P7 Page 15 Flashcards
Describe in depth how clouds of dust and gas become a main sequence star.
1) stars star of as clouds of gas and dust(hydrogen+helium)
Gravity causes regions to clump up, when these clumps become dense enough, the clouds break up into a protostars.
2) Protostars continue to collapse under their own gravity,reducing in their volume. This increases the temperature and pressure. Eventually the centre of the protostar reaches a few million degrees, and hydrogen nuclei start to fuse together to form helium.
3) this releases enormous amounts of energy and creates enough outward pressure to stop gravitational collapse.
Describe the few stages in the formation of a main a sequence star.
1) clouds of dust and gas
2) Protostar
3) main sequence star
Describe the core of a star.
Most of the fusion in the star takes place in the centre. The pressure from the weight of the star makes the core hotter and denser than the rest of the star.
Describe the photosphere of a star.
The outer region of a star, form where energy is radiated into space. Energy released from fusion in the core is transported by photons of radiation and convection currents to the surface of the star. This part of the sun that we see form Earth.
What happens to a star when it runs out of hydrogen and helium nuclei to fuse?
I swells up to become a red giant or supergiant star. In the process of swelling up the photosphere cools.
What happens with fusion in a larger star?
The more massive a star is the hotter the core, the hotter the core, the heavier the nuclei it can fuse together- so it can create even heavier nuclei.
