Astronomy Unti 3: The Stars

Constellation:

A group of stars that form an imaginary pattern in the night sky

Asterism:

A group of stars that isn’t a part of the 88 constellations

North Star:

A star that sits almost directly above the North Pole

Zenith:

The point where a celestial object is directly above the observer

Circumpolar:

Located near the pole of the Earth

Zodiac:

An imaginary belt in the sky that is divided into 12 sections, representing the 12 month of the year

Rotation:

The Earth rotating around it’s axis

Revolution:

The Earth orbiting the sun

Explain the statement: You are made of star dust

Every element in your body has is billions of years old, because every atom on Earth came from a star nursery at some point in time

How are elements up to iron created?

Stars fuse and create the lighter elements in their cores

What is unique about the fusion of iron?

The fusion of the lighter elements before iron are exothermic reactions, meaning that they release heat, while iron is an endothermic reaction when it undergoes fusion

How are heavy elements beyond iron created?

They are formed through supernova and the expolsions from violent stars through neutron capture

How is wavelength related to energy, temperature, and color in stars?

Hotter stars: short wavelengths, more energy, bluer light

Colder stars: long wavelengths, less energy, less light

How does the emission spectrum of a star change througout it’s evolution?

By shifting in overall temperature and color and altering spectral lines

What is the diference between apparent and absolute magnitude?

Apparent: how bright a star looks from Earth

Absolute: A star’s brightenss if it were placed 32.6 light years away

Why is a red giant so much more luminous than a yellow star?

It has a larger surface area that radiates more total energy even though it is less luminous

What defines a star?

It’s ability to generate immense energy through nuclear fusion

What causes the shift from protostar to a star on the main sequence?

When its core becomes hot and dense enough for sustained nuclear fusion

What causes the state of equilibrium in a main sequence star?

A perfect balance between inward gravity and outward thermal pressure

What is the difference between a planetary nebula and a solar nebula?

Planetary: A shell of gas from a sying star (end of life)

Solar: A cloud where planets are born (beginning of the star cycle)

What is the relationship between a planetary nebula and a white dwarf?

The are two stages in the death of a low to medium mass star

Why do some dying stars end in a white dwarf while others end in a neutron star or a black hole?

It’s based on their mass: low mass stars leave white dwarfs, while massive stars cuase black holes

Which star has the longest life span, and why?

Red dwarfs; low mass, slow hydrogen consumption

Stellar evolution of a low mass star:

1. Molecular cloud of gas and dust

2. Gravity collapse of gas and dust

3. Low mass main-sequence star

4. Planetary nebula

5. White dwarf

6. Black dwarf

Evolution of a medium mass star (sun):

1. Molecular cloud of gas and dust

2. Gravity collapse of gas and dust

3. Medium mass main-sequence star

4. Giant or supergiant

5. Planetary nebula

6. White dwarf

7. Black dwarf

Evolution of a high mass star:

1. Molecular cloud of gas and dust

2. Gravity collapse of gas and dust

3. High-class main-sequence star

4. Giant or supergiant

5. Supernova

6. Neutron star

Evolution of a massive star:

1. Molecular cloud of gas and dust

2. Gravity collapse of gas and dust

3. Very high mass main-sequence star

4. Giant or supergiant

5. Supernova

6. Black hole

Protostar:

Enough mass raises temperature and presure to star nuclear fusion

Star:

The heat from fusion and gravity cancel each other out (they are balanced)

Planetary Nebula:

The atmosphere of the star dissapating into space

White Dwarf:

It exhausts the nuclear fuel in it’s core that is needed to generate pressure

Main Sequence:

It is a low mass star that is fusing hydrogen that makes it cooler than other stars

Black Dwarfs:

All the heat disspates from the star

Supernova:

Too much mass from a companion star scatters elements out into space

Red supergiant:

Carbon and oxygen nuclei are created due to immense gravitaional collapse

Post supernova core remnant:

The star’s core has become so dense that it forms a black hole