Related topics: universe · dark matter · galaxies · white dwarfs · big bang

Video: The making of the largest 3-D map of the universe

DESI, the Dark Energy Spectroscopic Instrument, will mobilize 5,000 swiveling robots – each one pointing a thin strand of fiber-optic cable – to gather the light from about 35 million galaxies.

Mapping historical changes in dark matter

Combining Einstein's theory of relativity with one of the most powerful telescopes in the world has helped an international team of researchers measure where and how dark matter structures grow in the universe. Their analysis ...

Team puts forth ideas on the nature of dark matter

Dark energy and dark matter comprise 96 percent of the total mass of the universe. Two main hypotheses about the nature of dark matter are presently debated. One posits that dark matter consists of massive compact halo objects; ...

The sun in 2018

This montage of 365 images shows the changing activity of our sun through the eyes of ESA's Proba-2 satellite during 2018. The images were taken by the satellite's SWAP camera, which works at extreme ultraviolet wavelengths ...

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Dark energy

In physical cosmology and astronomy, dark energy is a hypothetical form of energy that permeates all of space and tends to increase the rate of expansion of the universe. Dark energy is the most popular way to explain recent observations that the universe appears to be expanding at an accelerating rate. In the standard model of cosmology, dark energy currently accounts for 74% of the total mass-energy of the universe.

Two proposed forms for dark energy are the cosmological constant, a constant energy density filling space homogeneously, and scalar fields such as quintessence or moduli, dynamic quantities whose energy density can vary in time and space. Contributions from scalar fields that are constant in space are usually also included in the cosmological constant. The cosmological constant is physically equivalent to vacuum energy. Scalar fields which do change in space can be difficult to distinguish from a cosmological constant because the change may be extremely slow.

High-precision measurements of the expansion of the universe are required to understand how the expansion rate changes over time. In general relativity, the evolution of the expansion rate is parameterized by the cosmological equation of state. Measuring the equation of state of dark energy is one of the biggest efforts in observational cosmology today.

Adding the cosmological constant to cosmology's standard FLRW metric leads to the Lambda-CDM model, which has been referred to as the "standard model" of cosmology because of its precise agreement with observations. Dark energy has been used as a crucial ingredient in a recent attempt to formulate a cyclic model for the universe.

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