Outer solar system
|
|
| Age | 4.568 billion years |
|---|---|
| Location | |
| System mass | 1.0014 Solar masses |
| Nearest star |
|
| Nearest known planetary system | Proxima Centauri system (4.25 ly) |
| Semi-major axis of outer known planet (Neptune) | 30.10 AU (4.503 billion km) |
| Distance to Kuiper cliff | 50 AU |
|
Populations
|
|
| Stars | 1 (Sun) |
| Known planets | |
| Known dwarf planets | |
| Known natural satellites |
470
|
| Known minor planets | 707,664 (as of 2016-03-07) |
| Known comets | 3,406 (as of 2016-03-07) |
| Identified rounded satellites | 19 |
| Invariable-to-galactic plane inclination | 60.19° (ecliptic) |
| Distance to Galactic Center | 27,000 ± 1,000 ly |
| Orbital speed | 220 km/s |
| Orbital period | 225–250 Myr |
| Spectral type | G2V |
| Frost line | ≈5 AU |
| Distance to heliopause | ≈120 AU |
| Hill sphere radius | ≈1–3 ly |
The Solar System is the gravitationally bound system comprising the Sun and the objects that orbit it, either directly or indirectly. Of those objects that orbit the Sun directly, the largest eight are the planets, with the remainder being significantly smaller objects, such as dwarf planets and small Solar System bodies. Of the objects that orbit the Sun indirectly, the moons, two are larger than the smallest planet, Mercury.
The Solar System formed 4.6 billion years ago from the gravitational collapse of a giant interstellar molecular cloud. The vast majority of the system's mass is in the Sun, with most of the remaining mass contained in Jupiter. The four smaller inner planets, Mercury, Venus, Earth and Mars, are terrestrial planets, being primarily composed of rock and metal. The four outer planets are giant planets, being substantially more massive than the terrestrials. The two largest, Jupiter and Saturn, are gas giants, being composed mainly of hydrogen and helium; the two outermost planets, Uranus and Neptune, are ice giants, being composed mostly of substances with relatively high melting points compared with hydrogen and helium, called volatiles, such as water, ammonia and methane. All planets have almost circular orbits that lie within a nearly flat disc called the ecliptic.
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Wikipedia