The importance of the Sun in our Solar System
1) 98,9% of all mass => gravitational pool gathers all orbiting object around the centre (the Sun itself)
2) the only source of light and heat (other objects just reflect star’s light)
3) solar wind (charged particles) interacts with planetary magnetic fields and influences planetary atmospheres
Solar wind
A continuous stream of charges particles moving in all directions from the Sun (in plasma state)
4 features of our Solar System
1) all planetary objects move in an organised pattern;
2) 2 types of planets: terrestrial planets (Mercury, Venus, Earth, Mars) and Jovian planets (Jupiter, Saturn, Uranus, Neptune);
3) asteroids (Asteroid belt), comets (Kuiper belt);
4) there’re exceptions to the first 3 rules (the Earth’s Moon, Venus’s rotation, Uranus’s axis tilt)
Comparison of terrestrial and Jovian planets
4 features of our solar system
1) motion of planetary objects in organised way (orbit in one direction, the same as rotate)
2) 2 types of planets: terrestrial (Mercury, Venus, Earth, Mars) and Jovian (Jupiter, Saturn, Uranium,Neptune)
3) asteroids (Asteroid belt) and comets (Kuiper belt)
4) exceptions: Venus’s backward rotation, Earth’s Moon large size, Uranium almost horizontal tilt axis
Comparison of terrestrial and Jovian planets
Terrestrial Jovian
Distance closer to the Sun and to each other Farther from the Sun
Size Relatively small Large
Density Higher density Lower density
Surface Solid surface Lack solid service
Moons A few (if any) and no rings Many moons and rings
Nebular Theory
Proposed by Kant and Laplase (independently)
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States that our Solar System formed from the gravitational collapse of a cloud of gas (this particular gas is called Solar Nebula)
What caused the orderly patterns of motion?
1) heating — conservation of energy — t ⬆️ as it collapses — Ep -> Ek -> E(thermal)
2) spinning — conservation of angular momentum — r⬇️ -> v⬆️
3) flattering — disk shape — a consequence of collision between particles
Why are there 2 types of planets?
The main reason is the distance from the heat centre — terrestrial planets were formed within warm inner part of the disk, whereas Jovian planets formed in the colder outer regions ——>
——> formed by the process of condensation (- the process of formation of solid and liquid particles from a cloud of gas) ——> different material condense at different temperatures ——>
——> rocky and metal materials - hotter t⬆️;
Hydrogen and helium - cooler t⬇️
Different material and their condensation temp
Hydrogen and helium Hydrogen compounds Rock Metal
98% 1.4% 0.4% 0.2%
Never condense Condense into ices at low t < 150K Condense into solid form at t 500-1300K Condense into solid form a at t 1000-1600K
Frost line
- the boundary in the solar nebula beyond which ices could condense, only rock and mental could condense within the frost line (located between Mars and Jupiter)
Condensation
- the formation of solid and liquid particles from cloud of gas
Accretion
The process by which small objects gather together to make larger objects
(—> planetesimals)
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Have evidence of accretion from meteorites (-rocks that have fallen on Earth from outer space)
Planetasimals
The building bricks of planets fronted by accretion
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In case of Jovian planets: they began as icy planetesimals; then capture hydrogen and helium growing in size (capturing even more by increased gravitational force)
What happens to the vast majority of h and h?
Clearing the nebula
It was cleared away by high-energy radiation ☢️ and solar wind 💨
The origins of asteroids and comets
Asteroids and comets are leftover planetesimals from the era of planet formation
Impact craters
- bowl-shaped depression of an object that strikes a planetary surface
Most happened during the heavy bombardment period
Heavy bombardment
The period in the 1st few hundreds mill years after the solar system formed during which planetary accretion caused most impact craters happen on the surface of -planetary objects
How do we explain exceptions (4th feature of our Solar System)?
1) Captured moons - unusual motion direction —> gravitational encounter due to random nature of capture process
2) Our Moon - hypothesis that the Moon was formed after giant impact — so debris of Earth after the collision participated in accretion —> were captured by the Earth’s gravity on its orbit —> the Moon
3) tipping Uranus and Venus — also after the giant impact (supposition again)
Giant impact
Collision between a forming planet and a very large planetesimal
How we determine the age of the Solar System
1 — by examining the age of the oldest rocks in the Solar System
2 — through radiometric dating (-the process of determining the age of a rock by comparing present amount of a radioactive substance with the amount of its decay product.
Proportion of various atoms and isotopes in the rock
Radiometric dating
The Solar System is about ≈ 4.5 billion years
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- the process of determining the age of a rock by comparing present amount of its radioactive substance to the amount of its decay product
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Radioactive - means a spontaneous change in an atomic nucleus == decay - happens always at the same rate - which is stated in terms of half-life — the time it takes for the half of the nuclei in a given quantity of a radioactive substance to decay
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T(age)= t(half-life)*(ln(current amount/ original amount)/ln(1/2)
Half-life
The time it takes for the half of the nuclei in a given quantity of a radioactive substance to decay
1/2 -> 1/4 -> 1/8 -> 1/16
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T (the age) = t(half-life)*(ln(current amount/original amount)/ln(1/2)
Brief summary of stages of s.s-m formation (in 3 stages)
Collapse —> Condensation —> Accretion
