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Astronomy Part 2

Astronomy Part 2. What do all those words mean?. Stars and Galaxies. The Evolution of a Star A nebula is a large cloud of gas (hydrogen) A star is born. Hydrogen gas clumps together because of gravity

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Astronomy Part 2

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  1. AstronomyPart 2 What do all those words mean?

  2. Stars and Galaxies • The Evolution of a Star • A nebula is a large cloud of gas (hydrogen) • A star is born. • Hydrogen gas clumps together because of gravity • As the hydrogen atoms move closer together temperature increase and the atoms start to fuse releasing even more energy. • The energy radiates into space as light and heat and a star is born.

  3. Stars • There are many different types of stars which vary in size and brightness (energy released). • Main sequence stars are average regular stars. • After the hydrogen fuel is exhausted the star expand and cools as it starts to fuse helium – this is a red giant. • After the helium is gone the star contracts further becoming a white dwarf.

  4. Still more stars • If the red giant is super massive (lots of mass – about 10 times that of our sun) then the changes are more rapid and violent. • The red giant is classified as a supergiant and instead of collapsing into a white dwarf it explodes into a supernova. • The core of an exploded supernova is called a neutron star as it is made of compacted neutrons of extremely high density. • If the core that remains is extremely large it can collapse into a black hole rather than a neutron star.

  5. Galaxies • There are many different types of galaxies (large groups of stars and dust held together by gravity). • Spiral galaxies – like our own galaxy (The Milky Way) • Elliptical galaxies – galaxies that form and ellipse • Irregular galaxies – older galaxies of no identifiable shape.

  6. The Milky Way Galaxy • The Milky Way Galaxy is our home galaxy and the sun orbits around in one of the arms of the spiral. • The Milky Way Galaxy contains approximately 1 trillion stars – a 1 followed by 12 zeroes. • 100,000 light years across • The sun orbits every 240 million years • Our latest estimates put the age of the universe at approximately 20-22 billion years old.

  7. Measuring intergalactic distances • When we get to galactic distances, even light years are not enough. Another unit that is used is the parsec. A parsec is approximately 3.16 light-years and is a metric unit enabling us to use kiloparsec, megaparsec, gigaparsec, etc. A parsec has to do with parallax which is a mathematical way of measuring distances involving geometry and angles. It stands for the parallax of one arc second.

  8. Telescopes • How do we know what is out there in space? • We use instruments that allow us to see far distances in space – telescopes. • There are many different types of telescopes. • Visible light telescopes • Radio telescopes • X-ray telescopes

  9. What is a telescope?

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