Enrichment: Astronomy Related
Our solar system was formed about 4.5 billion years ago from a dense cloud of interstellar gas and dust. The cloud collapsed, possibly due to the shockwave of a nearby exploding star, called a supernova.
At the center, the sun was formed due to matter collapsing together due to gravity. Matter farther out clumped together due to gravity to form planets and moons. It formed eight planets and more than 150 moons in our solar system.
Our solar system consists of our star, the Sun, and eight planets (Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, and Neptune), all bound to the Sun by gravity. There are dwarf planets such as Pluto, about 150 moons, millions of asteroids, and comets bound to the Sun by gravity. Beyond our solar system, there are thousands of planetary systems orbiting other stars in the Milky Way galaxy. Our solar system is located in the Milky Way galaxy.
| PLANET NAME | AU* | DISTANCE FROM SUN (million) | # of MOONS | DIA METER | ORBIT PERIOD (a year) | ROTATION PERIOD (a day) |
| MERCURY | 0.4 | 37 miles (60 km) | 0 | 3,060 miles (4,879 km) | 88 earth-days | 59 earth-days |
| VENUS | 0.7 | 65 mile (105 km) | 0 | 7,565 miles (12,104 km) | 224.7 earth-days | 243 earth- days |
| EARTH | 1.0 | 93 mile (150 km) | 1 | 7,917 miles (12,742 km) | 365 days | 24 hours |
| MARS | 1.5 | 140 miles (225 km) | 2** | 4220 miles (6752 km) | 687 earth-days | 24 hrs 39 min |
| JUPITER | 5.2 | 484 miles (778 km) | 79 | 88,695 miles (142,800 km) | 11.84 earth-years | 10 earth-hours |
| SATURN | 9.5 | 884 miles (1,422 km) | Ring | 74,897 miles (120,536 km) | 29.5 earth-years | 10 hours 45 min |
| URANUS | 19.2 | 1,786 miles (2,874 km) | 27 | 31,757 miles (51,108 km) | 84 earth-years | 17.9 earth-hours |
| NEPTUNE | 30 | 2790 miles (4490 km) | 14 | 30,775 miles (49,528 km) | 164.8 earth-years | 19.1 earth-hours |
Of the eight planets, Mercury and Venus are the only ones with no moons
*AU = One astronomical unit.
Astronomical Unit is defined as the distance between Sun and the earth, which is 93 million miles (150 million kilometers).
**Deimos and Phobos
Our Earth and Moon
| The Earth We Live on Facts | |
| Age | 4.5 billion Years |
| Distance from Sun | 93 million miles (150 million km) |
| Orbits around | Sun |
| Orbit period | 365 days |
| Radius | 4,000 miles (6,400 km) |
| Acceleration due to gravity | 9.8 meter/ sec^2 |
Our Moon:
Our Moon orbits around planet Earth and is Earth’s only natural satellite. It is the fifth-largest satellite in the Solar System. It takes the moon 27 earth-days to complete one orbit around the earth.
| Our Moon Facts | |
| Age | 4.5 billion Years |
| Distance from Earth | 238,000 miles (385,000 km) |
| Orbits around | Earth |
| Orbit period | 27 earth-days |
| Radius | 1,079.4 miles |
| Acceleration due to gravity | 1.62 meter/ sec^2 |
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