The Universe

Electromagnetic Radiation Light that travels directly through space in the form of waves – electromagnetic radiation.

Tools of Modern Astronomy Astronomers today use tools that help them to study the universe. Telescopes – collect and focus different types of electromagnetic radiation, including visible light. Types: Visible light telescope Radio telescope

Tools of Modern Astronomy Satellites – telescopes that orbit the Earth, outside Earth’s atmosphere, and can detect x-rays, UV rays and gamma rays that would otherwise be blocked. Hubble Space Telescope The Hubble Space Telescope: 5:04min

Orion Nebula

Crab Nebula

Galaxy M74

Young Star Forming

Centaurus A

The Universe The Sun, Planets and Moons make up our Solar System. Our solar system is one of many that make up our Galaxy, The Milky Way. The Milky Way is one of many galaxies that make up the Universe. Because the universe is so expansive we measure the distance from one object to the next in light years.

Light Years The distance that light travels, through space, in one year = light year. 300,000 km/sec or 9.5 million million km Our closest star, Proxima Centauri, is 4.2 light years away. It takes the light from Proxima Centauri 4.2 years to reach Earth

Classifying Stars A star is a huge sphere of glowing gas. Consist of mostly hydrogen (H) and Helium (He) Make energy by nuclear fusion The sun is an average-brightness star Astronomers classify stars according to their physical characteristics: Size Temperature Brightness

Star Size Star Temperature Stars range in size: Neutron star – smallest, about 20km in diameter White Dwarf Star ½ the size of Earth Medium-sized Star Our Sun Giant Star Supergiant Star Betelgeuse If it took the place of our sun it would extend past Jupiter. A star’s color reveals its temperature. Cool stars Reddish (3000°C) to Red-orange (4,500°C) Warmer stars Orange (5,000°C) to white (10,000°C) Hot stars Blue-white (20,000°C) to Blue (50,000°C)

Temperature: Color: Red (Cool) Yellow (Warm) White (Hot)

Star Brightness The brightness of a star depends on its size and temperature. How bright a star looks from Earth - Apparent Magnitude. The closer the star the brighter it is How bright the stars would be if they were all at a standard distance from Earth – absolute magnitude.

Hertzsprung-Russell Diagram The two most important characteristics of stars are the temperature and the absolute magnitude. Plotted against each other you get the H-R Diagram 90% of all stars are main-sequence stars Giants and supergiants are bright but low temperature White dwarfs are hot but not very bright

H-R Diagram Brightness Increasing (°C)

Lifecycle of a Star Death Birth

Lifecycle of a Star Just like humans, stars have lifecycles. They’re born, grow, become middle aged and then die. Birth = Nebula Lots of gas over a large volume Gravity pulls some of the gas and dust into a Protostar Proto in Greek = “earliest” When nuclear fusion begins a star is born! How long a star lives depends on its mass Smaller stars live longer (200 billion years) Burn through their fuel slower Medium stars (10 billion years) Large stars (10 million years).

Death of a Star Middle Aged = when a star begins to run out of fuel, the center shrinks and the outer parts expand becoming a red giant or supergiant. Death - Once the fuel runs out completely it becomes a white dwarf, neutron star or black hole. White Dwarfs – small to medium mass stars, 10+ billion years old. About ½ the size of Earth with as much mass as the sun. When a white dwarf stops glowing, from left over energy, it becomes a black dwarf.

Death of a Star Neutron Star – a dying giant or supergiant that suddenly explodes, supernova. Material left over from an exploding supernova becomes a neutron star. Smaller and denser than white dwarfs. 3. Black Holes – the most massive star. Contain more than 40 times the mass of the sun. After exploding to become a supernova the gravitational pull is so large that it pulls the gases inward to the point nothing can escape, not even light.

Galaxies Our solar system belongs to the Milky Way galaxy. There are billions of galaxies in the universe. 3 main categories: Spiral galaxies The Milky Way Elliptical galaxies Irregular galaxies

Galaxy Categories Irregular Galaxy Spiral Galaxy (Milky Way) Elliptical Galaxy

Big Bang Theory Roughly 10-15 billion years ago the universe formed as an enormous explosion. Its been expanding ever since and is a billion times larger than it was at the beginning.