astrophysics Flashcards
What are the classifications of stars based on their color?
Stars can be classified into:
* Yellow stars
* Red dwarfs
* Blue giants
* Red supergiants
These classifications are based on the star’s color and surface temperature.
How does a star’s color relate to its temperature?
A star’s color is related to its surface temperature:
* Red stars are the coolest (around 3000 K)
* Blue stars are the hottest (around 30,000 K)
The color of a star indicates its temperature, with bluer stars being hotter.
What happens to a star’s color as it expands and contracts?
As a star expands, it cools and becomes redder; as it contracts, it heats up and becomes whiter.
This change is due to the relationship between temperature and color.
What are the initial stages of star formation?
The initial stages of star formation are:
* Nebula
* Protostar
* Main sequence star
All stars follow these stages as they begin to form.
What is a nebula in the context of star formation?
A nebula is a giant interstellar cloud of gas and dust from which stars form.
Nebulae are the starting point for the formation of stars.
What defines a protostar?
A protostar is a hot ball of gas that forms when gravity pulls particles closer together in a nebula.
The density and temperature of the protostar increase due to particle collisions.
What characterizes a main sequence star?
A main sequence star is defined by the initiation of nuclear fusion reactions in its core, achieving stability.
During this phase, the star is in equilibrium.
What are the evolutionary stages of a solar mass star after the main sequence?
The stages are:
* Red giant
* Planetary nebula
* White dwarf
This sequence describes the final life stages of a low-mass star like the Sun.
What occurs when a solar mass star becomes a red giant?
The star expands and cools as it begins to fuse helium after hydrogen fusion decreases.
This leads to the star’s outer layers expanding significantly.
What happens to a star after it becomes a white dwarf?
The white dwarf cools down over time, and the energy it emits decreases.
This marks the end of the star’s active life cycle.
What are the stages of a high-mass star after the main sequence?
The stages are:
* Red supergiant
* Supernova
* Neutron star (or black hole)
These stages differ significantly from those of lower mass stars.
What characterizes a red supergiant?
A red supergiant forms when a high-mass star begins to fuse helium and expands as hydrogen fusion decreases.
This stage is similar to the red giant phase but occurs in more massive stars.
What is a supernova?
A supernova is a gigantic explosion that occurs when the fusion reactions in a red supergiant cannot continue, causing core collapse.
This event ejects the star’s outer remnants into space.
What forms at the center of a supernova explosion?
A neutron star forms at the center of a supernova explosion.
If the star is massive enough, it may continue collapsing to form a black hole.
What is a black hole?
A black hole is an extremely dense point in space from which not even light can escape.
Black holes are formed from the remnants of massive stars after a supernova.
Fill in the blank: The life cycle of a solar mass star ends with a _______.
white dwarf
This marks the final stage of a low-mass star’s life cycle.
True or False: A lower mass star fuses helium into heavier elements like iron.
False
A lower mass star fuses helium into light elements, whereas a higher mass star can fuse it into heavier elements.
What is the definition of the Universe?
A large collection of billions of galaxies and the entirety of space.
The Universe encompasses all known matter, energy, planets, stars, galaxies, and the contents of intergalactic space.
What is a galaxy?
A large collection of billions of stars.
Examples include the Milky Way, Andromeda, and various other galaxies.
What is the position of the Sun in our Solar System?
At the centre of our Solar System.
The Sun is a star that provides light and heat to the planets orbiting it.
How many planets are in our Solar System?
Eight planets.
The eight planets are Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, and Neptune.
What affects an object’s weight on different planets?
Gravitational field strength.
Weight is the force acting on an object due to gravitational attraction.
What is the approximate gravitational field strength (g) on Earth?
10 N/kg.
This value indicates the force of gravity acting on a 1 kg mass.
What is the relationship between mass and weight on different planets?
Mass remains constant, but weight changes depending on gravitational field strength.
An object’s weight will vary significantly on different planets, especially gas giants.
What is orbital motion?
The movement of bodies in space around larger bodies due to gravitational attraction.
This includes planets orbiting the Sun, moons orbiting planets, comets, and artificial satellites.
What shape are the orbits of planets around the Sun?
Slightly elliptical (stretched circles).
All planets orbit in the same plane and travel in the same direction.
What happens to a planet’s orbital speed as its distance from the Sun increases?
It decreases.
Planets closer to the Sun travel faster in their orbits.
How do the orbits of comets differ from those of planets?
Comets have highly elliptical or hyperbolic orbits.
This leads to significant changes in speed as their distance from the Sun changes.
What is the definition of orbital period?
The time taken for an object to complete one orbit.
Orbital period is crucial for understanding the motion of celestial bodies.
What is the formula for average orbital speed?
v = 2πr / T, where v is orbital speed, r is average radius, and T is orbital period.
This equation allows for the calculation of speed based on orbital radius and time.
Fill in the blank: The gravitational force of attraction causes the Moon to orbit around the _______.
Earth.
The gravitational attraction between the Earth and the Moon is what keeps the Moon in orbit.
What is the effect of gravitational field strength on weight?
Higher gravitational field strength results in greater weight.
This is evident when comparing weights on Earth and Jupiter.
True or False: The orbits of moons are always circular.
False.
While many moons have circular orbits, some may have elliptical paths.
What is the relationship between orbital radius and orbital speed?
The greater the orbital radius, the slower the orbital speed.
This is due to the gravitational effects of the Sun.
What is the gravitational field strength on the Moon compared to Earth?
Less than on Earth.
This makes lifting objects easier on the Moon than on Earth.
