Topic 8 - Space Flashcards
What is a satellite?
they orbit a planet - can be natural or artificial
What is an asteroid?
a small rocky object that orbits the sun
Where does the asteroid belt lie?
between Mars and Jupiter
(between the rocky and gas planets)
What is a comet?
made of ice and dust and have a very elliptical orbit around the sun
What is a galaxy?
a massive collection of billions of stars
What is the universe?
contains lots of galaxies and is mostly empty space
Describe a nebula
a giant cloud of hydrogen gas and dust - the first stage of a star
How does a nebula form a protostar?
the force of gravity pulls the particles closer together until it forms a hot ball of gas (protostar)
How does a protostar form a main sequence star?
- it continues to pull particles in which increases the density and temperature
- this means more nuclear fusion will occur and it will become a main sequence star
Why does a main sequence star remain stable for a long time?
the outward pressure force (from fusion reactions) is equal to the inward force due to gravity
How does a red giant become a white dwarf?
- the star becomes unstable and ejects the outer layer of dust and gas (called a planetary nebula)
- the core collapses (due to gravity) and it’s a white dwarf
How does a main sequence star become a red (super) giant?
- the star runs out of hydrogen so there are fewer fusion reactions
- the core shrinks because the inward gravity force is now stronger than the outward force
- fusion begins again and causes the outer part of the star to expand
How does a white dwarf become a black dwarf?
the white dwarf is emitting lots of energy (light) and becomes cooler and darker and becomes a black dwarf
How does a red super giant become a supernova?
once the fusion reactions finish, the core collapses suddenly, causing a huge explosion - called a supernova
How does a supernova become a neutron star / a black hole?
- a dense neutron star will form in a supernova
- if the star is massive, the neutron star will continue to collapse (due to gravity) and forms a black hole
Which main sequence stars become red giants and which become red super giants?
- small/ medium (sun size) - red giant
- big (bigger than sun) - red super giant
What is the complete life cycle of a star that’s a similar size to the sun?
- nebula
- protostar
- main sequence star
- red giant
- white dwarf
- black dwarf
What is the complete life cycle of a star that’s bigger than the sun?
- nebula
- protostar
- main sequence star
- red super giant
- supernova
- neutron star / black hole
What elements are formed in the fusion reaction in a main sequence star?
hydrogen nuclei fuse to form helium nuclei
What elements are formed in fusion reactions in red (super) giants?
helium nuclei will fuse to form elements lighter than iron
What elements are formed in fusion reactions in supernovas?
forms elements heavier than iron
Define an orbit
the curved path of one celestial object around another celestial object
What are the 2 forces acting on Earth when it’s orbiting the sun?
- gravity (pulling towards the sun)
- instantaneous velocity (moving forward)
Why is the earth constantly accelerating?
- it has a circular orbit so it’s constantly changing direction
- this means it’s velocity is constantly changing
- changing velocity = acceleration
Which planets travel at the fastest speeds?
the planets with a smaller orbit travel at the fastest speed because gravity is stronger so the speed must be faster so the planet can continue in it’s orbit
Describe how red shift works
- when light from the sun reaches the earth, certain wavelengths are missing
- light from other galaxies also have missing wavelengths, but shifted towards the red end of the spectrum (light waves get stretched as they travel to Earth)
- this indicates galaxies are moving away from us
The further away a galaxy is …
the faster it’s moving away from us
Why specifically are galaxies moving away from us?
the space between us and the galaxy is expanding
Describe the big bang theory
- around 14 billion years ago, all the matter was in a very small, dense region
- series of explosions, called the Big Bang
- caused the universe to expand, and it continues to do so
How is redshift evidence for the Big Bang?
- redshift proves that galaxies are moving further away from each other (because the light waves are stretched)
- proves the universe is expanding and if it’s expanding, it must’ve started very small
