1 / 17

Star Types & Lifecycle

Star Types & Lifecycle. Consider these questions:. Is our Sun an average star or a unique star? Will the Sun and Earth go on forever?. Our Sun. Our Sun is an average medium sized star. It has a lifespan of 10 billion years It is about half way through its lifespan

moral
Download Presentation

Star Types & Lifecycle

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. Star Types & Lifecycle

  2. Consider these questions: • Is our Sun an average star or a unique star? • Will the Sun and Earth go on forever?

  3. Our Sun • Our Sun is an average medium sized star. • It has a lifespan of 10 billion years • It is about half way through its lifespan • Mercury, Venus, and Earth will be destroyed when the Sun becomes a “Red Giant” (in about 4 billion years) • All stars go through different stages • Small stars live very long quiet lives • Large stars live very short violent lives

  4. Observed Properties of Stars • When we look into the sky, what properties of stars can we observe? • Brightness (Luminosity) • Stars in the sky have different brightness (called Magnitude) • Some brightness differences are the result of distance • But, even stars at the same distance have different brightness • Colour (Temperature) • Starlight can be split into a rainbow called a spectra. • Spectra tell us that stars have different temperatures and compositions. • E.g. Blue objects are hotter than red objects • Note: Stars are too distant to see their disks or surface features.

  5. The Hertzsprung-Russell Diagram • Scientists love to plot data on graphs! • In the early 1900’s astronomers measured the luminosity and colour of 1000’s of stars. • When they plotted this data they found interesting relationships!

  6. Life Cycle of Stars • They identified definite groupings (types) of stars: • Red Dwarfs • White Dwarfs • Red Giants • Blue Giants • Supernovas • Neutron Stars • Black Holes • Further research revealed that these types of stars are just different stages in the life cycle of stars. • Stars spend most of their life on the “main sequence” in the middle of the H-R Diagram

  7. Activity – Part 1 • Complete the HR-Diagram in your handout based on the following notes and discussion.

  8. 1. Protostars – New Stars • Properties: • Luminosity: Medium • Temperature: Cool • After a few million years the hydrogen gas and dust from the cloud has compressed enough to form stars. • Stars get their energy by converting hydrogen into helium and other elements. • This process is called nuclear fusion • It is the same principle as a hydrogen bomb • The Pleiades Cluster contains many stars that are close together. • After 1 million years these stars will have spread throughout the galaxy • Our Sun began this way

  9. 2. Main Sequence – Adult Life • Properties - High Mass Stars • Luminosity: High • Temperature: Hot • Properties - Low Mass Stars • Luminosity: Medium • Temperature: Medium • Stars spend most of their life on the Main Sequence. • High mass stars live only a few million years (They burn through their hydrogen very fast) • Low mass stars live billions of years (They burn through their hydrogen very slowly) • Our Sun is a medium mass yellow star

  10. 3. Brown Dwarfs • Properties: • Luminosity: Very Dim • Temperature: Cool • Small stars do not have enough gravity to create the conditions necessary to burn helium once their hydrogen is used up. • Small stars just fade away after 100 billion years. • The universe it too young to have any dead brown dwarfs yet. • Jupiter could have become a brown dwarf if it was just a few times bigger. • Most stars in the sky occur in pairs called binary stars.

  11. 4a. Red Giants – Old Age • Properties – Low and Medium Mass Stars • Luminosity: Bright • Temperature: Cool • When a star runs out of hydrogen fuel… • It starts to burn helium • This causes the star to greatly expand • Our Sun will become a Red Giant in about 5 billion years • It will expand to near the orbit of Mars • Earth will be burnt to a crisp

  12. 4b. Supergiant – Old Age • Properties – High Mass Stars • Luminosity: Very Bright • Temperature: Very Cool • When a star runs out of hydrogen fuel… • It starts to burn helium • This causes the star to greatly expand • Massive Blue stars become Supergiants • They expand to bigger than the orbit of Jupiter! • They are extremely unstable!

  13. 5. White Dwarfs – End of Life • Properties: • Luminosity: Low • Temperature: Very Hot • Medium size stars end their life as a White Dwarf • This is what is left behind at the center of a Planetary Nebula • They the remains of the core of the original star • A white dwarf is extremely dense and hot • The Sun will end up as a White Dwarf Earth and White Dwarfare about the same size.

  14. 5b. Planetary Nebula • Planetary nebulas are the cloud of dust and gassurrounding a white dwarf • After a few million years the red giant star will have used up all its helium. • What is left is Lithium and Carbon • These stars do not have enough gravity to create the conditions necessary to burn heavier elements • They puff their outer layers out like a “smoke ring” • These “smoke rings” are called Planetary Nebula • Planetary Nebula have nothing to do with planets • Also, They have nothing to do with Hydrogen Nebula • Our Sun will create a Planetary Nebula when it dies

  15. 6. Neutron Stars & Black Holes • Properties: • Luminosity: Very Low • Temperature: Hot • These are created at the end of life of massive stars. • They are what is left after a supernova. • Neutron Star – A star made of solid neutrons • There is a neutron star at the center of the Crab Nebula • Black Hole – Extreme gravity, A “hole” in space • Nothing can escape (not even light) • There is a black hole at the center of our galaxy

  16. 6b. Supernova - Death Same star • A massive explosion related to the death of high mass stars. • Occurs when the star has used up all of its fuel for nuclear fusion. • Gravitational collapse generates tremendous instantaneous energy and temperature increase. • Results in a temporary extreme brightening of the star. • Brightening lasts days or a few weeks. • After 100’s or 1000’s of years it results in a Supernova Nebula Cloud. • The Crab Nebula was observed a supernova star in 1054.

  17. Activity – Part 2 • Complete the Stellar Lifecycle chart in your handout based on your notes and pages 341 to 349 of the textbook.

More Related