![]() ![]() Galileo Galilei (1594 – 1642) was an Italian physicist, mathematician, astronomer and philosopher, considered an extremely Why are Io, Europa, Ganymede and Callisto known as the “Galilean moons” ? This would reduce the Earth’s ability to harbour life. Without the Moon acting as our anchor, our climate would be extremely unstable and Not only does it control the tides, it also stabilises Earth and reduces The battered Moon has a great effect on the Earth. While on Earth,įalling space objects are usually burnt up in the atmosphere, the Moon is covered in craters because it has no atmosphere. The Moon is being bombarded with a steady rain of meteoroids, asteroids and comets, as are most planets. Neil Armstrong became the first man on the Moon on July 21st, 1969, which is an impressive feat considering that the Moon is Moons are much further apart than shown here. (Io, Europa, Ganymede and Callisto - from top to bottom). On the right side of the picture are the Galilean moons Large as the Earth and wind speeds up to 450 km/h. This photocomposition shows Jupiter with its Red Spot, a gigantic complex storm about three times as However, using more and more sophisticated ways astronomers already found several dozen of such planets that are Earth-like and are located in the habitable zone of their stars. Which is why most of the planets we’ve found so far are big gas planets like Jupiter. The methods astronomers use are most effective when the planets are big, ‘wobble’ in the sky as the planet pulls at it. ![]() Have a much greater gravitational force, but if one measures a star’s position accurately enough, one might see it It’s not as obvious because the stars are so much bigger and therefore The gravitational effect of the star forces the planets into an orbit around it, but gravity works both ways and the gravitationalĮffect of the planet will be pulling on the star too. You can also find planets by their gravitational effects. The Earth’s line of sight, which in many cases would not happen. However, this method only works if the planet’s orbit takes it through To combat this, astronomers haveĭevised clever ways to see planets indirectly, using the parent star.įor instance, if you’re measuring the light from a star and find that its light dims at regular intervals then itĬould be because a planet is passing in front of it. Furthermore, extra-solar planetsĪre far away so they’re near impossible to see even if we knew where exactly to look. Planets don’t give off their own light, which is what makes them so hard to spot. The object must orbit its star, have enough gravitational pull to be spherical and have enough mass to clear the area around its orbit. There are 3 criteria needed to be defined as a planet. Pluto was considered a planet until 2006, when it was reclassified as a dwarf planet. It was the first planet to be discovered using a telescope, and Uranus, named after the Greek god of the sky. Saturn, named after the Roman god of agriculture. It’s the largest planet in the solar system. Mars, named after the Roman god of war because of its angry red colour. Also referred to by its Latin name, Terra. Venus, named after the Roman goddess of Love because it’s so bright in the skyĮarth, literally named after the dirt or soil it contains. Mercury, named after the Roman god of commerce, travel and thievery. They are (as we are moving away from the Sun) The other planets are named after Greek and Roman gods and goddesses. There are also many smaller bodies such as moons orbiting around planets, asteroids and comets.Įarth is the third planet from the Sun. The planetsĪre visible only because the light from the Sun reflects off their surface. The planets themselves count for less than 0.15% of the mass of the solar system. The solar system consists of the Sun at its centre and 8 planets moving in elliptical orbits around it. How exactly this happens is not yet fully understood, and is a large area of research for astronomers. Sunspots are created as the Sun’s intense magnetic field ‘churns’ up the Sun’s surface but The dark sunspots visible on the Sun surface are cooler regions, with temperatures of around 3800°c.Ī sunspot can be as large as 2-3 times the diameter of Earth (Source: Royal Swedish Academy of Science). We’ll go into the nuclear processes in more detail later on. This generates a vast amount of power: 386 billion billion megawatts (3.86x10 26 W). Of hydrogen nuclei are consumed in the central region of the Sun and fused together in this vast stellar nuclear reactor to These temperatures are generated by nuclear processes. Our Sun has a radius of 697,000 km (compare this to Earth’s radius of 6378 km) and comprises about 99.8% of the entireĪt the Sun’s core, temperatures are as high as 15,600,000°c (over 15 million degrees) but even the cooler surface is as ![]()
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