1 / 15

Off the Main Sequence - The Evolution of a Sun-like Star Stages 7 - 9

Off the Main Sequence - The Evolution of a Sun-like Star Stages 7 - 9. Off the Main Sequence - The Evolution of a Sun-like Star Stages 7 - 9. These stages have already been discussed: Stage 1: Interstellar Cloud Stage 2: A Collapsing Cloud Fragment Stage 3: Fragmentation Ceases

tasmine
Download Presentation

Off the Main Sequence - The Evolution of a Sun-like Star Stages 7 - 9

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Off the Main Sequence - The Evolution of a Sun-like Star Stages 7 - 9

  2. Off the Main Sequence - The Evolution of a Sun-like Star Stages 7 - 9 These stages have already been discussed: Stage 1: Interstellar Cloud Stage 2: A Collapsing Cloud Fragment Stage 3: Fragmentation Ceases Stage 4: A Protostar Collapsing cloud has ripped apart atoms, temperature at around 1,000,000 K. Stage 5: Protostellar Evolution Central temperature around 5,000,000 K Protons still cannot overcome Coulomb repulsion Stage 6: A Newborn Star Core temperatures reach 10,000,000 K – Fusion begins

  3. Off the Main Sequence - The Evolution of a Sun-like Star Stages 7 - 9 These stages have already been discussed: Stage 7: The Main Sequence Core temperatures around 15,000,000 K Hydrostatic equilibrium (radiation pressure balances gravity) stable size and burning of hydrogen

  4. Off the Main Sequence - The Evolution of a Sun-like Star Stages 7 - 9 While on the main sequence, the star is burning hydrogen. It’s luminosity is determined by the stars mass. The most intense fusion is occurring at the center regions of the core (highest pressure and temperature). A star like the sun will remain on the Main Sequence for about 10 billion years

  5. Off the Main Sequence - The Evolution of a Sun-like Star Stages 7 - 9 Initial depletion of hydrogen occurs in the interior of the hydrogen burning core

  6. Off the Main Sequence - The Evolution of a Sun-like Star Stages 7 - 9 Helium cannot fuse because a temperature of around 108 K is required to overcome the coulomb repulsion to trigger fusion (helium has a charge of +2e). Once the hydrogen in the central core is depleted, hydrostatic equilibrium is lost and the central core begins to collapse as a result of strong gravity

  7. Off the Main Sequence - The Evolution of a Sun-like Star The Red Subgiant Branch Turn Off – the location on the H-R diagram where the star first leaves the main sequence as a result of hydrogen depletion in the core.

  8. Off the Main Sequence - The Evolution of a Sun-like Star The Red Subgiant Branch Heating of the gaseous envelope causes it to expand. Burning hydrogen in the expanding shell increases the luminosity Gravitational collapse of the core increases the temperature of the core. Hydrogen continues to burn outside of the central core.

  9. Off the Main Sequence - The Evolution of a Sun-like Star The Red Subgiant Branch Hydrogen Shell Burning – the fusion of hydrogen in shells of a star outside of the hydrogen depleted core. Because of the increase in pressure of the core due to gravitational collapse, the core temperatures will rise. The increase in thermal energy increases the temperature of the hydrogen burning (expanding) shell, which increases the amount of hydrogen fusion occurring in the shell. Therefore, the temperature goes up, along with a slight increase in luminosity. The star follows an almost horizontal path on the H-R Diagram.

  10. Off the Main Sequence - The Evolution of a Sun-like Star The Red Subgiant Branch Heating of the gaseous envelope causes it to expand. Burning hydrogen in the expanding shell increases the luminosity somewhat. Gravitational collapse of the core increases the temperature of the core. Increase in core temperature triggers more hydrogen fusion in the shell. Hydrogen continues to burn outside of the central core.

  11. Off the Main Sequence - The Evolution of a Sun-like Star The Red Subgiant Branch Red Subgiant Branch Gravitational collapse of the core increases the temperature of the core. Hydrogen continues to burn outside of the central core.

  12. Off the Main Sequence - The Evolution of a Sun-like Star The Red Subgiant Branch Red Subgiant Branch – the portion of the H-R Diagram that corresponds to the hydrogen shell burning portion of the life of a star related to the expansion of the radius and increase in luminosity of the star before helium burning is triggered in the core of the expanding star. There is a decrease in the surface temperature of the star as it expands.

  13. Off the Main Sequence - The Evolution of a Sun-like Star Stage 8 Stage 8 – the end of the Red Subgiant Branch. The temperature of the core is very high, triggering intense hydrogen fusion in the burning shell. The huge pressures in the burning shell beings to push the cooler outer shell outward, starting a great change in radius. R ≈ 3 Rsun Gravitational collapse of the core increases the temperature of the core. Hydrogen continues to burn outside of the central core.

  14. Off the Main Sequence - The Evolution of a Sun-like Star The Red Giant Branch Outer envelop cools. Hydrogen burning still occurs in the shells at a rapid rate producing very high luminosity. Internal pressures cause a big increase in radius.

  15. Off the Main Sequence - The Evolution of a Sun-like Star Stage 9 Core density ≈ 108 kg/m3 Core temp ≈ 108 K R ≈ 100 Rsun

More Related