What is Hubble Deep Field?
[[File:HubbleDeepField.800px.jpg|thumb|right|300px|A high resolution version of The Hubble Deep Field]] The '''Hubble Deep Field''', sometimes called the '''HDF''', is an image of a small part of the night sky. The image was taken in the direction of the [[constellation]] [[Ursa Major (constellation)|Ursa Major]] by the [[Hubble Space Telescope]] in [[1995]]. It is important because it shows some of the earliest (farthest away) [[galaxies]] ever seen, over 3000 in total. The area of the sky the HDF was taken in makes up less than 1/10th the width of a full [[Moon]], yet it contains over 3,000 galaxies.<ref>{{cite web|url=http://hubblesite.org/newscenter/archive/releases/1996/01/|title=Hubble's deepest view of the Universe unveils bewildering galaxies across billions of years. |publisher=Hubblesite.org}}</ref> Because of the time it takes for [[light]] from these galaxies to reach [[Earth]], many in the picture look exactly as they did over 10 billion (10,000,000,000) years ago. Because of this it allows scientists to look at what the [[Universe]] was like at that time, and how it changed to become what it is now. Add to this the [[cosmological principle]], which suggests that on large scales the Universe is roughly the same no matter what direction you look,<ref>{{cite web|url=http://csep10.phys.utk.edu/astr162/lect/cosmology/cp.html|title=The Cosmological Principle|publisher=phyicss_uk.edu}}</ref> and the HDF becomes a very important tool for [[astronomer]]s studying how the Universe has changed. For these reasons the HDF is sometimes called 'the most important image ever taken'.<ref>{{cite web|url=http://www.google.co.uk/search?hl=en&safe=off&rlz=1T4RNWE_enGB313GB313&q=hubble+deep+field+most+important+image+ever+taken&meta=&aq=0&oq=hubble+deep+field+most+important|title=Google search:Hubble Deep Field}}</ref> ==Related pages== * [[Hubble Ultra Deep Field]] * [[Hubble Extreme Deep Field]] * [[Hubble Space Telescope]] == References == {{reflist}} [[Category:Cosmology]] [[Category:Galaxies]]