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| Poster Version | Figure 1 | Figure 2 |
This is an image from NASA's Spitzer Space Telescope of stars and galaxies
in the Ursa Major constellation. This infrared image covers a region of
space so large that light would take up to 100 million years to travel
across it. Figure 1 is the same image after stars, galaxies and other
sources were masked out. The remaining background light is from a period
of time when the universe was less than one billion years old, and most
likely originated from the universe's very first groups of objects --
either huge stars or voracious black holes. Darker shades in the image on
the left correspond to dimmer parts of the background glow, while yellow
and white show the brightest light.
Brief History of the Universe
In figure 2, the artist's timeline chronicles the history of the universe,
from its explosive beginning to its mature, present-day state.
Our universe began in a tremendous explosion known as the Big Bang about
13.7 billion years ago (left side of strip). Observations by NASA's Cosmic
Background Explorer and Wilkinson Anisotropy Microwave Probe revealed
microwave light from this very early epoch, about 400,000 years after the
Big Bang, providing strong evidence that our universe did blast into
existence. Results from the Cosmic Background Explorer were honored with
the 2006 Nobel Prize for Physics.
A period of darkness ensued, until about a few hundred million years
later, when the first objects flooded the universe with light. This first
light is believed to have been captured in data from NASA's Spitzer Space
Telescope. The light detected by Spitzer would have originated as visible
and ultraviolet light, then stretched, or redshifted, to lower-energy
infrared wavelengths during its long voyage to reach us across expanding
space. The light detected by the Cosmic Background Explorer and the
Wilkinson Anisotropy Microwave Probe from our very young universe traveled
farther to reach us, and stretched to even lower-energy microwave
wavelengths.
Astronomers do not know if the very first objects were either stars or
quasars. The first stars, called Population III stars (our star is a
Population I star), were much bigger and brighter than any in our nearby
universe, with masses about 1,000 times that of our sun. These stars first
grouped together into mini-galaxies. By about a few billion years after
the Big Bang, the mini-galaxies had merged to form mature galaxies,
including spiral galaxies like our own Milky Way. The first quasars
ultimately became the centers of powerful galaxies that are more common
in the distant universe.
NASA's Hubble Space Telescope has captured stunning pictures of earlier
galaxies, as far back as ten billion light-years away.
