What contains a petabyte of data on more than a billion galaxies in one of the most extensive sky maps? The answer: the ever-expanding Dark Energy Spectroscopic Instrument (DESI) Legacy Imaging Survey. The galaxies it charts are part of the largest two-dimensional map of the sky ever made. And, just recently, it grew even larger with the addition of new data from telescopes in the U.S. and Chile.Continue reading “A New Survey of the Sky Contains Over One Billion Galaxies”
Are Black Holes the Source of Dark Energy?
By the 1920s, astronomers learned that the Universe was expanding as Einstein’s Theory of General Relativity predicted. This led to a debate among astrophysicists between those who believed the Universe began with a Big Bang and those who believed the Universe existed in a Steady State. By the 1960s, the first measurements of the Cosmic Microwave Background (CMB) indicated that the former was the most likely scenario. And by the 1990s, the Hubble Deep Fields provided the deepest images of the Universe ever taken, revealing galaxies as they appeared just a few hundred million years after the Big Bang.
Over time, these discoveries led to an astounding realization: the rate at which the Universe is expanding (aka. the Hubble Constant) has not been constant over time! This led to the theory of Dark Energy, an invisible force that counteracts gravity and causes this expansion to accelerate. In a series of papers, an international team of researchers led by the University of Hawaii reported that black holes in ancient and dormant galaxies were growing more than expected. This constitutes (they claim) the first evidence that black holes could be the source of Dark Energy.Continue reading “Are Black Holes the Source of Dark Energy?”
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Could a Dark Energy Phase Change Relieve the Hubble Tension?
According to the most widely-accepted cosmological theories, the Universe began roughly 13.8 billion years ago in a massive explosion known as the Big Bang. Ever since then, the Universe has been in a constant state of expansion, what astrophysicists know as the Hubble Constant. For decades, astronomers have attempted to measure the rate of expansion, which has traditionally been done in two ways. One consists of measuring expansion locally using variable stars and supernovae, while the other involves cosmological models and redshift measurements of the Cosmic Microwave Background (CMB).
Unfortunately, these two methods have produced different values over the past decade, giving rise to what is known as the Hubble Tension. To resolve this discrepancy, astronomers believe that some additional force (like “Early Dark Energy“) may have been present during the early Universe that we haven’t accounted for yet. According to a team of particle physicists, the Hubble Tension could be resolved by a “New Early Dark Energy” (NEDE) in the early Universe. This energy, they argue, would have experienced a phase transition as the Universe began to expand, then disappeared.Continue reading “Could a Dark Energy Phase Change Relieve the Hubble Tension?”
“Early Dark Energy” Could Explain the Crisis in Cosmology
In 1916, Einstein finished his Theory of General Relativity, which describes how gravitational forces alter the curvature of spacetime. Among other things, this theory predicted that the Universe is expanding, which was confirmed by the observations of Edwin Hubble in 1929. Since then, astronomers have looked farther into space (and hence, back in time) to measure how fast the Universe is expanding – aka. the Hubble Constant. These measurements have become increasingly accurate thanks to the discovery of the Cosmic Microwave Background (CMB) and observatories like the Hubble Space Telescope.
Astronomers have traditionally done this in two ways: directly measuring it locally (using variable stars and supernovae) and indirectly based on redshift measurements of the CMB and cosmological models. Unfortunately, these two methods have produced different values over the past decade. As a result, astronomers have been looking for a possible solution to this problem, known as the “Hubble Tension.” According to a new paper by a team of astrophysicists, the existence of “Early Dark Energy” may be the solution cosmologists have been looking for.Continue reading ““Early Dark Energy” Could Explain the Crisis in Cosmology”
Einstein's Predictions for Gravity Have Been Tested at the Largest Possible Scale
According to the Standard Model of Particle Physics, the Universe is governed by four fundamental forces: electromagnetism, the weak nuclear force, the strong nuclear force, and gravity. Whereas the first three are described by Quantum Mechanics, gravity is described by Einstein’s Theory of General Relativity. Surprisingly, gravity is the one that presents the biggest challenges to physicists. While the theory accurately describes how gravity works for planets, stars, galaxies, and clusters, it does not apply perfectly at all scales.
While General Relativity has been validated repeatedly over the past century (starting with the Eddington Eclipse Experiment in 1919), gaps still appear when scientists try to apply it at the quantum scale and to the Universe as a whole. According to a new study led by Simon Fraser University, an international team of researchers tested General Relativity on the largest of scales and concluded that it might need a tweak or two. This method could help scientists to resolve some of the biggest mysteries facing astrophysicists and cosmologists today.Continue reading “Einstein's Predictions for Gravity Have Been Tested at the Largest Possible Scale”
The Dark Energy Camera has Captured a Million Images, an Eighth of the Entire sky. Here are Some of its Best Pictures so far
In August 2013, the Dark Energy Survey (DES) began its six-year mission to map thousands of galaxies, supernovae, and patterns in the cosmic structure. This international collaborative effort is dedicated to investigating the mysterious phenomenon known as Dark Energy. This theoretical force counter-acts gravity and accounts for 70% of the Universe’s energy-mass density. Their primary instrument in this mission is the 570-megapixel Dark Energy Camera (DECam), mounted on the Victor M. Blanco 5-meter (16.4 ft) telescope at the Cerro Tlelolo Inter-American Observatory in Chile.
Between 2013 and 2019, the DECam took over one million exposures of the southern night sky and photographed around 2.5 billion astronomical objects – including galaxies, galaxy clusters, stars, comets, asteroids, dwarf planets, and supernovae. For our viewing pleasure, the Dark Energy Survey recently released fifteen spectacular images taken by the DECam during the six-year campaign. These images showcase the capabilities of the DECam, the types of objects it observed, and the sheer beauty of the Universe!Continue reading “The Dark Energy Camera has Captured a Million Images, an Eighth of the Entire sky. Here are Some of its Best Pictures so far”
On its Hunt for Dark Energy, a Telescope Stopped to Look at the Lobster Nebula
If you thought dark matter was difficult to study, studying dark energy is even more challenging. Dark energy is perhaps the most subtle phenomenon in the universe. It drives the evolution of the cosmos, but its effects are only seen on intergalactic scales. So to study dark energy in detail, you need a great deal of observations of wide areas of the sky.Continue reading “On its Hunt for Dark Energy, a Telescope Stopped to Look at the Lobster Nebula”
A New Study Confirms That Gravity has Remained Constant for the Entire age of the Universe
For over a century, astronomers have known that the Universe has been expanding since the Big Bang. For the first eight billion years, the expansion rate was relatively consistent since it was held back by the force of gravitation. However, thanks to missions like the Hubble Space Telescope, astronomers have since learned that roughly five billion years ago, the rate of expansion has been accelerating. This led to the widely-accepted theory that a mysterious force is behind the expansion (known as Dark Energy), while some insist that the force of gravity may have changed over time.
This is a contentious hypothesis since it means that Einstein’s General Theory of Relativity (which has been validated nine ways from Sunday) is wrong. But according to a new study by the international Dark Energy Survey (DES) Collaboration, the nature of gravity has remained the same throughout the entire history of the Universe. These findings come shortly before two next-generation space telescopes (Nancy Grace Roman and Euclid) are sent to space to conduct even more precise measurements of gravity and its role in cosmic evolution.Continue reading “A New Study Confirms That Gravity has Remained Constant for the Entire age of the Universe”
Neutron Stars Could be the Best way to Measure Dark Energy
Dark energy is central to our modern theory of cosmology. We know the universe is expanding at an ever-increasing rate, and the clearest explanation is that some kind of energy is driving it. Since this energy doesn’t emit light, we call it dark energy. But simply giving dark energy a name doesn’t mean we fully understand it. We can see what dark energy does, but its fundamental nature is perhaps the biggest scientific mystery we have.Continue reading “Neutron Stars Could be the Best way to Measure Dark Energy”
Finally, an Explanation for the Cold Spot in the Cosmic Microwave Background
According to our current Cosmological models, the Universe began with a Big Bang roughly 13.8 billion years ago. During the earliest periods, the Universe was permeated by an opaque cloud of hot plasma, preventing atoms from forming. About 380,000 years later, the Universe began to cool and much of the energy generated by the Big Bang converted into light. This afterglow is now visible to astronomers as the Cosmic Microwave Background (CMB), first observed during the 1960s.
One peculiar characteristic about the CMB that attracted a lot of attention was the tiny fluctuations in temperature, which could provide information about the early Universe. In particular, there is a rather large spot in the CMB that is cooler than the surrounding afterglow, known as the CMB Cold Spot. After decades of studying the CMB’s temperature fluctuations, a team of scientists recently confirmed the existence of the largest cold spots in the CMB afterglow – the Eridanus Supervoid – might be the explanation for the CMB Cold Spot that astronomers have been looking for!Continue reading “Finally, an Explanation for the Cold Spot in the Cosmic Microwave Background”