Topic 8 Flashcards
(21 cards)
Name each stage of the life cycle of a star.
-cloud of dust and gas nebula
-protostar
-main sequence star
-red super giant -red giant
-supernova -white dwarf
-neutron star -black hole -black dwarf
How many stars does our solar system have?
one star the sun
What is the solar system?
all the stuff that orbits our sun
What are planets?
large objects that orbit our sun
What is the moon?
a type of natural satellite
How is the sun formed?
The Sun was formed from a cloud of dust and gas (nebula) pulled together by gravitational attraction.
What does gravity provide?
the force that allows planets and satellites to maintain their circular orbits.
What does the planet, moon, comet, asteroid and artificial satellite orbit?
planet = sun
moon = planet
comet = sun
asteroid = sun
artificial satellite = any object or body in the solar system
What does it mean if an object in a circular orbit?
It is constantly changing direction, which means it’s constantly accelerating and changing velocity
Explain why an object can accelerate in a circular orbit.
For an object to accelerate there must be a force acting on it. This force is directed to the centre of the object. This force would cause the object to just fall towards whatever it was orbiting but as the object is already moving, it just causes it to change its direction. The object keeps accelerating towards what it’s orbiting but the instantaneous velocity (which is at a right angle to the acceleration) keeps it travelling in a circle. The force that makes this happen is provided by the gravitational force (gravity) between the planet and the sun or between the planet and its satellites.
What does the size of the orbit depend on?
the objects speed
How does the gravitational force affect the speed of the orbiting object?
The stronger the force, the faster the orbiting object needs to travel to remain in orbit
How does speed affect an object in a stable orbit?
if the speed of the object changes the size (radius)of its orbit must do so too. Faster moving objects will move in a stable orbit with a smaller radius than slower moving ones
What does the universe seem to be doing?
expanding as all its galaxies seem to be moving away from each other
What is the evidence that suggests the universe is expanding?
-when we look at light from most distant galaxies, we find that the wavelength has increased
-the wavelengths are longer than they should be - they’re shifted towards the red end of the spectrum. This is called a red-shift. This suggests the source of the light is moving away from us very quickly
How do scientists think the universe started?
with a big ban as all the galaxies are moving away from each other at great speed suggesting something must have got them going
Explain the big bang theory.
Initially, all the matter in the universe occupied a very small space. This tiny space was very dense and so was very hot. Then it exploded - space started expanding and the expansion is still going on
What new evidence might change our theory of the gig bang?
Observation of supernovae from 1998 appear to show that distant galaxies are moving away faster and faster
What is dark matter?
the name given to an unknown substance which holds galaxies together but does not emit any electromagnetic radiation
What is dark energy?
dark energy is thought to be responsible for the accelerated expansion of the universe but no one really knows what these things are
