Molecular Clouds
Stage Duration: Approx. 10 million years
Molecular clouds are cold concentrations of interstellar gas and dust. These clouds contain CO (carbon monoxide) and H2 (2 parts hydrogen) which have atoms that bind together, meaning they are molecular.
Molecular clouds can exist for millions of years without forming stars however, the density -caused by the extreme cold (10 to 20K), clumps the gases together- encourages them to form. This means that the core sections of the clouds that are the most dense collapse under their own weight, beginning to form into ‘clumps’ which then form into protostars.
Stage Duration: Approx. 10 million years
Molecular clouds are cold concentrations of interstellar gas and dust. These clouds contain CO (carbon monoxide) and H2 (2 parts hydrogen) which have atoms that bind together, meaning they are molecular.
Molecular clouds can exist for millions of years without forming stars however, the density -caused by the extreme cold (10 to 20K), clumps the gases together- encourages them to form. This means that the core sections of the clouds that are the most dense collapse under their own weight, beginning to form into ‘clumps’ which then form into protostars.
‘Star Formation’ [online] N/A, Available: http://abyss.uoregon.edu/~js/ast122/lectures/lec13.html [Accessed 28/10/15]
Protostars
Process Duration: Approx. 3 million years+
Once the molecular cloud has formed into clumps they break out of the cloud core and are called a protostar has they develop their own gravity, turning into a rotating disk. This is due to the angular momentum that pushes the gas clump into a more spherical shape.
A centre is formed in the protostar and a planetary system is formed slowly, from a nebular disk. The size of the protostar is increased by a factor of 100 as matter moves towards the astronomical body from gravity. The protostar becomes stable when the pressure finally stops the infalling gas through a release of energy through heat (stellar wind) which causes the atomic nuclei to form together
‘Star Formation’ [online] N/A, Available: http://abyss.uoregon.edu/~js/ast122/lectures/lec13.html [Accessed 28/10/15]
T-Tauri Stars
Duration: As long as hydrogen supplies last
Usually characterised by a ‘bipolar outflow’ of gases flowing from both poles of the star, this stage is the ’pre-main sequence of stars’. This is due to it still settling down before the main stage of the star’s life, as 50% of the mass is lost before this point.
Main signs of the T-Tauri stage include: heavy flow of particles from star (stellar winds), light areas that vary in regularity and activity (explosions, flares) on the surface that happen constantly. The stars at this stage are still within the clouds of gas they were originally born in as shown in the Orion Nebula with the collection of stars.
‘Star Formation’ [online] N/A, Available: http://abyss.uoregon.edu/~js/ast122/lectures/lec13.html [Accessed 28/10/15]
Red Dwarf
Once hydrogen supplies are used up in the core of the sun, a red giant is formed as there is not enough heat in comparison to the gravity, to support the core. It is named a red dwarf as there is still heat from hydrogen around the shell of the core. The star will eventually burn helium to carbon once it reaches a high enough density, collapsing under the pull of gravity. It will become a red super giant once the helium is exhausted from the star’s core, which will take approximately 100 million years.
Carbon will be embedded in expelled gas in a nebula once the sun loses its mass. A ‘planetary nebula’ will be created once the hot core converts into ions for the nebula, from the radiation.
A white dwarf will form once the core now predominantly carbon, cools.
Once hydrogen supplies are used up in the core of the sun, a red giant is formed as there is not enough heat in comparison to the gravity, to support the core. It is named a red dwarf as there is still heat from hydrogen around the shell of the core. The star will eventually burn helium to carbon once it reaches a high enough density, collapsing under the pull of gravity. It will become a red super giant once the helium is exhausted from the star’s core, which will take approximately 100 million years.
Carbon will be embedded in expelled gas in a nebula once the sun loses its mass. A ‘planetary nebula’ will be created once the hot core converts into ions for the nebula, from the radiation.
A white dwarf will form once the core now predominantly carbon, cools.
The Life Cycle of Stars [online recording] 2012, Institute of Physics, N/A.