Cosmology Archives - Page 3 of 16

October 8, 2020October 8, 2020

Gravitational-Wave Lensing is Possible, but it’s Going to be Incredibly Difficult to Detect

Gravity is a strange thing. In our everyday lives, we think of it as a force. It pulls us to the Earth and holds planets in orbits around their stars. But gravity isn’t a force. It is a warping of space and time that bends the trajectory of objects. Throw a ball in deep space, and it moves in a straight line following Newton’s First Law of Motion. Throw the same ball near the Earth’s surface, and it follows a parabolic trajectory caused by Earth’s warping of spacetime around it.

September 17, 2020September 17, 2020

Colliding Neutron Stars Don’t Make Enough Gold to Explain What We See in the Universe

In the beginning, the universe created three elements: hydrogen, helium, and lithium. There isn’t much you can do with these simple elements, other than to let gravity collapse them into stars, galaxies, and black holes. But stars have the power of alchemy. Within their hearts, they can fuse these elements into new ones. Carbon, nitrogen, oxygen, and others, all up to the heavy element of iron. When these first stars exploded, they scattered the new elements across the cosmos, creating planets, new stars, and even us.

September 5, 2020September 5, 2020

New Simulation Shows Exactly What Dark Matter Would Look Like If We Could See It

How do you study something invisible? This is a challenge that faces astronomers who study dark matter. Although dark matter comprises 85% of all matter in the universe, it doesn’t interact with light. It can only be seen through the gravitational influence it has on light and other matter. To make matters worse, efforts to directly detect dark matter on Earth have been unsuccessful so far.

August 17, 2020August 17, 2020

The Last Supernovae

A supernova is a powerful event. For a brief moment in time, a star shines as bright as a galaxy, ripping itself apart in a last, desperate attempt to fight against its gravity. While we see supernovae as rare and wondrous things, they are quite common. Based on observations of isotopes in our galaxy, we know that about twenty supernovae occur in the Milky Way every thousand years. These brilliant cosmic flashes fill the universe with heavy elements, and their remnant dust makes up almost everything we see around us. But supernovae won’t keep happening forever. At some point in the far future, the universe will see the last supernova.

July 20, 2020July 20, 2020

What Shuts Down a Galaxy’s Star Formation?

In the 1920s, Edwin Hubble studied hundreds of galaxies. He found that they tended to fall into a few broad types. Some contained elegant spirals of bright stars, while others were spherical or elliptical with little or no internal structure. In 1926 he developed a classification scheme for galaxies, now known as Hubble’s Tuning Fork.

Hubble’s tuning fork diagram for galaxies. Credit: Edwin Hubble

When you look at Hubble’s scheme, it suggests an evolution of galaxies, beginning as an elliptical galaxy, then flattening and shifting into a spiral galaxy. While many saw this as a reasonable model, Hubble cautioned against jumping to conclusions. We now know ellipticals do not evolve into spirals, and the evolution of galaxies is complex. But Hubble’s scheme marks the beginning of the attempt to understand how galaxies grow, live, and die.

June 6, 2020June 6, 2020

A New Telescope is Ready to Start Searching for Answers to Explain Dark Energy

Back in 2015, construction began on a new telescope called the Dark Energy Spectroscopic Instrument (DESI). Later this year, it will begin its five-year mission. Its goal? To create a 3D map of the Universe with unprecedented detail, showing the distribution of matter.

That detailed map will allow astronomers to investigate important aspects of cosmology, including dark energy and its role in the expansion of the Universe.

May 7, 2020May 7, 2020

In the far future, the universe will be mostly invisible

If you look out on the sky on a nice clear dark night, you’ll see thousands of intense points of light. Those stars are incredibly far away, but bright enough to be seen with the naked eye from that great distance – a considerable feat. But what you don’t see are all the small stars, the red dwarfs, too small and dim to be seen at those same distances.

March 1, 2020March 1, 2020

What is the Steady State Hypothesis?

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.

February 13, 2020February 13, 2020

Astronomers Simulated How the Universe Would Look Without Dark Matter

Since the 1960s, there has been a general consensus among astronomers and cosmologists that the majority of the Universe is made up of an invisible, mysterious mass (known as Dark Matter). While scientists still haven’t identified the candidate particle that makes up this mass, indirect tests and simulations have shown that Dark Matter must exist in order for the Universe to be the way it is.

In a fascinating twist, a team of European researchers conducted a simulation that looked at a Universe without Dark Matter. Using an alternative theory known as MOdified Newtonian Dynamics (MOND), the team created a computer simulation in which the galaxies were actually very similar to what we see in the Universe today. These findings could help to resolve one of the most enduring mysteries of modern cosmology.

November 6, 2019November 6, 2019

New Research Suggests that the Universe is a Sphere and Not Flat After All

The universe is a seemingly endless sea filled with stars, galaxies, and nebulae. In it, we see patterns and constellations that have inspired stories throughout history. But there is one cosmic pattern we still don’t understand. A question that remains unanswered: What is the shape of the universe? We thought we knew, but new research suggests otherwise, and it could point to a crisis in cosmology.