Читать книгу Universe: The story of the Universe, from earliest times to our continuing discoveries - Peter Grego - Страница 17

The Sun, attended by its nine major planets and their satellites, along with hundreds of thousands of asteroids and comets, orbits the centre of a vast spiral galaxy of some 300 billion stars called the Milky Way. A middle-aged resident of the galactic suburbs, the Sun is located around 26,000 light years from the galactic centre – about half way from its centre to the edge, within one of the galaxy’s spiral arms. Orbiting the Milky Way at a speed of around 220km per second, the Sun has made around 20 galactic circuits since its birth around five billion years ago.

Measuring around four light years across (if we include the Oort Cloud), the Solar System occupies a tiny part of the Milky Way galaxy, some 100,000 light years in diameter. Indeed, the Sun would not be visible to the unaided eye from a distance of much more than 50 light years. Viewed from the Alpha Centauri system some 4.5 light years away, the Sun would appear as a bright star in the constellation of Cassiopeia.

Our location within the suburbs of the Milky Way spiral galaxy.