The Wilkinson Microwave Anisotropy Probe (WMAP) has, quite literally, changed our view of the Universe. And after nine years of mapping the slight temperature variations in the cosmic microwave background (CMB) radiation, its job is done and NASA has commanded the probe to fire itself into a "graveyard orbit" around the sun.
Launched in 2001, this ground-breaking spacecraft set out to unravel some of the most fundamental questions in modern cosmology. How old is the Universe? What happened when the Universe was born?
Before WMAP, scientists knew the Universe was expanding, they even had a ballpark figure of how old the Cosmos might be - somewhere between 8 to 20 billion years. However, the details were somewhat sketchy.
Then WMAP came along and it began its nine-year study to create a full-sky survey of the very tiny variations in temperature of the "afterglow" of the Big Bang.
The young Universe was very hot, so hot in fact that its heat still pervades the entire sky. But this ancient echo of electromagnetic radiation is extremely weak with a temperature hovering just above absolute zero - 2.725 Kelvin.
The probe was so sensitive to this echo that it could detect very slight variations - or "anisotropies" - in the CMB radiation. These variations are the fingerprints of the birth of our Universe revealing the conditions at the start of time, moments after the Big Bang.
As a result of this survey, a mind-bogglingly precise measurement on the age of the Universe was found. The magic number turned out to be 13.75 billion years (plus or minus 0.11 billion years).
But WMAP didn't stop there. Although scientists have hypothesized that the Universe went through rapid inflation just after the Big Bang, WMAP has managed to find even more supporting evidence that this growth spurt did happen. Thanks to WMAP, we also know that a mysterious entity called Dark Energy fills 72 percent of the Cosmos and Dark Matter makes up for around 23 percent. "Normal" baryonic matter makes up for a piddly 4.6 percent of the observable universe.
WMAP has not only given us the ability to understand the nature of the Universe in its entirety, but it has acted like a time machine, deriving the nature of the Big Bang, early Universe and how the Cosmos evolved over 13.75 billion years of existence.
Image: WMAP three year picture of the infant universe. Colors indicate "warmer" (red) and "cooler" (blue) spots. The white bars show the "polarization" direction of the oldest light. This new information helps to pinpoint when the first stars formed and provides new clues about events that transpired in the first trillionth of a second of the universe (NASA / WMAP Science Team)