The Universe

Question 1

What is gravity?

Answer 1

Gravity is one of the fundamental forces and one of the weakest. It is the attraction between the center of two objects.

Question 2

What is a star?

Answer 2

A self-luminous spheroid celestial body that produces energy by means of nuclear fusion reactions.

Question 3

What is a nebula?

Answer 3

An interstellar cloud of dust, hydrogen, helium, and other ionized gases.

Question 4

What is absolute magnitude?

Answer 4

The measure of the luminosity of a celestial object at a standard distance of 10 parsecs.

Question 5

What is apparent magnitude?

Answer 5

The measure of the luminosity of a celestial object as seen from the earth.

Question 6

What is a black hole?

Answer 6

When a star more than about 20 times the mass of the sun ages, it will be unable to become a neutron star due to its mass and will result in the star collapsing forever. Gravity in this part of spacetime is so strong here that nothing, including electromagnetic radiation, can escape it.

Question 7

What is stellar parallax?

Answer 7

The apparent shift in the position of a nearby star against the background of distant objects.

Question 8

What is a neutron star?

Answer 8

When a star about 8 to 20 times the mass of the sun begins to age, the core begins to collapse and electrons and protons in the core merge to become neutrons. The pressure applied on the neutrons as they are being squeezed creates a pressure that halts the collapse of the core.

Question 9

What is a light-year?

Answer 9

A unit used to measure distances in space. The distance that light travels in one year. Equal to 5.8 trillion miles (~300,000 km/s).

Question 10

What is hydrogen burning?

Answer 10

Hydrogen burning is when four hydrogen nuclei fuse into a single helium nucleus with four two protons and two neutrons.

Question 11

What is luminosity?

Answer 11

The absolute measure of a radiated electromagnetic power emitted by a light-emitting object.

Question 12

What is an Hertzsprung-Russell (H-R) diagram?

Answer 12

A scatter plot showing the relationship between the stars’ absolute magnitudes versus their temperatures.

Question 13

What is main sequence?

Answer 13

A continuous and distinctive band of stars that appears on H-R diagrams. Main sequence stars are any star that is fusing hydrogen in its core and has a stable balance of outward pressure from nuclear fusion and gravitational forces.

Question 14

What are supergiant stars?

Answer 14

Some of the most massive and luminous stars. Occupy the top region of the H-R diagram. Absolute visual magnitudes of -3 to -8. Temperature ranges from about 3,400 K to over 20,000 K.

Question 15

What are giant stars?

Answer 15

Stars with substantially larger radii and luminosities than main-sequence stars on an H-R diagram. Found above the main-sequence stars.

Question 16

What is fusion?

Answer 16

A process in which two or more atomic nuclei are combined to form one or more different atomic nuclei and subatomic particles.

Question 17

What is a proton-proton chain?

Answer 17

Also known as hydrogen burning. A chain where stars convert hydrogen to helium.

Question 18

What is electromagnetic radiation?

Answer 18

The waves of the electromagnetic field, propagating through space, carrying electromagnetic radiant energy. Solar energy.

Question 19

What is an isotope?

Answer 19

Variants of a particular chemical element that differ in neutron numbers.

Question 20

What is nuclear reaction?

Answer 20

A change in the characteristics of an atomic nucleus due to a collision with an energetic particle.

Question 21

What is a positron?

Answer 21

Also an antielectron. Has the same mass as an electron and a charge numerically equal to an electron but positive.

Question 22

What is nucleosynthesis?

Answer 22

The process that forms atoms more complex than the hydrogen atom.

Question 23

What is a white dwarf?

Answer 23

When a star the size of Earth energy production ends, the outer layer expands and are driven off by pulsations developed in the outer layers and causes a planetary nebula. At the center of this planetary nebula is a white dwarf made entirely of carbon.

Question 24

What are the phases of the Big Bang?

Answer 24

Big Bang Era, Planck Era, Grand Unification Era, Inflation Era, Electroweak Era, Heavy Particle Era, Light Particle Era, Nucleosynthesis Era, Recombination Era, Galaxy Formation Era, and Current Era.

Question 25

Describe the Big Bang Era.

Answer 25

From 0-10^-43 seconds and infinite temperature. Infinitely small and dense. Only one force existed: “superforce”/”supergravity”

Question 26

Describe the Planck Era.

Answer 26

From 10^-43 seconds with 10^32 °C temperature. Earliest time known to man. Two forces exist: gravity and grand unification.

Question 27

Describe the Grand Unification Era.

Answer 27

From 10^-35 seconds with 10^27 °C temperature. Three forces exist: gravity, strong nuclear, and electroweak. Quarks and leptons form.

Question 28

Describe the Inflation Era.

Answer 28

From 10^-32 seconds with 10^27 °C temperature. Size of the universe increases by a factor of 10^30 to 10^40.

Question 29

Describe the Electroweak Era.

Answer 29

From 10^-12 seconds with 10^15 °C temperature. Four forces: gravity, electromagnetic, strong electric, and electroweak) Neutrons and protons start forming quarks.

Question 30

Describe the Heavy Particle Era.

Answer 30

From 10^-7 seconds with 10^14 °C temperature. Proton and neutron formation in full swing.

Question 31

Describe the Light Particle Era.

Answer 31

From 10^-4 seconds with 10^12 °C temp. Electrons and positrons begin to form.

Question 32

Describe the Nucleosynthesis Era.

Answer 32

From 200 seconds with 10^12 °C temp. Helium, deuterium, and other lighter elements form; temperature too low to form heavier elements.

Question 33

Describe the Recombination Era.

Answer 33

From 300,000 years with 3,000 °C temp. Matter and radiation separate (atoms form).

Question 34

Describe the Galaxy Formation Era.

Answer 34

From 100-500 million years. -263 °C temp. Earliest star were created 100 million years ago. Oldest galaxies 500 million years.

Question 35

Describe the Current Era.

Answer 35

-270 °C temp. The universe is still expanding.

Question 36

What evidence supports the Big Bang Theory?

Answer 36

Hubble’s law (galaxies are moving away from each other), Cosmic Microwave Background Radiation (amount of heat left after Big Bang, travelling for 13.8-14 billion years), quasars (only found 10-13 billion light years away), radioactive decay, stellar evolution, and the speed of light (furthest stars are 10-13 billion light years away).

Question 37

What are the forms of electromagnetic radiation?

Answer 37

Radio waves, microwaves, infrared radiation, visible light, ultraviolet light, x-rays, and gamma rays.

Question 38

What are the different types of galaxies?

Answer 38

Spiral (and barred) galaxies, elliptical galaxies, and irregular galaxies.

Question 39

How do stars synthesize elements until iron?

Answer 39

Hydrogen to helium to carbon to oxygen to neon to magnesium to silicon and to iron.

Question 40

How is an H-R diagram arranged?

Answer 40

The y axis shows luminosity (from least to greatest and x axis shows temperature (from greatest to least). White dwarfs are found in the bottom left of the diagram, supergiants in the top right with giants just under it, and main sequence stars form a diagonal(ish) line from top left corner to bottom right corner.

Question 41

What are the characteristics of stars?

Answer 41

Stellar brightness (magnitude), distance, temperature and color (Blue stars: over 3,000 °C, hot. Red stars: below 3,000 °C, cool. Yellow stars: between 5,000 °C and 6,000 °C).

Question 42

What is the birth of a star?

Answer 42

Gravity contracts nebulae to form protostar. Temperatures rise. Long wavelength light is radiated.

Question 43

What is a star’s protostar stage?

Answer 43

Core reaches 10 million °C. Hydrogen nuclei fuse (hydrogen burning). Energy is released. Outward pressure increases and then is balanced by gravity.

Question 44

What is a star’s main-sequence stage?

Answer 44

90% of a star’s life. Star is stable. Stars age at different rates depending on size (Bigger stars die faster than smaller stars).

Question 45

What is a star’s red giant stage?

Answer 45

Hydrogen migrates outwards. Star’s outer envelope expands. Surface cools. Surface becomes red. Core collapses, helium becomes carbon. All nuclear fuel is used. Gravity squeezes star.

Question 46

What is a star’s burnout/death stage?

Answer 46

For a star the mass the size of the sun, the star will become a white dwarf. A star 8-20 times the mass of the sun will supernova and be left with a neutron star. A star with more than 20 times the mass of the sun will collapse forever and become a blackhole.

Question 47

True or false: We see because light brightens things.

Answer 47

True. We see due to the reflection of visible light on objects.

Question 48

True or false: Radioactive elements decay at a constant rate.

Answer 48

True.

Question 49

What does the luminosity of a star depend on?

Answer 49

A star’s temperature and radius. L=R^2(T^4).

Question 50

What does the luminosity of a star depend on?

Answer 50

A star’s temperature and radius. L=R^2(T^4).

Question 51

What are misconceptions with the Big Bang?

Answer 51

1. The sun is not a star.
2. The sun disappears at night.
3. The sun will never burn out.
4. The Earth is the largest object in the solar system.
5. The Earth is flat.
6. Gravity acts different from matter to matter.
7. Theories need to explain themselves.
8. Gravity needs a medium.
9. There is no evidence for the Big Bang.
10. The universe is static.
11. All the stars in a constellation are near each other.
12. All stars are the same distance from Earth.
13. The galaxy is crowded.
14. Stars are distributed evenly throughout the galaxy.
15. All stars are the same size.
16. A star’s luminosity depends solely on its distance from the Earth.
17. The patterns in a constellation are clearly defined.
18. There is a definite up and down in space.