star sequence (life cycle)

39
Star Sequence (Life Cycle) Born in Stellar Nebula Stars are large balls of hot gas. They look small because they are a long way away, but in fact many are bigger and brighter than the Sun. Stars are made (or “born”) in giant clouds of dust and gas.

Upload: madeline-willis

Post on 01-Jan-2016

31 views

Category:

Documents


2 download

DESCRIPTION

Star Sequence (Life Cycle). Born in Stellar Nebula Stars are large balls of hot gas. They look small because they are a long way away, but in fact many are bigger and brighter than the Sun. Stars are made (or “born”) in giant clouds of dust and gas. - PowerPoint PPT Presentation

TRANSCRIPT

Page 1: Star Sequence (Life Cycle)

Star Sequence (Life Cycle)

Born in Stellar Nebula Stars are large balls of hot gas. They look small because they are a long way

away, but in fact many are bigger and brighter than the Sun.

Stars are made (or “born”) in giant clouds of dust and gas.

Page 2: Star Sequence (Life Cycle)

Sometimes part of the cloud shrinks because of gravity.

As it shrinks it becomes hotter and when it is hot enough, nuclear reactions can start in the centre…..

… and A Star is Born!

Page 3: Star Sequence (Life Cycle)

Once nuclear fusion is producing heat in the centre of the new star, this heats stops the rest of the star collapsing.

The star then stays almost exactly the same for a long time (about 10 billion years for a star like the Sun).

The balance between gravity trying to make the star shrink and heat holding it up is called Thermodynamic Equilibrium.

Page 4: Star Sequence (Life Cycle)

Depending on the star’s mass it becomes one of three general types of stars

Brown Dwarf – never fully develops into a star – not enough mass (hydrogen for fusion to continue)

Average Star (Our Sun) MASSIVE Star

Page 5: Star Sequence (Life Cycle)

Average Stars

Also known as Main Sequence stars – make up 90% of stars in space

Become Red Giants as hydrogen resources are depleted

Then can break up into a Planetary Nebula Remaining part of the star becomes a White

Dwarf as it cools Once all heat is gone it then becomes a Black

Dwarf and dies.

Page 6: Star Sequence (Life Cycle)

Massive Stars

Become Super Red Giants as hydrogen resources are depleted

Then explodes into a Super Nova Remaining part of the star becomes either a Neutron Star, or a Black Hole and dies.

Page 7: Star Sequence (Life Cycle)

The life of a star During its “life” a star will not change very

much. However, different stars are different colour,

size and brightness. The bigger a star, the hotter and brighter it is.

Hot stars are Blue. Smaller stars are less bright, cooler and Red.

Because they are so hot, the bigger stars actually have shorter lives than the small, cool ones.

Page 8: Star Sequence (Life Cycle)

How does a star “die”? Eventually, the hydrogen (the “fuel” for the

nuclear fusion) in the centre of the star will run out

• No new heat is made and gravity will take over and the center of the star will shrink.

• This makes the very outside of the star “float up” and cool down, making the star look much bigger and redder - a Red Giant star.

Page 9: Star Sequence (Life Cycle)

The second Red Giant stage As the centre collapses, it becomes very hot

again, eventually getting hot enough to start a new kind of nuclear fusion with Helium as the fuel.

Then the Red Giant shrinks and the star looks “normal” again.

This does not last very long, though, as the Helium runs out very quickly and again the star forms a Red Giant.

Page 10: Star Sequence (Life Cycle)

The end of a Sun-like star

For a star like the Sun, no more nuclear fusion can take place, so the centre of the star will then keep collapsing.

• Eventually it can become almost as small as the Earth, but with the same mass as a whole star! This very dense object is called a White Dwarf.

• A piece of White Dwarf the size of a mobile phone would weigh as much as an elephant on the Earth!

Page 11: Star Sequence (Life Cycle)

Hetrzsprung- Russell (H-R) DiagramIllustrates important things about starsBrightness Absolute Magnitude

usually shown on right-hand Y-axis

Luminosity usually shown on left-hand Y-axis

Temperature/Color Spectral Class

shown on X-axis

Page 12: Star Sequence (Life Cycle)
Page 13: Star Sequence (Life Cycle)
Page 14: Star Sequence (Life Cycle)
Page 15: Star Sequence (Life Cycle)

Nebulae

Emission NebulaeEmission nebulae are clouds of high temperature gas. The atoms in the cloud are energized by ultraviolet light from a nearby star and emit radiation as they fall back into lower energy states (in much the same way as a neon light). These nebulae are usually red because the predominant emission line of hydrogen happens to be red (other colors are produced by other atoms, but hydrogen is by far the most abundant). Emission nebulae are usually the sites of recent and ongoing star formation. (M 42 shown)

Page 16: Star Sequence (Life Cycle)

M 42 The Orion Nebula

Page 17: Star Sequence (Life Cycle)
Page 18: Star Sequence (Life Cycle)

Reflection nebulae are clouds of dust which are simply reflecting the light of a nearby star or stars. Reflection nebulae are also usually sites of star formation. They are usually blue because the scattering is more efficient for blue light. Reflection nebulae and emission nebulae are often seen together and are sometimes both referred to as diffuse nebulae. (NGC 7023 shown)

Reflection Nebulae

Page 19: Star Sequence (Life Cycle)
Page 20: Star Sequence (Life Cycle)

Dark nebulae are clouds of dust which are simply blocking the light from whatever is behind. They are physically very similar to reflection nebulae; they look different only because of the geometry of the light source, the cloud and the Earth. Dark nebulae are also often seen in conjunction with reflection and emission nebulae. A typical diffuse nebula is a few hundred light-years across. (NGC 2264 shown; see also the Horsehead Nebula)

Dark Nebulae

Page 21: Star Sequence (Life Cycle)

NGC 2264

Page 22: Star Sequence (Life Cycle)

Horsehead Nebula

Page 23: Star Sequence (Life Cycle)

Planetary nebulae are shells of gas thrown out by some stars near the end of their lives. Our Sun will probably produce a planetary nebula in about 5 billion years. They have nothing at all to do with planets; the terminology was invented because they often look a little like planets in small telescopes. A typical planetary nebula is less than one light-year across. (M 57 shown)

Planetary Nebulae

Page 24: Star Sequence (Life Cycle)

M 57 Ring Nebula

Page 25: Star Sequence (Life Cycle)

Supernovae occur when a massive star ends its life in an amazing blaze of glory. For a few days a supernova emits as much energy as a whole galaxy. When it's all over, a large fraction of the star is blown into space as a supernova remnant. A typical supernova remnant is at most few light-years across. (M 1 shown)

Supernovae

Page 26: Star Sequence (Life Cycle)

M 1 Supernova Remnant

Page 27: Star Sequence (Life Cycle)
Page 28: Star Sequence (Life Cycle)

M 1 Supernova was discovered in 1054 and was visible for 23 days during the daytime, and easily seen for 2 years at night. It apparently was depicted in “cave paintings”

Page 29: Star Sequence (Life Cycle)

Trifid Nebula

Page 30: Star Sequence (Life Cycle)

Lagoon Nebula

Page 31: Star Sequence (Life Cycle)

Eta Carinae

Page 32: Star Sequence (Life Cycle)

NGC 2440

Page 33: Star Sequence (Life Cycle)

Helix Nebula

Page 34: Star Sequence (Life Cycle)

Dumbbell Nebula

Page 35: Star Sequence (Life Cycle)

Cats Eye Nebula

Page 36: Star Sequence (Life Cycle)
Page 37: Star Sequence (Life Cycle)

Vela Supernova Remnant

Page 38: Star Sequence (Life Cycle)

Veil Nebula

Page 39: Star Sequence (Life Cycle)

1987A Supernova