Structure of the Universe What does our universe

Structure of the Universe What does our universe look like?

Galaxies • Galaxy- collection of billions of stars and various amounts of gas and dust held together by gravity – Average galaxy has 100 billion stars

Galaxy • Galaxies have been classified on shape – Elliptical – Irregular – Spiral

Galaxy • Milky Way Galaxy- our solar system is part of this spiral shaped galaxy – 200 billion stars

Galaxy

Stars • Star- large ball of gas held together by gravity that produces tremendous amounts of energy and shines – Make up the majority of known matter in a galaxy

Stars • Energy Production: – Nuclear Fusion- the combining of nuclei of smaller elements to form the nuclei of larger elements – The Sun converts hydrogen nuclei into helium nuclei

Stars • Luminosity and Temperature: – Luminosity- a measure on how bright a star is compared to our Sun – Luminosity and temperature are used in classifying the different types of stars

Stars

Star Types • Our Sun (medium sized star) is 109 times bigger then Earth • Most stars are bigger the Earth

Star Types • Main Sequence Stars: – 90 % of stars studied and located on the Luminosity and Temperature of Stars Diagram fall on a broad band grouped together – Most Stars spend their life here – These are your average size, temperature, and luminosity

Star Types • Giant Stars: – Red, orange, and yellow giant stars – Commonly seen because of their size – Low-temperature stars in late stages of their evolution

Star Types • Super Giants: – 100 to 1000 times the size of our Sun – Highly luminous – Late stage development and usually explode in an event called a supernova – Blue super giants are the brightest and exhibit the highest temperature

Star Types • White Dwarfs: – Around the size of the Earth – Hot on the surface – Low in luminosity

Star Types • Black Dwarfs: – After a white dwarf cools and no longer emits electromagnetic energy it is a “dead star” or black dwarf – Common in the universe because many have used up their supply of hydrogen and can no longer main nuclear fusion

Star Types

Star Origin and Evolution • Stars have an evolution--- origin, life, and ending – Originate from clouds of dust and gas – Gravity causes them to clump up forming larger balls of dust and gas – When gravitational contraction creates enough heat they start nuclear fusion

Star Origin and Evolution • Stars spend most of their lives as a main sequence star – Massive stars then can undergo a supernova and create a black hole (extremely high mass) or a neutron star – Lower mass stars become a white dwarf and burn out into a black dwarf