Task 2 – Do stars live and die?

Where do stars come from?

a big cloud of dust and gas called a nebula (nebulae

is plural)

Named after the Latin word for “cloud”,A nebula can be many light years across. It is in these nebulae that dust and gas can come together to form stars. They are also often “stellar nurseries” – i.e. the place where stars are born First a protostar is “born” – it is formed as gravity begins to pull the gases together into a ball.

A star is not truly a star until it can fuse hydrogen into helium. Before that, they are called protostars.

Nebulae

Life Cycles of Stars

Life of a Star- what happens to a star depends on its mass

•All stars begin life when gas and dust in a nebula contract to form a protostar.

Life Cycle

It is called a cycle because it has predictable patterns that it goes through

Large stars follow the same path So do medium and smaller stars

Small star path:

Small Star (~1 solar mass) = nebula – protostar (begins to release energy)– (yellow) main sequence star (until it begins to run out of fuel) – red giant (helium core runs out, starts burning other elements) - planetary nebula – white dwarf (runs out of energy) – black dwarf

Note – planetary nebula is one of the stages of a star’s life cycle (don’t confuse it with the starting nebula). A planetary nebula is a ring-shaped nebula formed by an expanding shell of gas around an aging star.

Massive Star Path:

Massive Star (~10 solar masses) = nebula –protostar (begins to release energy) – blue main sequence star (until it begins to run out of fuel) –red supergiant (helium core collapses) - supernova

Last stage: If the core survives it becomes a neutron star (core of 1.5 -3 solar masses) or a black hole (core greater than 3 solar masses)

The next image shows the life cycles of both star “paths”

Watch the two videos now:

https://www.youtube.com/watch?v=4xIQGbYur9Q

The Life and Death of Stars Star Personalities

https://www.youtube.com/watch?v=2PO_jMgmLvs

This ends task 2 slides