The eight planets of our Solar System
- large globe-shaped objects that orbit a star, such as our Sun.
- begin life at the same time as their star – from the leftover clouds of gas and dust.
Artist’s conception of a very young star encircled by a disk of gas and dust,
the raw materials from which rocky planets such as Earth are thought to form.
- planets are never more than 5% of the mass of our Sun – if they were bigger, they would be stars.
- terrestrial planets – surface of solid rock; others called gas planets – do not have a solid surface, just clouds.
- our Solar System has eight planets – Pluto was ninth, but it is very small and now it’s called a planetoid (dwarf planet).
Extrasolar planets or Exoplanet
The way that a young exoplanet interacts with its star’s disc
of dust and gas determines the type of exoplanet that will ultimately form.
- over 200 plants have been detached orbiting other stars – it’s called extrasolar planets or Exoplanets
- extrasolar planets are too far away to see, but can be detached by its making their stars appear to wobble.
- many known extrasolar planets are giants, bigger than Jupiter; they orbit rapidly, closer to their stars than Mercury is to the Sun.
- today improved detection techniques may reveal smaller planets orbiting further out in space.
Exoplanets – planets orbit the stars in the Milky Way.
Moons of our Solar System
- moons are the natural satellites of planets – most are small rock globes that continually orbit the planet – held in place by the planet’s gravity.
- as of October 2008, more than 176+ known natural moons in our Solar System.
- every planet in our Solar System has a moon or some moons, apart from Mercury and Venus.
- very few of the moons have atmospheres – including Saturn’s moon Titan, Jupiter’s Io and Neptune’s Triton.
One of the moons have atmosphere – Saturn’s moon Titan
- Jupiter’s moon – Ganymede, largest moon in the Solar System.
- second largest is Saturn’s moon – Titan; icy-cold, and is only moon with thick atmosphere of nitrogen gas. (wikipedia – Titan)
- smallest moons are icy lumps just a few kilometers across, rather like asteroids.
Saturn’s moon- Iapetus
Saturn’s moon – Iapetus
Colour map of Iapetus
- Iapetus; white on one side and black on the other side.
Saturn’s moon – Enceladus
Saturn’s moon – Enceladus
- Enceladus; only 312 miles across, and its icy surface reflects almost all the sunlight.
- a largely icy world.
- Cryovolcanic activity in Enceladus is sending geysers of water ice particles out from underneath the surface.
- The Cassini spacecraft has imaged these geysers spouting from so-called “tiger stripes” vent areas on this moon.
- Enceladus is now known to have a subsurface ocean made of liquid water – images from the Cassini spacecraft helped mission scientists deduce and prove the existence of that ocean.
List of natural satellites