EMISSION NEBULA
An emission nebula is a nebula formed of ionized gases that emit light of various wavelengths.The most common source of ionization is high-energy ultraviolet photons emitted from a nearby hot star.
REFLECTION NEBULA
A reflection nebula is a nebula that shines by reflecting the light of nearby stars.The energy from the nearby stars is insufficient to ionize the gas of the nebula to create an emission nebula.
PLANETORY NEBULA
A planetary nebula is a shell of ionized gas ejected from a red giant star.It is a type of emission nebula consisting of an expanding, glowing shell of ionized gas ejected from red giant stars late in their lives.
SUPERNOVA NEBULA
A supernova nebula is a remnant of a supernova explosion, containing gas and dust expelled from the explosion.The supernova remnant is bounded by an expanding shock wave.
DARK NEBULA
A dark nebula is a dense region of gas and dust that blocks light from objects behind it.Clusters and large complexes of dark nebulae are associated with Giant Molecular Clouds.
FLUX NEBULA
Flux nebulae are a relatively recently identified astronomical phenomenon. In contrast to the typical and well known gaseous nebulae within the plane of the Milky Way galaxy.
STARS
A star is a luminous spheroid of plasma held together by self-gravity.The nearest star to Earth is the Sun. Many other stars are visible to the naked eye at night; their immense distances from Earth make them appear as fixed points of light. The most prominent stars have been categorised into constellations and asterisms, and many of the brightest stars have proper names. Astronomers have assembled star catalogues that identify the known stars and provide standardized stellar designations. The observable universe contains an estimated 1022 to 1024 stars. Only about 4,000 of these stars are visible to the naked eye all within the Milky Way galaxy.
A star's life begins with the gravitational collapse of a gaseous nebula of material largely comprising hydrogen, helium, and trace heavier elements. Its total mass mainly determines its evolution and eventual fate. A star shines for most of its active life due to the thermonuclear fusion of hydrogen into helium in its core.
Stars can form orbital systems with other astronomical objects, as in planetary systems and star systems with two or more stars. When two such stars orbit closely, their gravitational interaction can significantly impact their evolution. Stars can form part of a much larger gravitationally bound structure, such as a star cluster or a galaxy.