Galaxies are made of stars, dust and dark matter, all held together by gravity. They come in a variety of shapes, sizes and ages, and many have black holes at their centers.Know More
Galaxies contain a different number of planets, star systems, star clusters and types of interstellar clouds. In between them is a sparse interstellar medium of gas, dust and cosmic rays. The black holes at the center of most galaxies are considered to be the primary driver of active galactic nuclei found at the core, and their surroundings produce enormous amounts of energy that astronomers can see over great distances. Material surrounding the black hole is accelerated outwards by its jets. Other galaxies contain objects like quasars, the most energetic bodies in the universe, at their cores.
Galaxies are categorized according to their apparent shape, referred to as their visual morphology. A common form is the elliptical galaxy which has an ellipse-shaped light profile. Spiral galaxies are disk-shaped with dusty, curving arms, and those with irregular shapes are known as irregular galaxies and typically originate from disruption by the gravitational pull of neighboring galaxies. Interactions between neighboring galaxies, which can result in a merger, sometimes induce significantly increased incidents of star formation leading to starburst galaxies.Learn more about Stellar Astronomy
Stars are big balls of gas, and they shine because the gas inside is so hot that it causes nuclear fusion, which is the energy releasing process that people can see from earth. Nuclear fusion is where two individual atoms fuse and form a different atom.Full Answer >
The two types of stars that end with supernovae are white dwarfs and massive stars that are at least eight times the mass of the sun. Each of these types of stars undergoes a thermonuclear reaction at the end of its life.Full Answer >
The stars appear to move from east to west across the night sky because as Earth rotates, the sky is observed as rotating, according to Astronomy Education at the University of Nebraska–Lincoln. Observers on Earth, in both the northern and southern hemispheres, see objects in the sky move counter-clockwise.Full Answer >
Most stars cannot be seen during daylight hours because light from the sun is brighter than the relatively faint light from the other stars. This is largely a result of the Earth's atmosphere scattering the sun's light so that every point in the sky seems brighter than distant stars.Full Answer >