Physics 8.1.5 Flashcards
What are the Stages in the Lifecycle of a ‘Large Star’? Explain each Stage. (6)
-Nebula: Giant Cloud of Hydrogen Gas & Dust.
-Protostar: The Centre of the Nebula Pulls all of the Hydrogen Gas & Dust in via the Inwards Force of Gravity, until it Forms a Hot Ball of Gas: the Protostar.
As the P.cles are Pulled Closer Together, the Density of the Protostar Increases.
So more Frequent Collisions Occur, which Causes the Temperature to Increase.
-Main Sequence Star: Once the Protostar becomes Hot enough, Nuclear Fusion Reaction Occur within the Core.
The Hydrogen Nuclei partake in Nuclear Fusion Reactions to Form Helium Nuclei.
Each Nuclear Fusion Reaction Releases Heat & Light Energy, which keeps the Core Hot.
-Red Supergiant: Eventually, the Main Sequence Star will Run Out of Hydrogen Gas in its Core.
Once this Happens, the Nuclear Fusion Reaction in the Core will Start to Die Down.
Hence, the Core Shrinks & Heats Up.
The Core will Shrink, b.c. now the Inward Force of Gravity > Outward Force of Pressure. BC the Outward Force of Pressure came from the Expanding Heat from the Nuclear Fusion Reactions in the Core.
Soon, a new Series of Nuclear Fusion Reactions Occur around the Core, with the Helium Nuclei, which Fuse to form Beryllium Nuclei.
These Nuclear Fusion Reactions will Cause the Outermost Part of the Star top Expand, & it will Become a Red Supergiant.
A Red Supergiant is Much Larger than a Red Giant.
-Supernova: Once the Nuclear Fusion Reaction Involving Helium Nuclei Stop, the Core of the Star will Suddenly Collapse, Causing a Gigantic Explosion.
This is Called a Supernova.
At the Centre of this Explosion, a Dense Body, known as a Neutron Star, will Form.
The Outermost Remnants of the Star (the Red Dust Layer) will be Ejected into Space During the Supernova Explosion, Forming a Planetary Nebula.
-Neutron Star (or Black Hole): In the Case of the Biggest Stars, the Neutron Star that Forms at the Centre will Continue to Collapse under the Inwards Force of Gravity from its own Core, until it Forms a Black Hole.
A Black Hole is an Extremely Dense Point in Space that not Even Light can Escape from.
What is a ‘Black Hole’?
A Black Hole is an Extremely Dense Point in Space, that not even Light can Escape from.
What is a ‘Supernova’?
A Supernova is a Bright & Powerful Explosion that Happens at the End of a Large Star’s Life. (Only Occurs in Stars Larger than the Sun).
A Supernova Explosion Releases a Large Amount of…
Energy.
What is Released During a Supernova Explosion? (3)
-A Large Amount of Energy.
-All of the Elements which were Produced by the Nuclear Fusion Reactions.
-Neutrons.
What Happens with the Elements & Neutrons that are Released During Supernova Explosions?
The Elements & Neutrons Combine to Form Elements Heavier than Iron.
These then go on to Form New Planets & Stars.
Since the Earth Contains many Heavy Elements up to Iron, this is Proof that it must have Once been Made from the Remains of a Supernova.
