Post on 30-Dec-2015
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The Sun and Other Stars
The Cone Nebula
The Sun is a large ball of gas
The surface layer of the Sun is called the photosphere It is about 6000 °C
Sunspots are dark areas of the sun where there is strong magnetic activity
Watching the movement of sunspots, scientist have discovered the Sun rotates It rotates faster at the equator than at the poles (doesn’t
rotate like the Earth or other planets do)
Features of the Sun
When magnetic fields explode and send out charged
particles into space
Solar wind – Fast-moving charged particles sent out by the Sun
Solar storms can cause damage to satellites and other electronic equipment on Earth
Can also result in auroras – charged particles from the Sun charge gases in the atmosphere and lead to different colours in the sky at the North and South Poles
Solar Flares
The Sun is needed for all life on Earth Solar energy causes the winds and ocean
currents It provides energy for photosynthesis and is
the main force behind all of earth’s weather and climate
The Sun sends out a lot of different types of energy like: Microwaves, radio waves, x-rays, gamma rays. The energy that reaches the surface of Earth
are as visible light and infrared radiation (heat)
Why is the Sun Important
Luminosity – A star’s total energy output per
second Some stars have been found that are more than
400,000 times more luminous than the Sun!!
Absolute magnitude – What magnitude we would observe the star to have if it was place 32.6 light-years from Earth The Sun would have an absolute magnitude of
4.7 (not very bright at all)
Other stars
Stars have different colours – blue, blue-white, yellow,
orange, red
The colour of the star can be used to guess the temperature of the star.
The Sun is yellow and is about 6000 C at the surface
Blue stars are hotter – up to 35,000 C at the surface
Red stars are colder – about 3300 C at the surface
Other stars
Binary stars are two stars that orbit each other
Star masses are measured in solar masses – The Sun is that standard and is 1 solar mass
Some stars are over 100 solar masses – this means that they are 100 times more massive than the Sun
A Hertzsprung-Russel (H-R) diagram – is a graph that compares stars colour and absolute magnitude or luminosity
The Mass of Stars
Main sequence – A band of stars on an H-R
diagram that runs diagonally from upper left (bright- hot stars) to lower right (dim, cool stars)
90% of all stars (including our Sun) are main sequence stars.
Star Classification
Stars may last for millions to billions of years,
but eventually their fuel runs out
Stars end up as either a white dwarf, a neutron star or a black hole when they run out of fuel
What they turn into depends on their starting mass
How stars Evolve
Low mass stars like red dwarfs have less mass
than the Sun
They take up to 100 billion years to burn up their hydrogen
When they run out of fuel, they become white dwarfs – small, dim and hot star
Low-mass stars
Like our Sun
Use up hydrogen in about 10 billion years
Core collapses (caves-in) when fuel is used up
Pressure increases and the star gets bigger
It becomes a red giant. The sun will become a red giant and will be as big as the orbit of Mars
Eventually they will shrink down to become a white dwarf
Intermediate-Mass Stars
Stars that are 12 or more solar masses
Use up there fuel much faster and therefore die much faster
Do to higher temperatures and pressures, are able to form heavier elements up to iron.
First they will expand to red supergiants
When the core collapses, an explosion is sent out called a supernova
Supernova’s blow off the outer part of the star and can be million of times brighter than the star was
High-mass Stars
All the iron in your blood came from supernovas!!
In fact most of the atoms that make up your body started in the stars at one time in the past!!
Supernovas were first discovered in 1987 by Canadian astronomer Ian Shelton from the University of Toronto
Did you know that…
If a star starts with a mass of 12-15 solar masses
it will become a neutron star after its supernova
If a star starts with a mass of more than 25 solar masses it will become a black hole
Neutron stars are about 20-30 km in diameter
Some neutron stars spin up to 30 times per second, these are called pulsars
Neutron stars and Black Holes
Black holes have so much mass and gravity that light cannot
escape.
Black holes were predicted to exist before they were even discovered
Since you can’t see a black hole, scientists look for gravitational effects caused by the black hole
Dr. Tom Bolton of the University of Toronto was the first person to identify a black hole in 1972.
Supermassive black holes are thought to exist at the center of every galaxy
Neutron stars and Black Holes
Newly discovered black hole is 17 billion times the mass of the sun, may be biggest ever found
Found in a small galaxy called NGC 1277 (one quarter the size of our Milky Way)
New Discovery