topic 8- space physics

What are the six stages of a star about the size of the sun

Nebula, protostar, main sequence star, red giant, white dwarf, black dwarf

What are the six stages of a star much larger than the sun

Nebula, protostar, main sequence star, red super giant, supernova, neutron star or black hole

Describe the formation of stars

Stars initially form from clouds of dust and gas (nebula). Overtime the force of gravity pulls the dust and gas tightly to form a protostar. Within the protostar gravity causes particles to collide more frequently increasing the temperature when the temperature is high enough nuclear fusion begins to form helium nuclei. This gives out huge amounts of energy which keeps the core of the star hot. At this point we call it an actual star

Describe the main sequence star stage in a star

Outward pressure caused by energy being released by nuclear fusion is balanced by the inward pressure caused by gravity allowing for a long stable period which can last for billions of years

What happens when hydrogen eventually begins to run out

The fusion of helium ceases and so inward pressure of gravity takes over and contracts star until it’s so hot and dense nuclear fusion can start again causing it to expand. The nuclear fusion will form heavier elements up to iron

What happens after the main sequence star for stars about the size of the sun

Will expand into a red giant. It will then become unstable and expel its outer layers or dust and gas. This leaves behind a hot dense solid core called a white dwarf which doesn’t do any nuclear fusion. Overtime the white dwarf gets colder and darker as it emits all of its energy until it finally transitions to a black dwarf

What happens after the main sequence star for stars larger than the size of the sun

Expand into red giants where they expand and contract several times forming elements as heavy and iron. They eventually run out of elements to fuse and become unstable. They explode in a supernova forming elements heavier than iron that gets ejected alll across the universe. The exploding supernova throws outer layers of dust and gas into space leaving behind a very dense core called a neutron star. If star is big enough it will collapse into itself to become a black hole

What is a satellite

Objects that orbits planets. Can be natural eg moon or artificial eg artificial satellites

What is a planet

Large objects which orbit a star, their gravity has to be strong enough to have pulled in any nearby objects apart from their natural satellites

What is a dwarf planet

Planet liked objects that orbit stars

What are asteroids

Made mostly of rock and metal and found mainly in the asteroid belt (Between mars and Jupiter)

What is a comet

Made mostly of ice and dust and have more elliptical orbits

What is a galaxy

Massive collections of billions of stars most of which that have their own solar systems

What is the universe

Vast expanse of mostly empty space scattered with galaxies

What is an orbit

The curved path of one celestial object or spacecraft around another celestial object

What is an object (with forces)

The balance between the force providing the acceleration and the forward motion (instantaneous velocity) of the object

How does an orbit work

The object keeps accelerating towards the what it’s orbiting but the instantaneous velocity (which is at right angles to the acceleration and the force of gravity) keeps it travelling in a circle

Where is the force always towards

The centre of the circle

What does the size of an orbit depend on

The objects speed

The smaller the objects orbit…

The faster the object

What is the red shift theory

When we analyse light from distant galaxies we find that its wavelength has increased (it’s shifted towards the red end of the spectrum)

When does red shift occur

When the source of light is moving away from observer

Why do the light waves travelling towards us get stretched

Because the space between us and distant galaxies which is emitting the light is expanding

Some of the chemicals in the suns atmosphere…

…absorbs certain wavelengths of light

The further away a galaxy is…

…the more quickly it appears to be moving

What is the evidence that the universe use expanding

More distant galaxies have a great red shift than nearer ones this means more distant galaxies are moving away faster than the nearer ones so all the galaxies are moving away from each other, so the whole universe is expanding

Explain the Big bang theory

Initially all the matter in the universe occupied a very small space which was very dense and hot, then it exploded which caused space to start expanding which it still is

What is the most generally accepted theory of how the universe began

Big bang theory

What supports the Big Bang theory

Red shift measurements