Nebular Hypothesis & Planetesimal Formation – Review Flashcards

A is a giant cloud of gas and dust where stars are born.

Nebula

The force that pulls particles together in space is called .

Gravity

After planetesimals stick and grow, they eventually become .

Planets

At the center of the spinning nebula, a hot dense mass called the forms.

Protosun

Conservation of angular momentum causes the collapsing nebula to flatten into a rotating .

Disk

The hypothesis states that the Solar System formed from a rotating cloud of gas and dust.

Nebular

The Nebular Hypothesis was first proposed by the philosopher in 1755.

Immanuel Kant

In 1796, without knowing Kant's work, developed a mathematical version of the nebular hypothesis.

Pierre-Simon Laplace

Together, Kant's and Laplace's ideas are known as the hypothesis.

Kant-Laplace

Modern refinements to the nebular hypothesis include the role of magnetic fields, turbulence, and transfer via solar winds.

Angular momentum

Stage 1 of the nebular hypothesis involves the existence of a slowly rotating .

Nebula

During gravitational collapse, the rotation of the cloud (slows down / speeds up).

Speeds up

Most of the mass moves toward the center, increasing temperature and pressure, forming the .

Protosun

The surrounding flattened disk where planets form is called the disk.

Protoplanetary

Tiny particles in the disk stick together to form kilometer-sized bodies known as .

Planetesimals

The process by which planetesimals merge into larger bodies is called .

Accretion

Evidence such as the HL Tauri image shows disks around young stars.

Protoplanetary

Planetary orbits lying nearly in the same plane support formation from a spinning disk.

Flattened

Planetesimals are small solid objects made chiefly of and ice.

Rock

The initial growth of dust grains into pebble-sized clumps is often called the phase.

Coagulation

Collisions of protoplanets over millions of years produced the Solar System's major .

Planets

Rocky planetesimals in the inner solar nebula formed the planets.

Terrestrial

The Earth formed about billion years ago through accretion of planetesimals.

4.6

Intense heating inside early Earth led denser materials like iron to sink and form the .

Core

Lighter silicate materials rose to form Earth's mantle and .

Crust

Volcanic released gases that built Earth's early atmosphere.

Outgassing

The early atmosphere lacked oxygen and was rich in water vapor, carbon dioxide, and .

Nitrogen

Condensation of water vapor produced prolonged rainfall that filled basins and created Earth's first .

Oceans

Radiometric dating of meteorites consistently gives ages of about billion years.

4.56

Similarity between Moon rocks and Earth's mantle supports the Impact Hypothesis.

Giant

Telescopes like Hubble and JWST observe planet-forming regions, validating the hypothesis.

Nebular

The Planetesimal Theory was formalized in the 1960s by Russian astronomer .

Viktor Safronov

NASA missions such as OSIRIS-REx return asteroid samples to provide evidence for solar system formation models.

Sample

According to the nebular hypothesis, conservation of explains why the cloud spins faster as