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Science@ESA (Episode 7): Planetary science - Exploring our backyard, the Solar System (Part 2)
In this seventh episode of the Science@ESA vodcast series Rebecca Barnes continues to journey through the wonders of modern astronomy bringing us closer to home as we begin to explore the Solar System. We'll discover the scale and structure of the Solar System, find out why we explore it and introduce the missions launched on a quest to further investigate our local celestial neighbourhood.
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Planetary science is the scientific study of planets (including Earth), moons, and planetary systems, in particular those of the Solar System and the processes that form them. It studies objects ranging in size from micrometeoroids to gas giants, aiming to determine their composition, dynamics, formation, interrelations and history.
It is a strongly interdisciplinary field, originally growing from astronomy and earth science, but which now incorporates many disciplines, including planetary astronomy, planetary geology (together with geochemistry and geophysics), physical geography (geomorphology and cartography as applied to planets), atmospheric science, theoretical planetary science, and the study of extrasolar planets. Allied disciplines include space physics, when concerned with the effects of the Sun on the bodies of the Solar System, and astrobiology.
There are interrelated observational and theoretical branches of planetary science. Observational research can involve a combination of space exploration, predominantly with robotic spacecraft missions using remote sensing, and comparative, experimental work in Earth-based laboratories. The theoretical component involves considerable computer simulation and mathematical modelling.
Planetary scientists are generally located in the astronomy and physics or earth sciences departments of universities or research centres, though there are several purely planetary science institutes worldwide. There are several major conferences each year, and a wide range of peer-reviewed journals.
The Solar System is made up of the Sun and all of the smaller objects that move around it. Apart from the Sun, the largest members of the Solar System are the eight major planets. Nearest the Sun are four fairly small, rocky planets - Mercury, Venus, Earth and Mars.
Beyond Mars is the asteroid belt - a region populated by millions of rocky objects. These are left-overs from the formation of the planets, 4.5 billion years ago.
On the far side of the asteroid belt are the four gas giants - Jupiter, Saturn, Uranus and Neptune. These planets are much bigger than Earth, but very lightweight for their size. They are mostly made of hydrogen and helium.
Until recently, the furthest known planet was an icy world called Pluto. However, Pluto is dwarfed by Earth's Moon and many astronomers think it is too small to be called a true planet.
An object named Eris, which is at least as big as Pluto, was discovered very far from the Sun in 2005. More than 1,000 icy worlds such as Eris have been discovered beyond Pluto in recent years. These are called Kuiper Belt Objects. In 2006, the International Astronomical Union decided that Pluto and Eris must be classed as "dwarf planets".
Even further out are the comets of the Oort Cloud. These are so far away that they are invisible in even the largest telescopes. Every so often one of these comets is disturbed and heads towards the Sun. It then becomes visible in the night sky.