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
The gravity of distant objects can distort and magnify light creating a gravitational lens The result can be a circular ring of light around a celestial object right billions of years Our universe is now approximately 13 8 billion years old These very distant galaxies formed in the universe's first 1 billion years Astronomers are looking for the first galaxies that lit up our cosmos Every year they break their distance records New technology lets them collect older light Look to the Light Light is astronomy's crucial messenger Many types of light exist and each kind has a certain energy depending on its wavelength To visualize what wavelength is imagine two people holding a string loosely between them One person starts moving his arm up and down to create a wave The distance from one peak of the string's wave to the next peak is the wave's wavelength Light s Wavelength dictates what type of light it is The kind of light human eyes can see ranges from red light to violet The colors vary based on wavelength But beyond the narrow band of wavelengths we can see light also comes in forms we cannot see All types of light fall along what is called the electromagnetic
10 12 10 1 nanometer 104 1 micron 10 1 millimeter 10 1 meter 10 1 kilometer X ray Microwave Gamma rays traviolet WWWWWWWWWWWWWWWWVVSS Visible light Visible light only occupies a narrow sliver of the electromagnetic spectrum How do the wavelengths of different types of light compare Red has a longer wavelength than violet Infrared light has a longer wavelength than red light Microwaves and radio waves have even longer wavelengths Longer wavelength light carries less energy than shorter wavelength light Several types of light have shorter wavelengths than we can see with the naked eye Ultraviolet light X rays and gamma rays are all included in this group These types of light carry a great deal of energy They are often associated with high energy events in space such as massive explosions Astronomers have developed tools to observe many different wavelengths of light in space Spying Light from Galaxies The light from galaxies reveals their distances To study a galaxy astronomers examine its light in many wavelengths If that galaxy appears to be moving toward Earth astronomers see its light get a bit bluer in color Its light is shifted to smaller wavelengths If the galaxy appears to be moving away from us the light is a bit redder It has longer wavelengths These color changes happen for the same reason you hear a slightly higher pitched sound from a train or ambulance coming toward you than you do when it is moving away This phenomenon is called the Doppler
