Hubble sweeps us off our feet again. Using the orbiting 94-inch telescope astronomers have taken the deepest photo of the universe yet. They’re calling it the Hubble Xtreme Deep Field or XDF. It’s based on the older Ultra Deep Field picture made in 2003-2004 of a tiny patch of sky southwest of Orion in the constellation Fornax the Furnace measuring 3 arc minutes or one-tenth the size of the full moon. That picture took 11 1/2 days to expose (1 million seconds) and recorded light from galaxies only a stone’s throw from the Big Bang.
This new image drills into the original ultra deep field, adding another million seconds of exposure time and squeezing even more galaxies from a smaller 2.3 x 2 arc minute peephole. And yes, it takes our cosmic gaze back another 200 million years.
The faintest galaxies in the photo are ten billion times fainter than the dimmest star the human eye can see. For those familiar with star magnitudes, a measure of celestial brightness, the picture reaches down to magnitude 31. The picture resembles a sandwich piled high with slice upon slice of time, sampling relatively nearby space as well as the most distant recess of the universe we’ve seen yet.
Some of the galaxies are so far away we see them when the universe was less than 5% of its current age.
See all those tiny blue “stars” peppering the image? They’re young, small galaxies – seeds as it were – that later merged with similar small galaxies to build the stately spiral and monster elliptical galaxies we see in the current era. The blue color comes from fresh generations of blazingly hot blue stars formed in the violence of collision and subsequent star birth.
The large, fuzzy red galaxies are what’s left of collisions between earlier galaxies that failed to ignite new star formation. Their color tells us that their stars are aging. There’s even a smattering of beautiful spiral galaxies similar to our own Milky Way. The farthest objects are 13.2 billion light years away and formed 450 million years after the origin of the univers in the Big Bang.
“The XDF is the deepest image of the sky ever obtained and reveals the faintest and most distant galaxies ever seen. XDF allows us to explore further back in time than ever before,” said Garth Illingworth of the University of California at Santa Cruz, principal investigator of the Hubble Ultra Deep Field 2009 program.
A few days ago we looked backward in time through the lens of a huge boulder dropped by a glacier 10,000 years ago. Hubble transports us to a time when Earth was still an unrealized possibility.