Science B - The Universe Flashcards
(34 cards)
Approx. age of the universe
13.8 billion years old
Approx. size of the universe
93 billion light years in diameter
What’s a galaxy
Galaxies are gravitationally bound systems of stars, interstellar gas, dust, and dark matter. Their formation is attributed to early density fluctuations in the universe post-Big Bang, which led to regions of higher matter concentration. The Hubble classification system categorizes galaxies based on morphology:
What’s a star
Stars are self-luminous spheroids composed of hot gas undergoing nuclear fusion with hydrogen and helium.
What’s a solar system
A solar system consists of a central star and objects gravitationally bound to it.
What’s a stellar nebula
Nebulae are interstellar clouds of gas and dust playing critical roles in star formation.
Types of galaxies
Spiral Galaxies: Contain rotating disk structures with spiral arms, shaped Example: Milky Way.
Elliptical Galaxies: Spherical or elongated structures with older stellar populations and minimal interstellar medium, formed through galactic mergers.
Irregular Galaxies: Lack defined structure, often distorted by gravitational interactions.
Lifecycle of medium sized stars
Nebula > Protostar > Main sequence > Red giant > Planetary Nebula > White dwarf > Black Dwarf
Life cycle of high mass stars
Nebula > Protostar > red supergiant > Supernova
/. \
Neutron star. Black hole
What’s where on the Hertzsprung- Russel Diagram
Blue giants - top left
Red supergiant - right top
main sequence - diagonally down
red giant - bellow red super giant
white dwarf - bottom left
Order of the big bang theory
Big bang
inflation
inflation ends
protons form
nuclear fusion begins
nuclear fusion ends
CMG
First stars and galaxies form
Present day
4 lines of evidence to support the big bang theory
Redshift & Doppler Effect: The observed redshift of distant galaxies indicates that the universe is expanding. According to the Doppler effect, light waves from receding galaxies stretch, shifting toward longer (red) wavelengths. This was first noted in Hubble’s Law, which states that galaxies farther away exhibit greater redshift, reinforcing the idea of an initial expansion.
Cosmic Microwave Background Radiation (CMBR): This is faint thermal radiation left over from the early universe, detected as uniform microwave signals across space. Predicted by Big Bang nucleosynthesis, the CMBR represents the cooling remnants of the initial explosion
Hydrogen-Helium Ratios: Explains the relative abundance of light elements. Big Bang calculations predict a universe where hydrogen (~75%) and helium (~25%) formed shortly after the event. This distribution matches observations, confirming early fusion processes during the universe’s infancy.
Existence of Superheavy Elements: Elements heavier than iron require extreme conditions, such as those found in supernova explosions or neutron star collisions. The presence of these elements supports a universe that evolved from simple hydrogen-helium into complex atomic structures over billions of years.
What’s a coasting universe theory model
Assumes the rate of expansion remains constant over time, meaning no significant gravitational deceleration or acceleration.
The universe expands due to the momentum of the initial Big Bang, but gravity and dark energy effectively cancel out.
This corresponds to a flat, zero-energy-density universe where space expands at a steady pace indefinitely.
continues forever
What’s the decellerating model
Gravity from mass in the universe works against the expansion, gradually slowing it down.
If mass density exceeds a critical threshold, the universe could eventually stop expanding and collapse into a Big Crunch.
What’s accelerating model?
The dominant model today, supported by observational evidence.
Expansion speeds up due to dark energy, an unknown force driving space outward.
Matches findings from CMBR, supernova redshift data
Implies an indefinite expansion where galaxies move farther apart at increasing rates, leading to a cold, empty universe
Identify the purpose of Microwave, IR and radio-telescopes in terms of observing energy in the universe with an example of each
Microwave Telescopes: Detect cosmic microwave background radiation (CMBR), providing insights into the early universe and Big Bang remnants.
Wilkinson Microwave Anisotropy Probe (WMAP) – Mapped CMBR to refine Big Bang models.
Infrared (IR) Telescopes: Observe cooler objects like nebulae, exoplanets, and dust clouds, revealing star formation and planetary systems.
James Webb Space Telescope (JWST) – Studies exoplanets, star formation, and distant galaxies using infrared imaging.
Radio Telescopes: Capture radio waves emitted by pulsars, quasars, and interstellar gas, helping study cosmic magnetic fields and distant galaxies.
Square Kilometre Array
How does a spectroscope work?
A spectroscope separates light into different wavelengths, revealing the composition of celestial objects.
Identify the purpose of a spectroscope in terms of collecting information about the universe
Identifies the chemical makeup of stars, nebulae
Spectral lines reveal a star’s temperature and atmospheric conditions.
Doppler shifts in spectral lines indicate motion, supporting the study of galaxy redshifts and universe expansion.
Tracks nuclear reactions and cosmic processes over time.
Define an Astronomical Unit
AU = distance from the Earth to the Sun (150 million kilometers)
define light year
ly = the distance light
travels in one year (9.5 trillion km)
define parsec
pc = 3.262 light-years
Define gravity
the force of attraction between any two objects. gravity is a weak force and that the strength of the
force of gravity depends on the masses of the two objects and the
distance between them ALL objects attract each other
Formula for force
f = gravity (mass1 x mass 2)
————————-
distance between centre of both objects squared
f = force in newtons
g = gravity 6.673 x 10^-11 N m^2/kg^2
m1 and m2 = kg
r^2 = metres
Geocentric and heliocentric
geocentric - Proposed by Claudius Ptolemy (~2nd century CE).
Earth is motionless at the center of the universe.
heliocentric - Proposed by Nicolaus Copernicus (~16th century CE).
The Sun is at the center, and planets, including Earth, orbit it.
