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Celestial Tour: Long Ago and Far Away

Celestial Tour: Long Ago and Far Away

 We see distant galaxies not as they are today, but as they were many millions and even billions of years ago. 


Celestial Tour: Long Ago and Far Away: Video Segments
Credits

Produced by the Space Telescope Science Institute’s Office of Public Outreach in collaboration with NASA’s Universe of Learning partners: Caltech/IPAC, Center for Astrophysics | Harvard & Smithsonian, NASA Jet Propulsion Laboratory, and Sonoma State University 

Transcript

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 [NEW-AGE MUSIC] 


(DESCRIPTION) 
 Heavenly bodies glow in the night sky 


Text, Looking deep into the universe, we see a dazzling array of celestial bodies. 


We see them at vast distances both in space and in time 


Text, Long Ago and Far Away 


detailed photograph of the moon 


Text, The moon is Earth's nearest neighbor in space and the farthest humans have travelled into the universe 


Photo of astronaut planting American flag on the moon 


Moon and Earth 


Text, This image from the Voyager spacecraft is the first ever to capture both Earth and Moon in a single frame 


They are celestial companions in a seemingly dark and empty cosmos. 


However, they are not as close as this picture might suggest. 


A tiny earth to the left edge, tinier moon to the right, separated by a vast, black expanse. 


The true scale between Earth and the Moon looks more like this: 


Earth's diameter is roughly four times the Moon's diameter. 


Their separation is just over 30 times the Earth's diameter 


30 Earths appear between the Earth and Moon 


This distance is approximately 230,000 miles. 


squiggly line moves from the Earth toward the moon 


Even at the speed of light, it takes about one and a quarter seconds to travel from Earth to the Moon. 


This fact explains the two-and-a-half second delay in radio conversations between Mission Control and Apollo astronauts on the Moon 


Picture of Mission Control on the left, astronaut on the moon on the right 


Astronomers use light-travel time as a measure of distance. In these units, the Moon is 1.28 light-seconds away from Earth. 


Light travel time has proven to be the most useful distance measure of the universe. 


For example, the moon's orbit stretches across two and a half light-seconds of space, while the Sun itself is more than four light-seconds in diameter, and is located about 500 light-seconds away, which is more than 8 light-minutes 


Circle with "Earth" written in the center, a small dot labeled "moon" on the perimeter, and the sun illustrated as a gigantic yellow ball. 


Earth shown as a tiny dot to the left of the screen, Sun a slightly larger yellow dot to the right 


Sun shown through a powerful telescope 


because of this light-travel time, we see eruptions on the sun more than eight minutes after they happen 


illustration of dot surrounded by widening circles labeled with names of planets 


The size of the solar system, several billion miles across, is measured in light-hours 


Telescopic photo of Neptune 


It takes at least four hours for light from Neptune to reach Earth 


Much farther away are the stars 


Telescopic photo of many, many stars in the night sky 


Alpha Centauri and Proxima Centauri are circled on the photo 


Alpha Centauri is the nearest bright start, but slightly closer is the faint dwarf star Proxima Cenauri 


Even from these nearest of stars, the light-travel time is over 4 years. 


Telescopic photo of the Milky Way 


Our Milky Way Galaxy is a giant pinwheel of some hundred billion stars 


The Sun is located about 24 thousand light-years from the galaxy's center. 


A star within our galaxy might explode today, and we wouldn't know about it until many thousands of years later. 


The nearest large neighbor to our Milky Way is the Andromeda Galaxy 


The light we see today was emitted by stars in Andromeda about two and a half million years ago, during the time of our early human ancestors roamed Africa 


Telescopic map of known galaxies 


Galaxies can gather together in vast clusters 


This grouping is at the center of the Virgo Cluster of galaxies 


The entire Virgo Cluster contains many thousands of galaxies. It is the largest nearby galaxy cluster. 


Located over 60 million light-years away, these galaxies appear to us as they were at the end of the age of the dinosaurs on Earth 


Such long light-travel times mean that a telescope looking out into space is also looking back in time 


We see distant galaxies not as they are today, but as they were many millions and even billions of years ago. 


To look deep into the universe, astronomers must take long exposures, collecting light for many hours or days. 


Deeper exposures reveal fainter features and greater detail. Here is a series of images of the Andromeda Galaxy exposed for 1, 5, 30, and 45 minutes. 


image on the right side of the screen slowly blooms from a blurry white smudge into a large, swirling galaxy 


Photo taken with the Hubble telescope, showing celestial bodies as orange, yellow, blue, red, and white lights 


The deepest visible-light exposure ever taken is the Hubble Ultra Deep Field. This observation lasted more than eleven days. Some 10 thousand galaxies can be seen in this image. 


All these galaxies are found in a tiny region of the sky. about the same apparent size as the Sea of Serenity on the Moon as seen from Earth 


galaxies in such deep images are typically many billions of light-years away. 


What appears to be a 2D image is actually a 3D collection of galaxies 


Flat image rotates and spreads out showing a timeline of 1, 3, 5, and 10 billion light years 


Nearby spiral galaxies, seen in the recent past, show well developed pinwheel shapes 


More distant galaxies, seen as they were several billion years ago, are smaller and have incomplete spiral structure 


The most distant galaxies, seen as they were many billions of years ago, are tiny and just beginning to develop their spiral shapes. 


Assembling them together, one can visually examine the history of galaxy evolution. Looking billions of light-years out into space, we see billions of years back in time. 


photos of galaxies labeled present to 3 billion years ago, 3 to 7 billion years ago, and 7 to 10 billion years ago 


Humans have traveled a mere one light-second into the universe. But even that tiny distance grants us a whole new perspective 


Observations from the Hubble Space Telescope can take us across billions of light-years. 


A journey through the Hubble Ultra Deep Field, across both space and time, takes us to galaxies long ago and far away 


Stars and galaxies float by 


Produced by: Space Telescope Science Institute, Office of Public Outreach. Photo credits. 


For more information, visit Hubble Site: http://hubblesite.org/newscenter/archive/releases/2004/07/. The Space Telescope Science Institute is operated by the Association of Universities for Research in Astronomy, Inc., for NASA under contract with NASA's Goddard Space Flight Center, Greenbelt, Maryland.