About ESA
The European Space Agency (ESA) is Europe’s gateway to space. Its mission is to shape the development of Europe’s space capability and ensure that investment in space continues to deliver benefits to the citizens of Europe and the world.
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Space in Member States
Find out more about space activities in our 23 Member States, and understand how ESA works together with their national agencies, institutions and organisations.
Germany
Austria
Belgium
Denmark
Spain
Estonia
Finland
France
Greece
Hungary
Ireland
Italy
Luxembourg
Norway
The Netherlands
Poland
Portugal
Czechia
Romania
United Kingdom
Slovenia
Sweden
Switzerland
Science & Exploration
Exploring our Solar System and unlocking the secrets of the Universe
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Enabling & Support
Making space accessible and developing the technologies for the future
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Mass affects orbiting bodies
An orbit is the curved path that an object in space (such as a star, planet, moon, asteroid or spacecraft) takes around another object due to gravity.
Gravity causes objects in space that have mass to be attracted to other nearby objects. If this attraction brings them together with enough momentum, they can sometimes begin to orbit each other.
Objects of similar mass orbit each other with neither object at the centre, whilst small objects orbit around larger objects. In our Solar System, the Moon orbits Earth, and Earth orbits the Sun, but that does not mean the larger object remains completely still. Because of gravity, Earth is pulled slightly from its centre by the Moon (which is why tides form in our oceans) and our Sun is pulled slightly from its centre by Earth and other planets.
During the early creation of our Solar System, dust, gas, and ice travelled through space with speed and momentum, surrounding the Sun in a cloud. With the Sun being so much larger than these small bits of dust and gas, its gravity attracted these bits into orbit around it, shaping the cloud into a kind of ring around the Sun.
Eventually, these particles started to settle and clump together (or ‘coalesce’), growing ever larger like rolling snowballs until they formed what we now see as planets, moons, and asteroids. The fact that the planets were all formed together this way is why all the planets have orbits around the Sun in the same direction, in roughly the same plane.
