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

Video

How Big is Our Sun Compared to 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