NASA and the U.S. Department of Energy (DoE) have teamed up to operate the future Joint Dark Energy Mission (JDEM). As you probably know, recent astronomical measurements have showed that about 72% of the total energy in the universe is dark energy, even if scientists don't know much about it, but speculate that it is present almost since the beginning of our Universe more than 13 billion years ago. The JDEM 'mission will make precise measurements of the expansion rate of the universe to understand how this rate has changed with time. These measurements will yield vital clues about the nature of dark energy.' The launch of a spacecraft for the JDEM mission is not planned before 2015. Read more...
Before going further, let's look at a timeline of the Universe. You can see above "a representation of the evolution of the universe over 13.7 billion years. The far left depicts the earliest moment we can now probe, when a period of "inflation" produced a burst of exponential growth in the universe. (Size is depicted by the vertical extent of the grid in this graphic.) For the next several billion years, the expansion of the universe gradually slowed down as the matter in the universe pulled on itself via gravity. More recently, the expansion has begun to speed up again as the repulsive effects of dark energy have come to dominate the expansion of the universe. The afterglow light seen by WMAP was emitted about 380,000 years after inflation and has traversed the universe largely unimpeded since then. The conditions of earlier times are imprinted on this light; it also forms a backlight for later developments of the universe." (Credit: NASA/WMAP Science Team) Here is a link to various other formats of this image.
The picture on the left shows that "WMAP data reveals that its contents include 4.6% atoms, the building blocks of stars and planets. Dark matter comprises 23% of the universe. This matter, different from atoms, does not emit or absorb light. It has only been detected indirectly by its gravity. 72% of the universe, is composed of "dark energy", that acts as a sort of an anti-gravity. This energy, distinct from dark matter, is responsible for the present-day acceleration of the universal expansion. WMAP data is accurate to two digits, so the total of these numbers is not 100%. This reflects the current limits of WMAP's ability to define Dark Matter and Dark Energy." (Credit: NASA/WMAP Science Team) Here is a link to various other formats of this image.
Now, let's return to the NASA's news release mentioned in the introduction. "'Understanding the nature of dark energy is the biggest challenge in physics and astronomy today,' said Jon Morse, director of astrophysics at NASA Headquarters in Washington. "JDEM will be a unique and major contributor in our quest to understand dark energy and how it has shaped the universe in which we live.' One of the most significant scientific findings in the last decade is that the expansion of the universe is accelerating. The acceleration is caused by a previously unknown dark energy that makes up approximately 70 percent of the total mass energy content of the universe. This mission has the potential to clarify the properties of this mass energy. JDEM also will provide scientists with detailed information for understanding how galaxies form and acquire their mass."
Here is a link to the JDEM website and another one about Dark Energy Science which provides additional details. "Whatever it is, modern astronomical measurements show that about 72% of the total energy in the universe is dark energy. The rest consists of dark matter (23%) and the familiar atomic matter that makes up our bodies (4.6%). Not knowing the nature of dark energy would be akin to an alien scientist trying to understand Earth's surface without knowing the nature of water. Scientists cannot claim to understand the universe at its deepest level if they can't explain its dominant form of energy. Unlocking the mysteries of dark energy will have profound implications for both physics and astronomy." The JDEM site suggests that scientists have developed too many possible solutions about this dark energy mystery.
I've mentioned above the WMAP acronym which stands for the Wilkinson Microwave Anisotropy Probe which is "a NASA Explorer mission. It has produced a wealth of precise and accurate cosmological information. WMAP produced the first full-sky map of the microwave sky with a resolution of under a degree, about the angular size of the moon. The patterns in the map result from well-understood physical processes that happened when the universe was young. By matching the patterns in the map to the physics we know, WMAP has produced a convincing consensus on the contents of the universe, erasing lingering doubts about the existence of dark energy, and severely limiting the density of hot dark matter. WMAP has determined the age of the universe, the epochs of the key transitions of the universe, and the geometry of the universe, while providing the most stringent data yet on events in the first fraction of a second of the universe."
As you'll see on this page, Wilkinson Microwave Anisotropy Probe (WMAP) was launched in June of 2001 and has made a map of the temperature fluctuations of the cosmic microwave background (CMB) radiation, with higher resolution, and accuracy than previous satellites. For more information, please visit the WMAP image gallery.
And good luck to the JDEM team! Let's hope it gets the expected funds...
Sources: NASA news release, November 19, 2008; and various websites
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