Stellar Evolution
No description yet. This curated deck is ready for daily study.
Card preview (24)
What is ISM?
Interstellar Medium - gas and dust between stars.
Differentiate between ISM dust and gas and effect on light.
ISM gas does not significantly block light but it does scatter it. ISM dust blocks it
What is a nebula?
An interstellar cloud.
What is dark nebula?
Made up of dust grains blocking any visible light coming from stars that lie behind it.
What is reflection nebula?
Haze around stars caused by fine grains of dust in a lower concentration than in dark nebula. Light from star is scattered but not blocked.
Why do reflection nebula have blue color?
Scatter blue light more efficiently than red.
What type of nebula appears red in colour?
Emission nebula
What is Interstellar reddening and extinction?
Extinction is the reduction in the intensity of light. Reddening is scattering of bluer component.
What must happen for a star to form?
Interstellar material needs to condense to form a star so the force of gravity must overwhelm the internal pressure pushing the material apart.
What are Barnard objects? Give another name.
Extremely dense areas compared to ISM. Are dark nebulae where most star formations happen. Bok Globules.
T or F. A dark nebula is dark at all wavelengths.
False.
T or F. A protostar shrinks to enter main sequence, due to thermal emission being the main energy source.
True.
Distinguish between layers of different stars depending on size.
Less than 0.4 M Consists of core, convective. 0.4 M to 4 M Consists of core, radiative and convective. More than 4M Consists of core, convective and radiative.
What is a brown dwarf? What is the mass limited?
Failed star never reaches main sequence, can’t do fusion. 0.08 solar masses.
What is the upper limit for the mass of a successfully formed star?
200 solar masses.
HII regions are prominently red and are associated with what type of star?
Blue giant stars.
Is it possible to distinguish between a source redshifted and a source reddened by dust?
Yes spectroscopically the effects are different although visually the same.
T or F. The greater the mass of the protostar the faster it gets to the main sequence?
True.
What is stellar evolution?
Stellar evolution is a delicate dance between internal pressure and inward force of gravity.
When does a protostar become a main sequence star?
When hydrogen fusion begins.
Relationship between time on main sequence and mass.
1 / M^2.5
What are red dwarfs?
Stars with masses between 0.8 M and 0.4 M.
Explain the steps when core collapses.
More internal pressure Outer layers expand More Luminosity and less surface temperature
Explain the steps when core expands.
Less internal pressure Outer Layers Contract Less luminosity and more surface temperature