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| This picture is the reason the Hubble Space Telescope was built. It has been compared in significance to the Dead Sea Scrolls and the discovery of the structure of DNA. It is the deepest and farthest back in time that humans have ever been able to see, almost back to the beginning of time. | |||
| In some sense, HST is like a time machine. Because light travels at a finite speed, the light from distant galaxies takes years to reach us. We are seeing some of these galaxies as they appeared billions of years ago, when the universe was only about 5% of its current age. This is of course before the Earth, the Sun, or even our own galaxy ever existed. | The speed of light is 186,262 miles, or 300,000 kilometers, per second | ||
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| The universe is probably about 12-15 billion years old, so we are looking back to a time when the universe was only a few hundred million years old. Of course we also see everything else in our line of sight. Some of the galaxies in the picture are closer to us and so we are seeing them as they appeared more recently. Now the task before astronomers is to figure out which galaxies in the picture are the farthest from us, and so from the earliest time in the universe. | |||
| We can use statistical arguments to guess at this information from the color and magnitude, or brightness of the galaxies. The light from these galaxies has been highly redshifted because of the expansion of the universe, so the reddest, faintest galaxies are more likely to be the farthest from us. | |||
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| Astronomers know very little about galaxies in the early universe. Until HST made it possible to image them, we could only infer details about them from observations of present day galaxies. This is like taking a picture of a child and from it trying to figure out what its parents look like. But now that we have direct observations, this is a field in revolution. HST is causing us to re-evaluate what we know about the appearance and evolution of galaxies. | |||
| The picture of the Hubble Deep Field is remarkable not only in its content and beauty, but skill involved in preparing it. A new method of image processing, called "drizzling" was used to produce the image, allowing it to be sharper than ever before possible. Though I have been calling it "a picture" it was created from 342 separate images taken by the telescope taken over many days. By electronically "stacking up" almost 300 of these pictures we are able to see deeper than any one picture would allow. Because this adds up light so fast, astronomers had to be careful to choose a tiny region of the sky that had almost no stars from our galaxy and no galaxy clusters. Without the clutter and glare of brighter nearby objects we are able to see some galaxies as faint as 30th magnitude, or about 4 billion times fainter than you can see with the naked eye. | (You can read a technical description of drizzling on the STScI Web site). | ||
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| The Hubble Deep Field is so significant that it was given immediately
to the astronomical community at large so that astronomers all over the
world could study it. By doing so they can help to answer some of the
fundamental questions in astronomy: How many galaxies are there? How do galaxies form? How do they interact? Are galaxies randomly distributed or do they they pile up in cosmic walls or sheets? How much mass is there in the universe? Will the universe expand forever, or end in a "big crunch" into a black hole? Is spacetime fundamentally curved or flat? Is space infinite? |
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Additional Resources |
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Official Images at STScI |
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| Text © 1997 Andy Howell All Rights Reserved
Hubble Space Telescope images are the intellectual property of the Space Telescope Science Institute, operated by the Association of Universities for Research in Astronomy, Inc., from NASA contract NAS5-26555, and are reproduced with permission from AURA/STScI. | ||
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Full WFPC2 Mosaic
Hubble Deep Field Wide View
