All the atoms in the universe together with light make up less than five percent of the total content of the universe. The rest are made up of dark matter and dark energy, which are invisible but dominate the structure and evolution of the universe.

Dark matter forms the vast majority of galaxies and galaxies, and is responsible for the large-scale arrangement of galaxies. Meanwhile, dark energy is the name we give to the mysterious influence that leads to the rapid expansion of the universe. What these materials are and how they work are some of the major challenges facing modern astronomers.

Our work

Astronomy Center | Harvard & Smithsonian scientists study dark matter and dark energy in several ways:

• Observation to measure the effects of dark matter on the structure and evolution of galaxies. The next generation giant Magellan telescope (GMT) will provide new information about large galaxies and detect dwarf galaxies that cannot be seen using current instruments. This type of study is important because dark matter models predict more dwarf galaxies than we observe.
• Creating theoretical models of dark material behavior from observational data. Since we do not have direct measurements of the behavior of dark matter, researchers must guess what particles look like from indirect sources.
• Measuring cosmic acceleration by mapping the position of tens of thousands of galaxies. The Barion Oscillation Spectroscopic Survey (BOSS) is an astronomical program that provides some excellent observational data on dark energy.

Invisible glue

The dark thing is not simply dark: it is invisible. All kinds of light pass through as if they were completely transparent. However, dark matter has mass, as we see by its gravitational influence.

Studies of galaxies show that stars and gases are moving, but they are far more than just pulling. Based on the motion we can observe, the galaxy theme is in a "halo" around the natural object of the galaxy.

Astronomers also study dwarf galaxies, which are less bright and therefore harder to observe, but have a larger area of ​​dark matter than their larger relatives.

Galaxies can contain hundreds or thousands of galaxies, each with its own halo of dark matter. However, the cluster has its own dark matter, which brings it all together.

This dark matter affects individual galaxies and how hot gas moves into the cluster. Astronomers, such as galaxies, can measure the amount of invisible mass within a cluster by the motion of a visible object. Researchers can determine the amount of dark matter in a cluster by how much gravity affects light. This effect is called gravitational lensing, and it provides an independent measure of how much mass is in a cluster and where it is located.

A particular galaxy, called the Bullet Cluster, provides some excellent evidence for the existence of dark matter. This cluster was made up of two small clusters that collided in the past. During this collision, hot gas is involved to create the shock wave generated by the bullet.

However, gravitational lensing shows that most concentrated clusters accumulate around galaxies rather than at the center of the gas. It provides the first independent measurement of how much gas and dark matter is present in a galaxy cluster, where plasma and black matter occupy the same part of most clusters.

Using fluctuations in the cosmic microwave background (CMP), astronomers determined that dark matter is about 27% of the universe's content, based on its total contribution to the total mass and energy content of the universe.

Faster and faster

In the 1920s, astronomers, including Edwin Hubble, discovered that galaxies seemed to be moving away from us, and that the farther away they were, the faster they retreated. In conjunction with Einstein's general theory of relativity, the researchers concluded that the universe expands and carries galaxies with it.

Then in 1998, two independent research groups announced that they were measuring cosmic expansion with greater accuracy, and found that it was accelerating. This acceleration refers to some unknown force that resists the force of gravity to expand the universe at a greater rate.

We call that mysterious force the "black force." Despite the name, dark energy is not the same as dark matter, they are both invisible. Dark matter pulls galaxies together, while dark energy pushes them away.

Astronomers measure the expansion of the universe using white dwarf explosions known as the Ia supernova, which led to the discovery of dark energy in 1998.They use thousands of galaxies to map out sound waves called boron sound waves (BAOs) created when the universe was young, which expands as the universe expands. In addition, CMB measurements show that dark energy contributes 68% of the total energy content of the universe.