Space Week 6 -The Universe Notes

Life and Death of Stars Stars are Huge spheres of hot gas that emit light and other forms of

electromagnetic radiation. The distance between stars is measured in light years (the distance that light

travels in one year) Stars produce energy by nuclear fusion, fusing hydrogen into helium

Layers of a Star The core (15,000,000 K- site of nuclear fusion) Radiative Zone (2,500,00 K) Convective Zone (1,000,000 K) Photosphere (6,000 K – layer that produces light) Chromosphere (4,000 – 50,000K- layer that produces color) Corona (2.000.000 K-layer that produces Ultraviolet rays )

Studying the Stars Stars are classified by brightness

Absolute magnitude is the brightness of a star at a distance of 10 parsecs

Apparent magnitude is the brightness of a star as seen from Earth Color of a star indicates temperature of a star

Hotter stars are blue in color Cooler stars are red in color

The spherical lines can indicate the composition of a star

Fate of Stars The Hertzsprung-Russell diagram is a graph of all the stars in the Milky Way

Galaxy The temperature is on the x-axis The luminosity or brightness is on the y-axis Our sun is a main sequence star (typical)

Birth of a Star Stars are formed from a cloud of gas or dust called a nebula The cloud condenses to form a protostar The protostar becomes a star when the core of the star reaches 15,000,000 K

and nuclear fusion begans

Star Life The more massive stars live for millions of years The less massive stars live for billions of years Throughout the lives of stars, elements are fused into larger elements

( hydrogen to helium to carbon to oxygen to iron )Life Cycle of Stars

Stars that are less massive go from a main sequence star to a red giant and finishes as a white dwarf

Stars that are more massive go from a giant star to a supernova

End of a Stars Life Stars that are less than 1.4 solar masses will use up all of its hydrogen and

helium and become a white dwarf Stars that are between 1.4 and 3.0 solar masses will produce a Type I

supernova, leaving a neutron star Stars that are greater than 3.0 solar masses produces a Type II supernova,

collapsing and producing a black hole

Galaxies A galaxy is a collection of millions or billions of stars Galaxies are grouped in clusters The Milky Way is a special galaxy (our galaxy) Types of Galaxies (by shape)

Spiral (blue stars) Elliptical (red stars) Irregular galaxies

Quasars Quasars are the most distant and the most radiant objects in the universe

(center of distant galaxies)

Origin of the Universe The universe is everything in space The Big Bang states that the universe began with a giant explosion 10 – 20

billion years ago Proof of the theory is the red shift of stars showing the universe is expanding

Future of the Universe The universe will keep expanding forever The expansion of the universe will gradually slow down and the universe will

approach a limit in size the universe will stop expanding and start to fall back in on itself

Tools to Study the Universe Reflecting telescopes use mirrors to magnify the image Refracting telescopes use lenses to magnify the image Radio telescopes collect radio waves to study the stars Spectroscopes analyze the light given off by stars to indicate composition,

movement, and temperature of stars

What is the correct order of telescope advancement? Refracting , reflecting, radio

Why do astronomers measure interstellar distance in light years instead of Kilometers?

Miles and kilometers are to small of a unit

What is the correct age progression of a star? Nebula, main sequence, red giant, white dwarf

What is the next likely stage of a protostar? Main sequence

Spiral galaxy

Elliptical galaxy

Irregular galaxy