away. The bubble has been created by the intense radiation from the cluster of young stars at its centre. The four brightest stars are popularly known as 'The Trapezium'. Their radiation causes the inside surface of the cavity to glow. Easily visible to the naked eye in the constellation Taurus, the Pleiades is a cluster of about 3000 stars in all.
Most people can pick out the six brightest without the help of binoculars or a telescope.
It is about 400 light years away and 30 light years across.