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What features of our solar system provide clues to how it formed?
1- Patterns of motions among large bodies: -
All planetary orbits are nearly circular and nearly lie in the same plane.
All planets orbit the sun in the same direction; counterclockwise.
Most planets rotate in the same direction in which the orbit, with fairly small axis tilts.
Most of the planet’s large moons exhibit similar properties in their orbits around their planets such as the orbiting in their planet’s equatorial plane and in the same direction as the planet’s rotation.
2- The Existence of two types of planets
Terrestrial planets; are the first four planets; Mercury, Venus, Earth and Mars. These planets are relatively small, dense with rocky surfaces and an a lot of metals deep within.
Jovian Planets are next 4 planets; Jupiter, Saturn, Uranus and Neptune. The Jovian planets are much larger in size and lower in average density than the terrestrial planets. They also have rings and many moons. They lack rocky surfaces and are made mostly of hydrogen compounds.
3- Asteroids and Comets
Asteroids are rocky objects that orbit the sun like planets but are much smaller. (Inner solar system) Comets are icy objects that also orbit the sun like planets are usually within the inner solar system, they may become visible to the naked eye with long, beautiful tails. (outer solar system)
4- Exceptions to the rules
- There are a few notable exceptions to the general rules. Two such exceptions are the rotation of Uranus and Venus:
- Uranus rotates nearly on its side and Venus rotates “backwards” (clockwise as viewed high above Earth’s North Pole)
What theory best explains the feature of our solar system?
The nebular theory, which holds that the solar system formed from the gravitational collapse of a great cloud of gas and dust, successfully explains all the major features of our solar system.
Where did the solar system come from?
The nebular theory starts with the idea that our solar system was born from a cloud of gas called the solar nebula that collapsed. The gas that made up the solar nebula contained hydrogen and helium from the big bang and heavier elements produced by stars.
-The orderly motions of our solar system today are a direct result of the solar system’s birth in a spinning, flattened cloud of gas.
- The ingredients of the solar nebula fell into four major categories:
1- Hydrogen and helium gas
2- Hydrogen compounds such as water, methane, ammonia
WHY are there 2 major types of planets?
Planet formation began around tiny “seeds” of solid metal, rock, or ice that condensed from gas and then grew through accretion. In the inner solar system, temperatures were so high that only metal and rock could condense, which explains why the terrestrial planets are made of rock and metal. In the outer solar system, cold temperatures allowed much more ices to condense along with metal and rock. Icy object grew large enough for their gravity to draw in hydrogen and helium gases, forming the massive Jovian planets.
How do we explain the existence of our moon and other exceptions to the rules?
Most of the exceptions probably arose from collisions or close encounters with leftover objects. Our moon is most likely the result of a giant impact between a mars-size object and the young earth
- Our solar system began to form around 4.55 billion years ago
How do we detect planets around other stars?
So far, we are best able to detect extra-solar planets indirectly by observing the planets effect on the star it orbits. Most discoveries have been made using the Doppler technique, which help reveal the gravitational tug of a planet on a star. We can also search for transits and ellipses.
How do extrasolar planets compare in our solar system?
The known extrasolar planets are all much more massive than earth. Many of them orbit surprisingly close to their stars or have large orbital eccentricities.