What is Dark Energy?

More is unknown than is known. We know how much dark energy there is because we know how it affects the Universe’s expansion. Other than that, it is a complete mystery. But it is an important mystery. It turns out that roughly 70% of the Universe is dark energy. Dark matter makes up about 25%. The rest – everything on Earth, everything ever observed with all of our instruments, all normal matter – adds up to less than 5% of the Universe. Come to think of it, maybe it shouldn’t be called “normal” matter at all, since it is such a small fraction of the Universe.

 Researchers have come up with a 3D map of the sky, which facilitates scientists to look into the time six billion years ago when dark energy became a dominant influence on the Universe’s expansion.

Universe Dark Energy-1 Expanding Universe This diagram reveals changes in the rate of expansion since the universe's birth 15 billion years ago. The more shallow the curve, the faster the rate of expansion. The curve changes noticeably about 7.5 billion years ago, when objects in the universe began flying apart as a faster rate. Astronomers theorize that the faster expansion rate is due to a mysterious, dark force that is pulling galaxies apart. NASA/STSci/Ann Feild

Using the new data, astronomers have been able to measure the exact distance to over a quarter of a million galaxies to gain new understanding of the key period in cosmic history. The discovery that everything in the cosmos is moving apart at a faster and faster rate was one of the major breakthroughs of the 20th Century, and the BOSS survey is a step to examine this phenomenon.The quality of the BOSS map is phenomenal and is a  big step forward on all previous such surveys.
It provides details on the position of galaxies out to some six billion light-years from Earth and gives those measurements to within 1.7 percent of their expected true value.
BOSS uses two techniques to understand the Universe’s acceleration, the first one of them is baryon acoustic oscillations.

These oscillations  are pressure-driven waves that passed through the very early Universe and which were imprinted on the distribution of matter once conditions had cooled below a certain point.
The other technique involves “redshift space distortions”. These describe the component in the velocity of galaxies that stems from the growth of structure in the Universe. The team can see if neighbouring galaxies are clustering in the way that would be expected from the action of gravity.
The BOSS project, which acquires all its data using the 2.5m Sloan telescope at Apache Point Observatory in New Mexico, is only a third complete and will continue to map the 3D positions of galaxies.

Lets see what the future holds for us.

Links and Sources:

Indiatimes

NASA

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