ONE GOING THE DISTANCE le live on a planet that along with seven other planets and countless smaller V bodies orbits the sun Our sun is one of approximately 200 billion stars in the Milky Way galaxy and most of those stars appear likely to host planets of their own Our galaxy is just one island of lights in the universe s vast sea of hundreds of billions of galaxies Each galaxy is made up of billions of individual stars Astronomy is the study of all the objects that make up the universe outside Earth from the planets and comets in our solar system to the many types of stars in galaxies that are sprinkled across the universe To learn about these celestial objects astronomers study them using telescopes and other scientific instruments Because current technology makes it impossible to leave the Milky Way the only images showing the whole galaxy at once are artists impressions
A telescope is a time machine The Modern astronomers see Andromeda as it appeared 2 5 million years ago when humans were first evolving on Earth light it collects from objects in space has a specific speed limit Light cannot Like a magnifying Glass in Space travel faster than 186 282 miles per second 299 792 kms That means when an astronomer uses a telescope to observe a distant galaxy she studies light that has taken a long time to travel to Earth Astronomers measure a distance in space by how Astronomers can use a trick of gravity to find distant galaxies Anything in the universe that has mass a galaxy a star even a planet warps the space around it The biggest cosmic structures such as clusters of hundreds of galaxies have so much mass their gravity has a major impact on nearby matter and light When the light from a distant galaxy passes the galaxy cluster the light changes direction due to the warped space If the distant galaxy the laxy cluster and an observer using a telescope al lay along a line that light is bent just right so it gives the astronomer a magnified view of the distant galaxy The galaxy cluster acts like a giant magnifying glass space These alignments make it possible for astronomers to find many distant galaxies and stars long light takes to travel that distance One light year is the distance light travels in one Earth year It is approximately 5 9 trillion miles 9 5 trillion km The nearest large galaxy to ours is the Andromeda Galaxy It is 2 5 million light years away This means when astronomers turn a telescope to this galaxy visible from the Northern Hemisphere they see light that left Andromeda approximately 2 5 million years ago The scale of our solar system is much smaller The moon is approximately 1 3 light seconds away and the sun is approximately eight light minutes away The most distant planet Neptune is approximately four light hours from the sun Some scientists study nearby galaxies such as Andromeda but others research the more distant galaxies that lie much farther from Earth The light that left these galaxies has been traveling for 6
