Cosmology Archives

June 7, 2022June 7, 2022 by Laurence Tognetti

These Galaxies are Definitely Living in a Simulation

Studying the universe is hard. Really hard. Like insanely, ridiculously hard. Think of the hardest thing you’ve ever done in your life, because studying the universe is quite literally exponentially way harder than whatever you came up with. Studying the universe is hard for two reasons: space and time. When we look at an object in the night sky, we’re looking back in time, as it has taken a finite amount of time for the light from that object to reach your eyes. The star Sirius is one of the brightest objects in the night sky and is located approximately 8.6 light-years from Earth. This means that when you look at it, you’re seeing what it looked like 8.6 years ago, as the speed of light is finite at 186,000 miles per second and a light year is the time it takes for light to travel in one year. Now think of something way farther away than Sirius, like the Big Bang, which supposedly took place 13.8 billion years ago. This means when scientists study the Big Bang, they’re attempting to look back in time 13.8 billion years. Even with all our advanced scientific instruments, it’s extremely hard to look back that far in time. It’s so hard that the Hubble Space Telescope has been in space since 1990 and just recently spotted the most distant single star ever detected in outer space at 12.9 billion light-years away. That’s 30 years of scanning the heavens, which is a testament to the vastness of the universe, and hence why studying the universe is hard. Because studying the universe is so hard, scientists often turn to computer simulations, or models, to help speed up the science aspect and ultimately give us a better understanding of how the universe works without waiting 30 years for the next big discovery.

June 5, 2022June 5, 2022 by Brian Koberlein

Does a “Mirror World of Particles” Explain the Crisis in Cosmology?

Why create one universe when you could create two? Credit: NASA/WMAP Science Team, modified by Brian Koberlein

The idea of a mirror universe is a common trope in science fiction. A world similar to ours where we might find our evil doppelganger or a version of us who actually asked out our high school crush. But the concept of a mirror universe has been often studied in theoretical cosmology, and as a new study shows, it might help us solve problems with the cosmological constant.

April 8, 2022April 8, 2022 by Matt Williams

A New Record for the Most Distant Galaxy, Seen Just 300 Million Years After the Big Bang

Three-color image of HD1, the most distant galaxy candidate to date, created using data from the VISTA telescope. The red object in the center of the zoom-in image is HD1. Credit: Harikane et al.

Since the Renaissance astronomer Galileo Galilee first studied the heavens using a telescope he built himself, astronomers have been pushing the boundaries of what they can observe. After centuries of progress, they have been able to study and catalog objects in all but the earliest periods of the Universe. But thanks to next-generation instruments and technologies, astronomers will soon be able to observe the “Cosmic Dawn” era – ca. 50 million to billion years after the Big Bang.

In recent years, astronomers have made discoveries that preview what this will be like, the most recent of which is the galaxy candidate known as HD1. This galaxy is about 13.5 billion light-years from Earth (32.2 billion light-years in terms of “proper distance“), making it the farthest ever observed. This discovery implies that galaxies existed as early as 300 million years after the Big Bang, a finding which could have drastic implications for astronomy and cosmology!

March 31, 2022April 2, 2022 by Matt Williams

New Simulation Recreates an Early Time in the Universe That Still Hasn't Been Seen Directly

The fields of astronomy and astrophysics are poised for a revolution in the coming years. Thanks to next-generation observatories like the James Webb Space Telescope (JWST), scientists will finally be able to witness the formation of the first stars and galaxies in the Universe. In effect, they will be able to pierce the veil of the Cosmic Dark Ages, which lasted from roughly 370,000 years to 1 billion years after the Big Bang.

During this period, the Universe was filled with clouds of neutral hydrogen and decoupled photons that were not visible to astronomers. In anticipation of what astronomers will see, researchers from the Harvard & Smithsonian Center for Astrophysics (CfA), the Massachusetts Institute of Technology (MIT), and the Max Planck Institute for Astrophysics (MPIA) created a new simulation suite called Thesan that simulates the earliest period of galaxy formation.

March 25, 2022March 25, 2022 by Evan Gough

NASA’s Roman Mission Might Tell Us if the Universe Will Tear Itself Apart in the Future

The concept of accelerating expansion does get you wondering just how much it can accelerate. Theorists think there still might be a chance of a big crunch, a steady-as-she-goes expansion or a big rip. Or maybe just a little rip?

NASA’s Nancy Gracy Roman Space Telescope won’t launch until 2027, and it won’t start operating until some time after that. But that isn’t stopping excited scientists from dreaming about their new toy and all it will do. Who can blame them?

A new study examines the Roman Space Telescope’s power in detail to see if it can help us answer one of our most significant questions about the Universe. The question?

Will the Universe keep expanding and tear itself apart in a Big Rip?

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.

January 14, 2022January 14, 2022 by Evan Gough

Nancy Grace Roman Telescope Will do its Own, Wide-Angle Version of the Hubble Deep Field

This synthetic image visualizes what a Roman ultra-deep field could look like. The 18 squares at the top of this image outline the area Roman can see in a single observation, known as its footprint. The inset at the lower-right zooms into one of the squares of Roman's footprint, and the inset at the lower-left zooms in even further. The image, which contains more than 10 million galaxies, was constructed from a simulation that produced a realistic distribution of the galaxies in the universe. Image Credit: Nicole Drakos, Bruno Villasenor, Brant Robertson, Ryan Hausen, Mark Dickinson, Henry Ferguson, Steven Furlanetto, Jenny Greene, Piero Madau, Alice Shapley, Daniel Stark, Risa Wechsler

Remember the Hubble Space Telescope’s Deep Field and Ultra-Deep Field images?

Those images showed everyone that what appears to be a tiny, empty part of the sky contains thousands of galaxies, some dating back to the Universe’s early days. Each of those galaxies can have hundreds of billions of stars. These early galaxies formed only a few hundred million years after the Big Bang. The images inspired awe in the human minds that took the time to understand them. And they’re part of history now.

The upcoming Nancy Grace Roman Space Telescope (NGRST) will capture its own version of those historical images but in wide-angle. To whet our appetites for the NGRST’s image, a group of astrophysicists have created a simulation to show us what it’ll look like.

November 16, 2021November 16, 2021 by Matt Williams

A new Simulation of the Universe Contains 60 Trillion Particles, the Most Ever

Illustris simulation, showing the distribution of dark matter in 350 million by 300,000 light years. Galaxies are shown as high-density white dots (left) and as normal, baryonic matter (right). Credit: Markus Haider/Illustris

Today, the greatest mysteries facing astronomers and cosmologists are the roles gravitational attraction and cosmic expansion play in the evolution of the Universe. To resolve these mysteries, astronomers and cosmologists are taking a two-pronged approach. These consist of directly observing the cosmos to observe these forces at work while attempting to find theoretical resolutions for observed behaviors – such as Dark Matter and Dark Energy.

In between these two approaches, scientists model cosmic evolution with computer simulations to see if observations align with theoretical predictions. The latest of which is AbacusSummit, a simulation suite created by the Flatiron Institute’s Center for Computational Astrophysics (CCA) and the Harvard-Smithsonian Center for Astrophysics (CfA). Capable of processing nearly 60 trillion particles, this suite is the largest cosmological simulation ever produced.

November 12, 2021November 12, 2021 by Brian Koberlein

Understanding the Early Universe Depends on Estimating the Lifespan of Neutrons

How NASA's Lunar Prospector could study neutron decay. Credit: Johns Hopkins APL/Ben Smith

When we look into the night sky, we see the universe as it once was. We know that in the past the universe was once warmer and denser than it is now. When we look deep enough into the sky, we see the microwave remnant of the big bang known as the cosmic microwave background. That marks the limit of what we can see. It marks the extent of the observable universe from our vantage point.

November 2, 2021November 2, 2021 by Matt Williams

Is the Universe Fine-Tuned for Life?

For decades, various physicists have theorized that even the slightest changes in the fundamental laws of nature would make it impossible for life to exist. This idea, also known as the “Fine-Tuned Universe” argument, suggests that the occurrence of life in the Universe is very sensitive to the values of certain fundamental physics. Alter any of these values (as the logic goes), and life would not exist, meaning we must be very fortunate to be here!

But can this really be the case, or is it possible that life can emerge under different physical constants, and we just don’t know it? This question was recently tackled by Luke A. Barnes, a postdoctoral researcher at the Sidney Institute for Astronomy (SIA) in Australia. In his recent book, A Fortunate Universe: Life in a Finely Tuned Cosmos, he and Sydney astrophysics professor Geraint F. Lewis argued that a fine-tuned Universe makes sense from a physics standpoint.