Timeline for Energy and colours of the stars
Current License: CC BY-SA 3.0
13 events
| when toggle format | what | by | license | comment | |
|---|---|---|---|---|---|
| Mar 28, 2017 at 19:28 | comment | added | Curio | Sorry, before I said a stupid thing. When a star stays in the costant phase, it should be costant in size. It doesn't increase nor decrease its volume. However, returning to the previous speech, I discovered why the blue dwarfs have a lot of energy and they are very small (degenerate matter). Before I thought that they are ALWAYS ideal gases, but I was wrong | |
| Mar 28, 2017 at 15:51 | comment | added | Bill N | The primary fusion process changes to helium, carbon, etc and they produce higher power which creates the larger pressure which makes the star swell which makes the diameter and surface area larger. When the processes finish, the star collapses and explodes, leaving a hot, dead core which can form a white dwarf, neutron star, or black hole. All this is explained in much more detail in an astrophysics book like Ryden and Peterson, Foundations of Astrophysics. | |
| Mar 28, 2017 at 11:30 | comment | added | Curio | But with the time the fuel finishes and the energy should be less | |
| Mar 28, 2017 at 2:16 | comment | added | Bill N | @Curio This isn't the place to answer all those questions. There are many books and websites which present stellar development in a coherent, orderly way which will answer all these questions. REgarding the question about decreasing temperature, no that's not right. The cool surface is due to the inflation and the increased surface area. | |
| Mar 27, 2017 at 20:26 | comment | added | Curio | @BillN so temperature of stars decreases hand to hand the fuel burns. Is it right? Furthermore, how can red giants be so big? At the end of the life of a star, the core compress itself, so the temperature increases , so the pressure increases and the star should inflate itself and increase its volume. So red giants needs a lot of energy. But for example a blue dwarf has got a lot of energy but it is very small...why? | |
| Mar 27, 2017 at 19:35 | comment | added | Curio | @RobJeffries what do you mean for "opaque envelopes"? How do the red giants burn the shell? | |
| Mar 27, 2017 at 17:16 | comment | added | Bill N | @Curio Re-read what I said. I didn't say "They are not blue." I eliminated elemental makeup as a primary reason for their being blue. Probably a semantic/grammatical misunderstanding. Young stars with lots of mass will have larger core power causing the surface to be very hot. Old stars with moderate to large mass will be expanded and shell-burning hydrogen and core fusing helium or carbon, but the intensity (power/area) reaching the surface (because they are very large) won't be as great as the large young stars, so the red giant surfaces will be cooler, hence appearing redder (Stefan's Law) | |
| Mar 27, 2017 at 16:23 | comment | added | ProfRob | @Curio More metal-rich stars have more opaque envelopes. This makes them larger for the same internal energy production, which means their surface temperatures are lower at the same mass. Your other query for Bill N is answered simply as blue main sequence stars are more massive than red main sequence stars. Red giants can be more massive than blue main sequence stars, but they are also larger and generating their energy in a different way (shell burning rather than core burning). | |
| Mar 27, 2017 at 16:07 | comment | added | Curio | @Rob Jeffries why this? Do metal-rich main sequence stars absorb more energy? | |
| Mar 27, 2017 at 16:04 | comment | added | Curio | Two things. First you talked about blue stars and immediately you said "They are not blue". I'm confused. Furthermore at the third paragraph you said that blue stars have more mass than red stars, but for example the red giants? They have a lot of mass but they are red | |
| Mar 27, 2017 at 12:31 | comment | added | Bill N | @RobJeffries I agree. Considering the level of the question and the ideas proposed in it, I decided not to delve into the deeper reasons for temperature differences. Thanks for your comment. | |
| Mar 26, 2017 at 22:56 | comment | added | ProfRob | This answer is ok to first order, but the composition of a star does affect its temperature and colour. Metal-poor main sequence stars are hotter and bluer than metal-rich main sequence stars of the same mass. Also, the colours of cool L and T dwarfs are directly influenced/caused by molecular absorption. | |
| Mar 26, 2017 at 21:22 | history | answered | Bill N | CC BY-SA 3.0 |