New Method Discovered to Detect and Measure Dark Energy Using Milky Way and Andromeda Galaxies
Researchers from the University of Cambridge have made a groundbreaking discovery in the study of dark energy, the mysterious force that accounts for more than two-thirds of the universe. By examining the motion between the Milky Way and Andromeda galaxies, scientists believe they may have found a new way to measure and potentially detect dark energy.
Dark energy is responsible for the accelerating expansion of the universe. Scientists have been studying it since its discovery in the late 1990s, using distant galaxies. However, they have yet to directly detect it. This new research suggests that by focusing on the motion of Andromeda, the neighboring galaxy on a collision course with the Milky Way, dark energy may be detected and measured.
The researchers found that by studying the collective mass and movement of the two galaxies as they move towards each other, they can estimate the upper value of the cosmological constant, which is a simple model of dark energy. The upper limit they found is five times higher than values determined from studying the early universe.
“While the technique is still in its early stages, it holds great potential for detecting dark energy in our own cosmic neighborhood,” said the researchers. The results of their study have been published in The Astrophysical Journal Letters.
Currently, only five percent of the observable universe is visible to us. Scientists believe that about 27% of the universe is made up of dark matter, which holds objects together, while a staggering 68% is dark energy.
Dark energy is described as a family of models that can be added to Einstein’s theory of gravity. The simplest version is known as the cosmological constant, a constant energy density that pushes galaxies apart. Einstein initially added the cosmological constant to his theory of general relativity temporarily. However, it was later discovered that dark energy was responsible for the universe’s accelerated expansion.
Detecting dark energy has always been a challenge due to its nature. Astronomers have primarily focused on studying objects from the early universe and measuring their movement away from us. However, this new research highlights that the region of the universe most sensitive to dark energy may be closer than we realized – our cosmic backyard.
The Andromeda galaxy, being the closest to our Milky Way, is said to be on a slow-motion collision course with our galaxy. As the two galaxies draw closer to each other, they will start to orbit each other at a slow pace. By studying the mass and movement of Andromeda, scientists hope to gain insights into the cosmological constant and dark energy.
“The fact that Andromeda is not running away from us makes it an ideal candidate for studying dark energy,” said Dr. David Benisty, the study’s first author.
The researchers used simulations based on the best available estimates of the mass of both galaxies to study the effects of dark energy on their movement. By changing the value of the cosmological constant in their model, they were able to observe how it affected the orbit of the two galaxies. The upper limit they determined is about five times higher than what can be measured from the rest of the universe.
Although the technique is not a direct detection of dark energy, it has the potential to be immensely valuable. The researchers believe that more accurate measurements of Andromeda’s mass and motion from future telescopes, such as the James Webb Telescope (JWST), could help refine the technique and reduce the upper bounds for the cosmological constant.
“Dark energy remains one of the biggest puzzles in cosmology,” said Dr. Benisty. “We hope that this technique could help unravel its mystery by studying other pairs of galaxies and refining our understanding of how dark energy affects the universe.”
In conclusion, this new method of studying the motion between the Milky Way and Andromeda galaxies provides a promising avenue for detecting and measuring dark energy. Further research and advancements in technology are anticipated to shed more light on this enigmatic force that shapes our universe.
Reference: “Constraining Dark Energy from the Local Group Dynamics” by David Benisty, Anne-Christine Davis and N. Wyn Evans, 8 August 2023, The Astrophysical Journal Letters.
DOI: 10.3847/2041-8213/ace90b