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Hubble eXtreme Deep Field: a new, improved portrait of mankind's deepest-ever view of the Universe
Original Announcement => Farthest View Ever of the Universe: Hubble eXtreme Deep Field
Hubble Space Telescope: Deepest View Ever of the Universe
This is an extraordinary accomplishment and webinar. The public was invited to participate in a "Meet the Hubble eXtreme Deep Field Observing Team" webinar, where three key astronomers of the XDF observing team described how they assembled the landmark image and explained what it tells us about the evolving universe. The webinar begins at 4:00 in video below.
Ray Villard (STScI) introduced and moderated the panel. The team present were Garth Illingworth, Dan McGee, and Pascal Oesch, all from University of California Santa Cruz. Each presented background and procedures on the eXtreme Deep Field image. Some notable concepts, facts, and quotes are below the video.
Hubble eXtreme Deep Field: Some Notable Concepts, Facts, Quotes
Ultimately the search is for the first galaxies. XDF is key to understanding the origins of galaxies, the search for the first galaxies, when and how did galaxies form and grow, how the Milky Way and Andromeda formed.
Hubble is a time machine: XDF sees galaxies forming 13.2 billion years ago, 450 million years after the Big Bang, and sees back in time through 96% of the life of the Universe.
Galaxies earlier than 800 million years after the Big Bang can only be seen in infrared light. XDF reveals these galaxies unseen in deepest visible-light Hubble Utra Deep Field images.
Hubble is at its limit of detection, for finding any earlier galaxies (400 million years after the Big Bang). The James Webb Space Telescope (JWST) will discover the first galaxies and probably the first stars. The gain in efficiency and resolution will be a factor of 100 with the JWST and will be "astonishingly powerful". The project is working towards a 2018 launch date.
The Universe is basically the same in any direction, is symmetric. No asymmetries have been detected.
XDF is full of galaxies and there might be even more fainter galaxies beyond the image that cannot be currently seen. There are more galaxies, and fainter galaxies, in the image than expected beforehand. The Universe is full of tiny, little galaxies in the early times that are building up.
The numbers of galaxies, in redshift 12 to 15, is estimated to decrease. The number of galaxies probably increased around redshift 10. Beyond the redshift is the cosmic glow, the cosmic microwave background, from the Big Bang.
Very small gravitational lensing effect in XDF. Galaxy clusters and very large galaxies were avoided which cause this effect. There is tiny "weak lensing" effect in image.
The age of the galaxy images, particularly using powerful microwave telescopes, has been determined independently. Beyond the scope of the XDF to determine.
XDF is not designed to search for or detect dark energy or dark matter. Supernova searches originally detected dark energy. Galaxy cluster and weak lensing large-scale observations originally detected dark matter.
Deep in the XDF image, the early galaxies are smaller with more intense light and much closer together. The Universe was a tenth (1/10) if its size now. Presumably these galaxies would build up to larger current galaxies such as the Milky Way and Andromeda. The early galaxies are the seeds from which current galaxies evolved. These early galaxies grew, collided, merged in a very dynamic and dramatic process.
The cosmic microwave background was about 400,000 years after the Big Bang, very soon afterwards. The limit of the XDF is 400 million years after the Big Bang. Perhaps first galaxies formed about 150 to 200 million years after the Big Bang. Perhaps the first stars came together about 100 - 150 million years after the Big Bang. Before that were the Dark Ages. The first stars and galaxies ended the Dark Ages.
The earliest galaxies observed are moving away from each other as the Universe expands, increasingly separating from each other. A small fraction of these galaxies were pulled towards each other by gravity, if close enough. The example of the expanding balloon with dots on it...
XDF and Hubble cannot detect individual stars within the early galaxies. The James Webb Space Telescope (JWST) probably will not be able to either and therefore will not be able to detect the individual "first stars". The JWST will probably be able to detect early supernova, however.
XDF is really about galaxies and not about the formation of the Universe itself. A major change in the Universe occurred from about a few hundred million years to 900 million years after the Big Bang. The change from neutral hydrogen to ionized hydrogen in the Universe and within the XDF time frame was most likely caused by the galaxies. XDF will not add significantly to cosmology, however.