1 / 14

ASTRONOMY

ASTRONOMY. Chapter 28 The Aging and Death of Stars Like the Sun. Low-mass Stars. Low-mass stars are stars with masses less than about 8 M˳. This includes the vast majority of stars. End of Main Sequence Life.

louisa
Download Presentation

ASTRONOMY

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. ASTRONOMY Chapter 28 The Aging and Death of Stars Like the Sun

  2. Low-mass Stars • Low-mass stars are stars with masses less than about 8 M˳. • This includes the vast majority of stars.

  3. End of Main Sequence Life • During its 10 billion years on the main sequence, our sun will fuse all of the hydrogen in it’s core. • During this time, the star is in hydrostatic equilibrium. • The core now contains only helium. • Hydrogen is still fusing in a shell surrounding the core.

  4. End of Main Sequence Life • No Fusion inside the core means: • Hydrostatic equilibrium is lost • Core contracts gravitationally • Core gets hotter • Shell of fusing hydrogen gets hotter causing the rate of fusion to increase • Outer layers of the star are heated and expand outward • Surface temperature decreases due to increased surface area

  5. Red Giants http://25.media.tumblr.com/tumblr_l5pd17Hys51qa0fruo1_400.jpg

  6. Red Giants • Our sun will swell to nearly the size of the Earth’s orbit. • The core continues to contract and heat up. • When the core reaches 108 K which starts the triple alpha reaction. • For stars like our sun this happens rapidly and is called a helium flash. • He fuses in the core forming carbon and oxygen.

  7. Planetary Nebulae • When the C core forms, it contracts and heats up just like the He core • H and He fusing shells form and are unstable • The star begins to pulsate, losing some mass with each pulsation • These gas envelopes move out and become transparent • A planetary nebula is formed.

  8. Planetary Nebulae

  9. Planetary Nebulae

  10. Planetary Nebulae

  11. Planetary Nebulae

  12. White Dwarfs • Red Giant stars are not massive enough to fuse C • Stars with Masses up to 8 M˳ lose much of their mass and are now at or below 1.4 M˳ • They shrink and become stable and very hot and are called white dwarfs. • They are very faint, being below and to the left of the main sequence.

  13. Black Dwarfs • The white dwarf radiates energy for billions of years • There is no source of new energy • It cools and eventually becomes a black dwarf. • We do not think that any white dwarf has reached this stage yet.

  14. Novae • Some white dwarfs in binary systems will collect gas from the other star. • When enough has accumulated, the white dwarf will again begin fusing the H • It becomes much brighter in a matter of days, then gradually dimming • These newly visible stars are called novae

More Related