Quiz 2 (4-6)

Question 1

What is a galaxy?

Answer 1

HUGE group of stars, gas and dust held together with gravity. There may be many billion galaxies and each contain billions of stars. 100-1000 light years across.

Question 2

What is the closest spiral galaxy to ours?

Answer 2

Andromeda Galaxy. It is 2.5 million light years away.

Question 3

What is a nebula?

Answer 3

a cloud of dust, gas and stars. Smaller than galaxies, approximately 10-100 light years across.

Question 4

What are the 4 types of galaxies?

Answer 4

spiral, elliptical, barred spiral and irregular

Question 5

What are spiral galaxies?

Answer 5

contain gas, dust and many bright stars. Looks like a pinwheel, they are relatively flat with a central bulge and 2-4 rotating arms. These account for majority of the galaxies we have observed.

Question 6

What are barred spiral galaxies?

Answer 6

Similar to spiral, except with central bar with spiral arms extending from bar.

Question 7

What are Elliptical Galaxies?

Answer 7

Contains very little gas or dust and older reddish stars. Looks like flat circles, can be a perfect circle or oval and account for 20% of galaxies we have observed.

Question 8

What are irregular galaxies?

Answer 8

Contains mostly gas, dust and few stars. They have no definite shape and account for about 10% of galaxies observed.

Question 9

What is the milky way?

Answer 9

The milky way is a barred spiral galaxy and is about 100000 light years in diameter. There is a central bulge surrounded by 4 large spiral arms. It is constantly rotating, our sun travels with galaxy at 800000 km/hr (it would take 230 million years to travel one rotation of galaxy). Surrounded by a gas halo, that is also rotating. Contains 200 billion stars. Our solar system is one of spiral arms. Giant black hope in the center, billions times larger than the sun.

Question 10

How old is our sun?

Answer 10

our sun was born 4.5 billion years ago, is it young compared to over half the stars in our galaxy (10bya)

Question 11

What is a black hole?

Answer 11

A black hole is a area of space that has no volume but has a very large amount of mass. It is formed when a supernova star collapses and the force of gravity forms a hole. Nothing can escape, not even light. We cannot see them, we only see the effects of the gravitational force that comes from an object with mass and size. They are found by looking for areas where dust, gas and stars disappear.

Question 12

What and when was the first image of a black hole?

Answer 12

Taken on April 10, 2019. This is 87.55 million light years away.

Question 13

What do all galaxies have in common?

Answer 13

Contain a large amount of gas and dust. They are held together by gravity and is surrounded by aa gas halo.

Question 14

What do spiral and irregular galaxies have in common?

Answer 14

contain young and bright stars

Question 15

What do elliptical and irregular galaxies have in common?

Answer 15

contain older reddish and dull stars.

Question 16

What is a light year?

Answer 16

1 light year is 1.5 trillion kilometer. Keeps track of distances outside of our solar ystem

Question 17

How do stars form?

Answer 17

1. Nebulae: Stars form in a nebula
2. Protostar: Gravity pulls matter together into a spinning ball
3. Nuclear Fusion: The core increases in temperature and pressure until it ignites, creating a burning ball of gas

Question 18

What is a star?

Answer 18

giant burning sphere of gases, mostly hydrogen molecules combines to form helium. Nuclear fusion reaction releases large amounts of heat, radiation and light energy

Question 19

Where does nuclear fusion occur?

Answer 19

In the core of a star. Stars continue to burn as there is hydrogen to fuel nuclear fusion. As a star runs out of hydrogen, helium combines to form new elements

Question 20

How does a star get its energy to glow?

Answer 20

dusion of hydrogen into hellium, called a nuclear reaction

Question 21

What elements make up young stars?

Answer 21

70% hydrogen and 30% helium (1-10% other elements)

Question 22

What causes a star to become a supernova?

Answer 22

the star begins to run low on hydrogen and fuses other elements together until it is heavier (more dense) elements that destabilize the core of the star than it explodes

Question 23

Why do you think it takes a tremendous amount of heat and pressure to create helium (and later carbon..)

Answer 23

heat makes particles move faster, pressure forces nucleus of atoms together

Question 24

What could you infer about the age of a star if you were to find evidence of iron being present?

Answer 24

Run out of hydrogen and it fusing heavier elements. When iron is present it shows that it is near the end of the stars life.

Question 25

What are the 2 paths a star can take after nuclear fusion?

Answer 25

low mass and high mass stars

Question 26

What are low mass stars?

Answer 26

sun like stars, are stabe and long lived (billions of years)

Question 27

What is the path of a low mass star?

Answer 27

low mass star to red giant to white dwarf star to black dwarf star

Question 28

What are white dwarf stars?

Answer 28

stars slowly burn out and cool down overtime, releasing matter and gas into space. Eventually remaining core becomes white dwarf star

Question 29

What is a black dwarf star?

Answer 29

A white dwarf star turns into a brown dwarf star than once cooled completely they become a black dwarf star

Question 30

What is the path of a high mass star?

Answer 30

high mass star to red supergiant, to supernova to neutron star or black hole

Question 31

What are high mass stars?

Answer 31

are unstable and short lived (thousands or millions of years)

Question 32

What are red supergiant?

Answer 32

when high mass stars run out of fuel and cool down and expand they become red supergiants

Question 33

how does a red supergiant turn to a supernova?

Answer 33

they collapse into itself and result in a huge explosion called a supernova. From these conditions we get fusion of all remaining elements

Question 34

how do supernovas turn to neutron stars?

Answer 34

the core becomes very compacted during an explosion and forms a small super-dense rapidly spinning object called a neutron star

Question 35

how does a supernova turn to a black hole?

Answer 35

if there is enough mass than the high pressure of the supernova can form a black hole

Question 36

How do we classify stars?

Answer 36

using observable characteristics
1. size
2. luminosity (amount of light emitted
3. colour (based on temperature)

Question 37

How do we use size to classify stars?

Answer 37

compare the size of other stars to our sun, Bigger size does not always mean more mass

Question 38

How do we use luminosity to classify stars?

Answer 38

a stars luminosity is the measure of total amount of light energy it gives off, per second, Less surface area means less luminous, more surface are is more luminous

Question 39

How do we use color to classify stars?

Answer 39

the color of a star relates to its temperature, the color of the burning gas (the amount of heat) The cooler the more red it appears, the hotter the more blue it appears

Question 40

What are the star color classes?

Answer 40

class o - dark blue
class b - medium blue
class a - light blue
class f - white
class g- yellow
class k - orange
class m - red

Question 41

What spectral class does our sun belong to?

Answer 41

G as our sun is yellow, therefore it is 5500 - 6000k

Question 42

What is the Hertzsprung Russell diagram

Answer 42

The HR diagram categorizes stars based on their observable characteristics. y axis - luminosity
x axis - color (temperature)

Question 43

In the HR diagram which group includes our sun?

Answer 43

main sequence

Question 44

What are the characteristics of our sun on the HR diagram?

Answer 44

1Lsun, about 6000k and yellow

Question 45

What is the most luminous category on the HR diagram?

Answer 45

blue giants, red supergiant’s. More luminous due to their larger size and therefore more surface are to emit light

Question 46

What is the emission spectra?

Answer 46

produced when a hot gas glows giving off light

Question 47

What is the absorption spectra?

Answer 47

produced when lite light is shone through a tube of gas which absorbs some of the light. dark lines appear where certain color of spectrum are missing, they correspond to a particular element which is burned and consumed by the star