Search results
Results from the WOW.Com Content Network
A protostar is a very young star that is still gathering mass from its parent molecular cloud. It is the earliest phase in the process of stellar evolution . [ 1 ] For a low-mass star (i.e. that of the Sun or lower), it lasts about 500,000 years. [ 2 ]
After the density of infalling material has reached about 10 −8 g / cm 3, that material is sufficiently transparent to allow energy radiated by the protostar to escape. The combination of convection within the protostar and radiation from its exterior allow the star to contract further. [30]
The energy source of PMS objects is gravitational contraction, as opposed to hydrogen burning in main-sequence stars. In the Hertzsprung–Russell diagram , pre-main-sequence stars with more than 0.5 M ☉ first move vertically downward along Hayashi tracks , then leftward and horizontally along Henyey tracks , until they finally halt at the ...
A star forms by accumulation of material that falls in to a protostar from a circumstellar disk or envelope. Material in the disk is cooler than the surface of the protostar, so it radiates at longer wavelengths of light producing excess infrared emission. As material in the disk is depleted, the infrared excess decreases.
The collapse releases gravitational energy, which heats up the protostar. This process occurs on the free fall timescale, which is roughly 100,000 years for solar-mass protostars, and ends when the protostar reaches approximately 4000 K. This is known as the Hayashi boundary, and at this point, the protostar is on the Hayashi track.
Since about half of all known stars form systems of multiple stars and because Jupiter is made of the same elements as the Sun (hydrogen and helium), it has been suggested that the Solar System might have been early in its formation a protostar system with Jupiter being the second but failed protostar, but Jupiter has far too little mass to ...
The difference in energy production of this cycle, compared to the proton–proton chain reaction, is accounted for by the energy lost through neutrino emission. [22] CNO cycle is highly sensitive to temperature, with rates proportional to T^{16-20}, a 10% rise of temperature would produce a 350% rise in energy production.
For energy transport refer to Radiative transfer.. The different transport mechanisms of high-mass, intermediate-mass and low-mass stars. Different layers of the stars transport heat up and outwards in different ways, primarily convection and radiative transfer, but thermal conduction is important in white dwarfs.