8 Amazing Facts about our Solar System
Uranus - an outsider among the planets
1. Venus and Uranus turn backward
The planets normal rotation is CCW (counterclockwise), as seen from above the NCP (North Celestial Pole). That is, the sun normally rises in the east and sets in the west, just like on planet Earth. Yet there are two exceptions, Venus and Uranus, respectively the second and seventh planet from the sun, rotate CW (clockwise), that is backward. Uranus furthermore has an orbital tilt of 82 degrees rotating almost on its side.
2. Saturn would float in water
The four planets closest to the sun, also called the terrestrial planets, are made mainly of rock and metal. The next four are gas giants (Jupiter, Saturn, Uranus, Neptune) and have no solid surface. Density of the terrestrial planets is, understandably, higher than that of the outer planets. Especially Saturn has low density (0.70) even for a gas giant. Saturn is so light it would float if thrown into water.
Saturn - Gas Giant 10 AU from the sun
Gazing at the stars
3. Planets appear as stars in the sky
Ancient people simply distinguished the sun, the moon and the stars. Among the stars Sirius in the constellation of Canis Major (therefore sometimes called the 'dog star') is the brightest having the lowest apparent magnitude (scale is inverted by definition, low magnitude values stand for a high level of brightness). Yet there are other celestial objects that 'outshine' Sirius: Venus, Jupiter and sometimes even Mars appear brighter than Sirius. Even Saturn further out appears brighter than most stars. The planets, of course, simply reflect the sunlight and get their apparent brightness due to their relative nearness to Earth compared to the stars.
4. A year on Mercury lasts less than two days
A day, on any planet, is considered to be a full rotation. A day on Mercury, the first planet from the sun, lasts almost sixty (Earth) days. Furthermore, being close to the sun its orbital period is of only 88 days. This means a year on Mercury lasts just one and a half days.
Solar System Exploration
5. The hottest planet is not the one closest to the sun
One would expect the hottest planet to be the one closest to the sun. Yet Venus, the second in order and the planet closest to Earth, is even hotter than Mercury. This is due to Venus' thick atmosphere that traps the sun's heat reflected from the planet's surface. Both planets are far too hot to sustain life. If man is ever to become a multi-planet species he is well advised to head outward in search of new frontiers.
6. The mass of the solar system is almost entirely made of the sun
It takes 1,000 times the Earth to fill Jupiter, the largest planet of our solar system. Yet the mass of all planets of our solar system combined, including asteroids, is only 0,14% the mass of our solar system. The remaining mass of 99.86% is made up by the sun!
How big is the Solar System?
7. Pluto is nowhere near the edge of our solar system
Before being demoted to dwarf planet, on older charts Pluto appeared as the ninth and most outer planet. Yet Pluto is nowhere near the border of the solar system. It is estimated the edge of the solar system is still some 1,000 times farther out than Pluto. An Astronomical Unit (UA) is defined as the distance of the Earth from the sun (1 AU). While Pluto on average is 39,5 AU from the sun, the Oort comet cloud may extend some 50,000 AU or half a light year away into outer space. The closest star, Alpha Centauri (or rather Proxima Centauri) is 4.2 light years away. By comparison the light takes only 5.5 hours from the sun to reach Pluto.
Mount Everest XXL size
8. Mount Olympus dwarfs Mount Everest
Mars is much smaller than Earth, only about half the diameter of our blue planet. Yet the red planet's topography is truly XXL size. Mount Olympus dwarfs Mount Everest being almost three times as high (22 km, 13.6 mi). Mars' canyon Valles Mariners has an astonishing length of 4.000 km (2,500 mi) outsizing the Grand Canyon by far.