Astronomy Final Review

Flashcards about the Interstellar Medium, Nebulae, Star Birth, and Planet Formation

What is the Interstellar Medium (IM)

The name for all material between the stars, made of gas and dust.

What is the composition of the Interstellar Medium (IM)

75% Hydrogen, 24% Helium, 1% Dark Dust

What is the temperature and Density of the Interstellar Medium

Very cold (10-100* K) and extremely low density

What does the composition of the Interstellar Medium (IM) prove?

That the sun was made from the IM.

What is a Nebula?

Any blob of gas and dust in space.

Where atoms stay together to become molecules

In dark nebulae (colder clouds of gas and dust)

Who first proposed the idea of the birth of stars?

Immanuel Kant

Which stars are born most quickly?

Heavier stars

What are the early steps in the growth of a star

• As the original cloud collapses, the cloud’s temperature gets hotter;

• 99% of the cloud material gets to the center and begins to resemble a protostar (center is about 1,000,000* K)

What happens to the spin of a cloud after it collapses?

The cloud spins faster.

What happens as a result of increased cloud spin during the birth of a star?

The cloud flattens into a disk shape, called a proplanetary disk.

What are the later steps in the growth of a star

• Nuclear fusion begins in its core once it reaches the appropriate, hot, temperature;

• Fusion causes energy to flow out, providing outward pressure as it flows;

• The star is no longer being shrunk by gravity, making it a “real star”

Why are Brown Dwarfs considered “failed stars”?

Their masses are too light, making the temperature inside too cold to perform nuclear reactions.

How do protoplanets start to form?

• Grains/clumps of dust cling to each other by the electromagnetic force, creating clumps of dust called planetesimals;

• Once the planetesimals gain mass, their gravity increases, causing mass to be added on at a faster rate (accretion);

• Gravity makes the planetesimals rounder, forming protoplanets

Why did planets nearest to the sun not grow large?

• There was less material for them to scoop up in their shorter paths;

• The temperature was too hot meaning that material was not solid, preventing growth (planets need solid materials to grow large)

How did outer planets, like Jupiter & Saturn, grow to be so huge?

• There was more material in their longer paths;

• Many gases out there froze, creating solids which then fuel growth.

What caused the era of bombardment?

Outer layers of young planets turned solid, as well as planetesimals. These bodies collided a lot, leading to shattering and meteors flying everywhere, constantly striking planets and moons.

How was Mercury affected during the era of bombardment?

Some of its thin, outer layers were removed.

How was Mars affected during the era of bombardment?

Its northern parts were knocked off, and some of that debris made Mars’s 2 moons.

How was the Moon affected during the era of bombardment?

Material was ripped off of Earth, loose material clung back together to create the Moon.

What affected planets’s orbits, causing planetary migration after being born?

Planets pulled on each other;

Jupiter invaded the Asteroid Belt;

Uranus & Neptune invaded the Kuiper Belt

How did liquid water end up being on Earth?

Melted ice that came from comets and asteroids which were tossed around due to the gravity of invading planets.

What will happen when the Sun dies?

A Planetary Nebula will appear; A White Dwarf (remaining dead core of a star) will be seen