standard model of cosmology Archives

August 31, 2024August 31, 2024 by Mark Thompson

Estimating the Basic Settings of the Universe

This snapshot compares the distribution of galaxies in a simulated universe used to train SimBIG (right) to the galaxy distribution seen in the real universe (left). Bruno Régaldo-Saint Blancard/SimBIG collaboration

The Standard Model describes how the Universe has evolved at large scale. There are six numbers that define the model and a team of researchers have used them to build simulations of the Universe. The results of these simulations were then fed to a machine learning algorithm to train it before it was set the task of estimating five of the cosmological constants, a task which it completed with incredible precision.

August 29, 2024August 31, 2024 by Matt Williams

Remember those Impossible Galaxies Found by JWST? It Turns Out They Were Possible After All

This is a small portion of the field observed by NASA’s James Webb Space Telescope’s NIRCam (Near-Infrared Camera) for the Cosmic Evolution Early Release Science (CEERS) survey. It is filled with galaxies. The light from some of them has traveled for over 13 billion years to reach the telescope. Credit: NASA, ESA, CSA, Steve Finkelstein (University of Texas at Austin)

When the James Webb Space Telescope provided astronomers with a glimpse of the earliest galaxies in the Universe, there was some understandable confusion. Given that these galaxies existed during “Cosmic Dawn,” less than one billion years after the Big Bang, they seemed “impossibly large” for their age. According to the most widely accepted cosmological model—the Lambda Cold Dark Matter (LCDM) model—the first galaxies in the Universe did not have enough time to become so massive and should have been more modestly sized.

This presented astronomers with another “crisis in cosmology,” suggesting that the predominant model about the origins and evolution of the Universe was wrong. However, according to a new study by an international team of astronomers, these galaxies are not so “impossibly large” after all, and what we saw may have been the result of an optical illusion. In short, the presence of black holes in some of these early galaxies made them appear much brighter and larger than they actually were. This is good news for astronomers and cosmologists who like the LCDM the way it is!

January 13, 2024January 13, 2024 by Scott Alan Johnston

Two Giant Structures Have Been Found Billions of Light-Years Away

Artistic impression of the Giant Arc and the Big Ring on the sky. Background image credit: Stellarium.

The early universe, according to the Standard Model of Cosmology, ought to be a fairly homogenous place, with little structure or arrangement. In 2021, however, astronomers discovered a large pattern of galaxies forming a giant arc 3.3 billion light years across. Now, a second large-scale pattern has emerged. This time, it’s an enormous circle of galaxies, nicknamed the Big Ring. Together, the Giant Arc and the Big Ring present a challenge to the Standard Model, and may send cosmologists back to the drawing board.

October 5, 2023October 5, 2023 by Laurence Tognetti

The Big Bang: What is it? Why study it? What happened before? How will it all end?

Approximately 13.8 billion years ago, the greatest event in all of existence occurred that literally created existence itself. This event is known as the Big Bang, and it’s responsible for the estimated septillion number of stars that are scattered across the vast reaches of the unknown, including the one our small, blue world orbits. However, other than knowing that the Big Bang occurred, there is still a septillion amount of information we still don’t know about the greatest event in the history of existence.

April 19, 2023April 19, 2023 by Matt Williams

The First Light in the Universe Helps Build a Dark Matter Map

A view of Stephan’s Quintet, a visual grouping of five galaxies from the James Webb Telescope. Credit: NASA/ESA/CSA/STScI

In the 1960s, astronomers began noticing a pervasive microwave background visible in all directions. Thereafter known as the Cosmic Microwave Background (CMB), the existence of this relic radiation confirmed the Big Bang theory, which posits that all matter was condensed onto a single point of infinite density and extreme heat that began expanding ca. 13.8 years ago. By measuring the CMB for redshift and comparing these to local distance measurements (using variable stars and supernovae), astronomers have sought to measure the rate at which the Universe is expanding.

Around the same time, scientists observed that the rotational curves of galaxies were much higher than their visible mass suggested. This meant that either Einstein’s Theory of General Relativity was wrong or the Universe was filled with a mysterious, invisible mass. In a new series of papers, members of the Atacama Cosmology Telescope (ACT) collaboration have used background light from the CMB to create a new map of Dark Matter distribution that covers a quarter of the sky and extends deep into the cosmos. This map confirms General Relativity and its predictions for how mass alters the curvature of spacetime.

February 17, 2023February 17, 2023 by Matt Williams

Are Black Holes the Source of Dark Energy?

An illustration of cosmic expansion. Credit: NASA's Goddard Space Flight Center Conceptual Image Lab

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.

February 23, 2022February 23, 2022 by Matt Williams

A Detailed Simulation of the Universe Creates Structures Very Similar to the Milky Way and its Surroundings

Simulation of dark matter and gas. Credit: Illustris Collaboration (CC BY-SA 4.0)

In their pursuit of understanding cosmic evolution, scientists rely on a two-pronged approach. Using advanced instruments, astronomical surveys attempt to look farther and farther into space (and back in time) to study the earliest periods of the Universe. At the same time, scientists create simulations that attempt to model how the Universe has evolved based on our understanding of physics. When the two match, astrophysicists and cosmologists know they are on the right track!

In recent years, increasingly-detailed simulations have been made using increasingly sophisticated supercomputers, which have yielded increasingly accurate results. Recently, an international team of researchers led by the University of Helsinki conducted the most accurate simulations to date. Known as SIBELIUS-DARK, these simulations accurately predicted the evolution of our corner of the cosmos from the Big Bang to the present day.

June 15, 2020June 15, 2020 by Brian Koberlein

Evidence is Building that the Standard Model of the Expansion of the Universe Needs some new Ideas

Artist's conception illustrating a disk of water-bearing gas orbiting the supermassive black hole at the core of a distant galaxy. Credit: Sophia Dagnello, NRAO/AUI/NSF

Once again a new measurement of cosmic expansion is encouraging astronomers to reconsider the standard cosmological model. The problem is the Hubble constant and dark energy. While we have a broad understanding of dark energy, pinning down the value of the Hubble constant has been a problem, since different measurements keep getting different results. Now a new study has been published which further complicates things.

March 1, 2020March 1, 2020 by Matt Williams

What is the Steady State Hypothesis?

Artist's impression of the Milky Way Galaxy. Credit: ESO

When it comes to our cosmic origins, a number of theories have been advanced throughout the course of history. Literally every culture that’s ever existed has had its own mythological tradition, which naturally included a creation story. With the birth of the scientific tradition, scientists began to understand the Universe in terms of physical laws that could be tested and proven.

With the dawn of the Space Age, scientists began testing cosmological theories in terms of observable phenomena. From all of this, a number of theories emerged by the latter half of the 20th century that attempted to explain how all matter and the physical laws governing it came to be. Of these, the Big Bang Theory remains the most widely accepted while the Steady-State Hypothesis has historically been its greatest challenger.

June 10, 2019January 26, 2022 by Matt Williams

New observations from the Planck mission don’t resolve anomalies like the CMB “cold spot”

Cosmic Microwave Background. Scientists compared this to modern galaxy distributions to track dark matter. Copyright: ESA/Planck Collaboration

Back in 2013, the European Space Agency released its first analysis of the data gathered by the Planck observatory. Between 2009 and 2013, this spacecraft observed the remnants of the radiation that filled the Universe immediately after the Big Bang – the Cosmic Microwave Background (CMB) – with the highest sensitivity of any mission to date and in multiple wavelengths.

In addition to largely confirming current theories on how the Universe evolved, Planck’s first map also revealed a number of temperature anomalies – like the CMB “Cold Spot” – that are difficult to explain. Unfortunately, with the latest analysis of the mission data, the Planck Collaboration team has found no new evidence for these anomalies, which means that astrophysicists are still short of an explanation.