The Universe Flashcards
The Universe
all existing matter and space considered as a whole; the cosmos. Has been constantly expanding since the big bang 13 billion years ago.
The observable universe
The observable universe is the ball shaped part of the universe that contains all matter that can be seen or detected from earth
constellation
a group of stars forming a recognizable pattern that is traditionally named after its apparent form or identified with a mythological figure.
Galaxy
a system of millions or billions of stars, together with gas and dust, held together by gravitational attraction of a black hole
solar system
The solar system is made up of the sun and the 8 planet that orbit it
planet
a celestial body moving in an elliptical orbit round a star.
parsec
a unit of distance equal to 3.26156 light years
apparent magnitude
the brightness of an object relative to earth
star
A star is a luminous celestial body made up of hot gases, primarily hydrogen and helium, undergoing nuclear fusion to produce energy and light.
light year
A light year is the distance light would travel in a year
absolute magnitude
the brightness of an object at a distance from earth of 10 parsecs
speed of light
3.0 x 10^8 m/sec
The milky way galaxy
The milky way galaxy is large collection of gas, dust and billions of stars and their systems
Order of planets
Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, and Neptune
HR-diagram
The Hertzsprung-Russell (HR) diagram is a chart that plots stars by their brightness and temperature, showing how they change and evolve over time.
Stellar Evolution
Stellar evolution is the process by which a star changes over time, from its formation to its death
Nuclear Fusion
Nuclear fusion is the process where two light atomic nuclei combine to form a heavier nucleus, releasing energy
Super Nova
A supernova is a massive explosion that occurs at the end of a star’s life cycle, resulting from core collapse in a supergiant star
Planetary Nebula
A planetary nebula is a glowing shell of gas and dust ejected from a dying star, surrounding the remaining hot core after it has shed its outer layers.
White dwarf
A white dwarf is a small, dense remnant of a star that has exhausted its nuclear fuel and shed its outer layers, no longer undergoing fusion.
Neutron Star
A neutron star is an extremely dense remnant of a supernova explosion, composed mostly of neutrons and having a strong gravitational field.
Black Hole
A black hole is a region of spacetime with gravitational pull so strong that nothing, not even light, can escape from it, formed from the collapse of a massive star.
Luminosity
Luminosity is the total amount of energy emitted by a star per unit time, often expressed in watts or as a multiple of the Sun’s brightness.
Main Sequence
The main sequence is a continuous band of stars on the HR diagram where stars spend most of their life, fusing hydrogen into helium in their cores.
Black Dwarf
A black dwarf is a theoretical stellar remnant that occurs when a white dwarf has cooled sufficiently that it no longer emits significant heat or light, becoming effectively invisible.
How does nuclear fusion work in main sequence stars
Stars fuse hydrogen in their cores into helium
How does nuclear fusion work in red giants
stars fuse helium into heavier elements such as carbon and oxygen
How does nuclear fusion work in red super-giants
stars fuse helium into elements up to iron where
What causes a star to go from the main sequence to a red giant or super giant
Once a star runs out of hydrogen to fuse their core condenses, increasing temperature and pressure until they can fuse helium at which stage they become red giants or super giants
what causes a red giant or super giant to evolve
Once a red giant runs out of helium to fuse the core collapses and the outer layers are expelled. In a red super giant once iron is fused in the core it sets off a chain reaction resulting in a supernova.
What forces balance each other in stars
radiation pressure and gravity
What is the big bang theory
The Big Bang theory posits that the universe began from an extremely hot and dense state approximately 13.8 billion years ago and has been expanding ever since, leading to the formation of galaxies, stars, and cosmic structures.
What is the steady state theory
The steady state theory suggests that the universe is eternal and unchanging on a large scale, with new matter being continuously created as it expands, maintaining a constant density despite the growth in size.
What are the 6 stages of the Big Bang theory
Singularity, Inflation, Formation, Nucleosynthesis, Recombination, Formation of stars and galaxies
What are 3 pieces of evidence supporting the Big bang theory
CMBR, redshift of galaxies and abundance of light elements
What is CMBR
CMBR is the faint glow of radiation left from when the universe was just 380,000 years old
What is Redshift of galaxies (doppler effect)
The light coming from distant galaxies appearing redder because of longer wavelengths, showing that they are moving away from us
How does abundance of light elements support the big bang theory
Observations of light elements match predictions from nucleosynthesis models
Evidence for steady state theory
even distribution of galaxies throughout universe and universal expansion
How are the BBT and SST similar and different
Similar through offering ideas about the origins of the universe and different by start and end, density and amount of matter
what is the singularity, inflation and formation
The singularity is a point of infinite temperature and density.
The inflation a rapid expansion, stretching the universe faster than the speed of light within fractions of a second.
The formation is protons, neutrons and electrons being formed as the universe cooled
what are the nucleosynthesis, recombination and the formation of stars and galaxies
Nucleosynthesis is the formation of light elements.
The recombination is electrons combnining with nuclei to from neutral atoms after about 380,000 years, allowing light to travel freely.
The formation of stars and galaxies is gravity pulling matter together over millions of years to form more complex cosmic structures
