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.
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
Strictly, black holes don't actually lead anywhere, as they are not holes in the common sense of the term. According to the Harvard Smithsonian Center for Astrophysics, black holes are regions of the universe in which matter has become so dense that nothing, not even light, can escape its gravitational pull. Within this volume, the original matter has become so compact that it can fairly be said to have disappeared.Full Answer >
Interstellar bubbles are made when stellar winds caused by massive stars or supernovae push the interstellar gas around them outwards in a bubble shape. Stars clustered close enough together form giant bubbles when their bubbles merge. These giant bubbles are known as superbubbles.Full Answer >
Stars do die. The nuclear fusion reaction in stars stops and the star shrinks into a white dwarf due to gravity. The white dwarf further shrinks by releasing energy and becomes a black dwarf, when no energy is released either by fusion or by shrinking.Full Answer >
Star type M, the red stars, are the coolest stars with an average surface temperature of under 3,500 K. This type of star has a 0.3 solar mass (M☉) and an average radius of 0.4 solar radius (R☉). Examples of red stars are Betelgeuse and Antares.Full Answer >