2.1 Solar nebular model Flashcards
When was the Big Bang?
14 billion years ago (14 Ga)
When was the solar system formed?
4.6 billion years ago (4.6 Ga)
What is a nebula?
A giant cloud of molecular hydrogen and dust.
What happened to the nebula to begin the creation of the solar system?
It collapsed, possibly due to the shockwave from a nearby exploding star) and became denser.
What is a protoplanetary disc?
A rotating flat gaseous cloud that was created due to the collapse of the solar nebula.
What occurred as a result of the heat and high density occurring at the centre of the protoplanetary disc?
It triggered nuclear fusion, increasing the temperature of the surface of the star at the centre of the protoplanetary disc.
What is meant by the term accretion?
An increase in mass by the addition of material e.g. by rocky particles colliding.
What is a planetesimal?
A small body of rocky material that has been created by gravitational and electrostatic forces. They are around 1 km in diameter.
What is a protoplanet?
It forms when planetesimals accrete (join together). They are approximately the size of the moon.
Approximately how long did it take for protoplanets to collide and form the terrestrial planets?
Up to 1 billion years.
Why did giant gas planets form in the outer reaches of the solar system?
They formed from the less dense elements that was sent further away from the sun when it collapsed and produced a shockwave.
What are asteroids?
The left over planetesimals that did not form planets.
What are meteorites?
Fragments of asteroids.
How did the moon form?
A protoplanet impacted the young Earth between 30 and 50 million years after the formation of the Solar System.
What assumption do we have to make in order to use meteorites as evidence for the Earth’s composition and structure?
All the material in the Solar System originated from the same source.
What feature do meteorites have that means that can be used as a record of planet formation?
The have remained unaltered since they were formed.
What is the evidence for the solar nebular hypothesis?
- The rocky planets are closest to the Sun and the gas giants further away
- Most solar system objects orbit and rotate in an organised fashion
Which type of meteorites represent the Earth’s core?
iron meteorites
What are iron meteorites composed of?
an alloy of iron and nickel
Which type of meteorites represent the Earth’s mantle?
stony meteorites
What are stony meteorites composed of?
silicate mineral including olivine, pyroxene and plagioclase feldspar
Which type of meteorite are thought to represent the overall composition of the Earth?
chondrites
What are chondrites composed of?
silicate minerals plus water, organic compounds, and chondrules
What are chrondules?
originally molten droplets, for example of olivine, which formed at high temperatures in the early solar cloud (found in chondrite meteorites)
Which type of meteorite is chemically similar to the Sun, except for the absence of hydrogen and helium?
chondrites
State three pieces of evidence for asteroid impact.
- the impact sites are circular and have a rim of broken rock built up of ejected material
- quartz grains may be violently shocked and even melted
- rock strata are tilted
- material at depth is brecciated (broken up)
- the ejected material falls back to the surface in an inverted sequence because material closer to the surface is ejected first and falls back to the surface earlier
What is the relationship between the size of an asteroid or meteorite impact and their frequency?
The larger the size of the impact, the less frequent the impacts are (negative correlation).
