Structure of the Universe

What makes up the Universe Sun Solar system Planets – orbits the Sun Moon Stars Composed of gas and emits light Formed in Nebulae Galaxy Large collection of stars, gas, and dust held together by gravity 3 shapes Groups of galaxies Super clusters Universe

Universe Distance Distances within the solar system are measured in astronomical units (AU) Astronomical units – the average distance between Earth and the Sun. Light year – the distance light travels in 1 year. Measure of distance NOT TIME Used to measure things beyond our solar system The farther away an object is, the longer it takes it’s light to reach Earth. # of AU’s in a light year = 10 trillion km

Measuring distance Light travels about 300,000 km/s Closest star to the sun and Earth is Proxima Centauri 4.3 years for light to travel to Earth. Light from the Sun takes about 8 min to reach Earth

Parallax The apparent change in an objects position caused by looking at it from two different points. EX: extend arm – stick up thumb- close 1 eye- notice thumb – open eye – close the other – thumb appears to “jump positions”.

Size of the observable universe Actual size not known Radiation from objects that formed in early universe have not reached Earth. Universe believed to have a radius of 14 billion years Universe is ever expanding outward Estimation 93 billion years

Structure of the universe Universe – space and all the matter and energy in it Galaxies dense Clusters and super clusters Nothing exists Voids New thinking: Universe is like a spider web Web = galaxies Space = voids

Classifying Galaxies Edwin Hubble 1st person to identify groups of stars as a galaxy. 3 type of galaxies Spiral Elliptical Irregular a massive galaxy cluster found to be 160 trillion times the mass of the Sun. The detail in this mass map was made possible thanks to the unprecedented depth of data provided by new Hubble observations, and the cosmic phenomenon known as strong gravitational lensing.

Types of Galaxies Spiral Elliptical Irregular Flat disks with spiral arms and bulges in their center core Look like a pin wheel or a hurricane Most common type Example: Milky Way Elliptical Rounded, like a football or egg Irregular Galaxies that are neither spiral or elliptical

Milky Way Part of the galaxy cluster called the Local Group Contains the Sun The Milky Way is our galaxy. It looks “milky” because the stars are too close together to be seen individually.