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Making the solar system

Introduction

Our solar system is thought to have formed around 4.5 billion years ago and most astronomers now agree that the nebular theory best describes its origin. In this model the Sun, planets, asteroids and comets originated within a rotating cloud of gas and dust - the solar nebula.

An artist's impression of the forming Sun and its proto-planetary disk
This material would have been within a star-forming region typical of those seen today such as the dark region behind the Orion nebula.

An artist's impression of the forming Sun and its protoplanetary disk.
Image courtesy Pat Rawlings/NASA/JPL

The solar nebula condensed into a rotating disk of gas and dust (a proto-planetary disk or proplyd) with the Sun at its centre. Planets and other bodies formed through the accretion of planetesimals - component pieces of rock and dust - and nebular gas.

Views of forming planetary systems in the Orion nebula taken by the Hubble Space Telescope
Views of forming planetary systems in the Orion nebula taken by the HST.Image: Mark McCaughrean (Max-Planck-Institute for Astronomy), C. Robert O'Dell (Rice University), and NASA
Direct evidence for the nebular theory came in 1994 when the Hubble Space Telescope (HST) sent back pictures of proplyds in the visible part of the Orion nebula. Each proplyd is comparable in size to our own solar system and is centred on a young star.

Over the next 100,000 years some of them should collapse into a variety of planetary systems.



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