Since the 20th century there have been two main types of astronomy, observational and theoretical astronomy. Observational astronomy uses telescopes and cameras to observe or look at stars, galaxies and other astronomical objects.

13.8 billion years

Definition of astronomy: Astronomy is the study of the sun, moon, stars, planets, comets, gas, galaxies, gas, dust and other non-Earthly bodies and phenomena. However, modern astronomy includes many elements of the motions and characteristics of these bodies, and the two terms are often used interchangeably today.

For the new century, astronomers’ long-term goal is to assemble a detailed picture of the formation, evolution, and destiny of the universe, and of its constituent galaxies, stars, and planets, which include the Milky Way, the Sun, and Earth.

Astronomy is the branch of science that studies the universe, the stars and the planets. Astronomy combines aspects of maths and physics to study how the universe was formed and the celestial bodies that are contained within it. It is the oldest of the natural sciences.

Dark matter, a component of the universe whose presence is discerned from its gravitational attraction rather than its luminosity. Dark matter makes up 30.1 percent of the matter-energy composition of the universe; the rest is dark energy (69.4 percent) and “ordinary” visible matter (0.5 percent).

Scientists believe that dark matter in the cluster accounts for the unexplained mass. More recently, astronomers have used NASA’s Chandra X-ray Observatory to make the most detaile measurement yet of the distribution of dark matter in a massive cluster of galaxies.

For decades, physicists have hypothesized that weakly interacting massive particles (WIMPs) are the strongest candidate for dark matter — the mysterious substance that makes up 85% of the Universe’s mass.

This can only be true, given the wide variety of colliding clusters where this has been demonstrated, if some new form of mass obeys different collisional laws than normal matter does. The inescapable conclusion is that some new form of matter — dark matter — must make up the majority of the Universe’s mass.

Dark matter is an invisible form of matter that makes up the bulk of the universe’s mass and creates the scaffolding upon which galaxies are built. Although astronomers cannot see dark matter, they can detect its presence indirectly by measuring how its gravity affects stars and galaxies.

The familiar material of the universe, known as baryonic matter, is composed of protons, neutrons and electrons. Dark matter may be made of baryonic or non-baryonic matter. To hold the elements of the universe together, dark matter must make up approximately 80% percent of the universe.