life cycle of a star
DESCRIPTION
The life and death of a star as needed to know by a 6th graderTRANSCRIPT
Science Daily StarterApril 27, 2008
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• Label page– Daily Starters April 28-May 2
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Science Daily StarterApril 27, 2008
• What is the first stage in the life cycle of a star?
Life Cycle of a Star
Ms. Hyche1st, 2nd, 6th period Science
Nebulae
• Nebulae– A nebulae is a cloud of gas and dust in outer
space.
– These clouds are often very large, spanning across many light years.
– There are many different kind of nebulas in the sky
Nebulaes
Ring Nebulae Double Lobed Nebulae
Life Cycle of Stars
• Just like people, stars are born, grow old, and eventually die.
• The difference is, stars exist for billions of years.
How do stars form?• They are born when clouds of gas
and dust come together and become very hot and dense. (nuclear fusion)
• As stars get older, they lose some of their material.
• Usually this is a gradual change, but sometimes it happens in a big explosion.
• Either way, when a star dies, much of its material returns to space.
• There some of it combines with more gas and dust to form new stars.
Types of Stars
• Determinded by size, mass, brightness, color, temperature, specturm, and age
• Main-sequence stars, giants, supergiants, white dwarfs
Main-Sequence Stars
• Second and longest stage
• Energy generated in the core, and released
• Size changes very little as long as there is a continuous supply of hydrogen atoms to fuse the helium atoms
Giants and Supergiants
• Third stage
• Star can become a red giant– A star that expands and
cools once it uses its hydrogen
– Star will shrink
Scale
White Dwarfs
• Final stage
• Size of the sun or smaller
• White Dwarf– Small, hot star that is the
leftover center of an older star
The Diagram That Did It!
• In 1911, a Danish astronomer named Ejnar Hertzsprung compared the temperature and brightness of stars on a graph.
• Two years later, American astronomer Henry Norris Russell made some similar graphs.
The Diagram That Did It
• Although they used different data, they had similar results.
• The combination of their ideas is now called the Hertzsprung-Russell, or H-R diagram.
– The H-R diagram is a graph showing the relationship between a star’s surface temperature and its absolute magnitude.
Continued
• The H-R-diagram has become a tool for studying the nature of stars.
• It shows how stars are classified by temperature and brightness AND it’s a good way to illustrate how stars change over time.
As stars age….
• Average stars (sun), become red giants and then white dwarfs
• More massive stars may explode with such intensity that they become strange objects such as supernovas, neutron stars, pulsars, and black holes
Supernovas
• Massive blue stars with short lives
• Supernova– Gigantic explosion in
which a massive star collapses.
Neutron Stars
• Neutron star– A star that has collapsed
under gravity to the point that the electrons and protons have smashed together to form neutrons
• Pulsar– Spinning neutron star
1987A
1987A
Blackholes
• Leftovers of a supernova that they collapse
• Black hole
– Object so massive and dense that even light can’t escape its gravity
Life Cycles
• The life cycle of a star varies, depending on the mass of the star.
• Higher mass stars develop more quickly than lower mass stars. Toward the end of their life, they also behave differently.
More on life cycles
• Stars form inside a cloud of gas and dust called a nebula.
• Gravity pulls gas and dust closer together in some regions of a nebula.
• As the matter contracts, it forms a hot, dense sphere.
• The sphere becomes a star if the center grows hot and dense enough for fusion to occur.
Death of a Star
• When a star begins to run out of fuel, its core shrinks and its outer portion expands.
• Depending on its mass the star becomes either a red giant or a supergiant.
• These evolve in very different ways.
Low or Medium Mass Star
• Low or medium mass star–Red Giant–Planetary Nebula–White Dwarf–Black Dwarf
High Mass Star
• High Mass Star–Supergiant–Supernova–Black hole (gravity so strong
that nothing, not even light, can escape) or neutron star
In conclusion….
1. Nebulae2. Main-Sequence Star3. Giants or Red Giants4. White Dwarfs5. Supernovas, Neutrons, Blackholes
