Astronomy Tour of the known universe Astronomy - the study of the objects that lie beyond our planet Earth – the only planet known to host life as we know it. About Earth and the processes by which these objects interact with one 406,000 km from earth is the only earth’s natural satellite – the another. moon. Universe - the name that we use to refer to the collection of all Earth the things that exist in space. Tour of the known universe Moon Astronomers try group objects in the universe using relationships that may connect objects together such as gravitational attraction and relative velocities as a way of systematic organization and presentation. Planet Solar System The solar system – the sun, planets, dwarf planets, asteroids, Interstellar Neighborhood meteors, comets and space of about 143.73 billion km from the sun. Milky Way Galaxy Solar System Local Galactic Group Virgo Supercluster Local Supercluster - Laniakea The Observable Universe Astronomy Tour of the known universe Interstellar neighborhood – the region within about 32.6 The milky way galaxy - gravitationally bound system of about lightyears around the sun, it contains the alpha centauri which is 200 billion stars, stellar remnants, interstellar gas, dust, and dark the nearest star on earth apart from the sun as well as sirius A matter and the space of about 50, 000 lightyears from its center which is the brightest star seen on earth sky. Interstellar Neighborhood Milky Way Galaxy Astronomy Tour of the known universe The local galactic group – gravitationally bound clusters of The Virgo supercluster – gravitationally bound clusters of about galaxies of about 5 million lightyears that includes the Milky Way 47 000 galaxies and has a radius of about 55 million lightyears, it galaxy. includes the local group and Virgo. Local Galactic Group Virgo Supercluster Astronomy Tour of the known universe The local super cluster also called laniakea supercluster – The observable universe – the galaxies and space within about clusters of about 100 000 galaxies and a radius of about 260 46.5 billion light-years in any direction from earth of which we are million light years, local super clusters are grouped according to able to detect electromagnetic signals relative velocities and not by gravitational attraction. Local super cluster - Laniakea The Observable Universe .