Planetary nebulae, hidden white dwarfs. Supernova explosions that left as waste pulsars or black holes. The graveyards of stars.
The stars, after an evolution largely unchanged for much of his life, suffering spectacular processes that lead to death.
Planetary nebulae and white dwarfs. Dying Suns
The vast majority of stars, which have a mass similar to that of the Sun, end their lives transformed into ephemeral light sculptures and ionized gas, called planetary nebulae.
The planetary nebulae are presented in multiple and surprising variety of forms, gradually expanding, and with a maximum range that can reach more than a light year in diameter. In a period of about twenty to thirty thousand years of expansion will be finished by dispersing and mixing with the interstellar medium to disappear, leaving behind tiny stellar remnants called white dwarfs.
These structures are objects very “photogenic” to astronomers because, on one hand, most of the gas cloud is composed of hydrogen, while the central residue, the white dwarf, emitting ultraviolet radiation and ionized hydrogen atoms (makes ejected electrons). This creates a phenomenon of fluorescence in the cloud due to photon emission process visual ejected electrons to recombine.
The white dwarfs are initially very high surface temperatures, but are inert stars that have no nuclear reactions and shine for the issuance of stored energy while still active. They are also extremely dense stars, and from the core collapse by the force of gravity. A white dwarf with half the Sun’s mass is only 50% larger than Earth.
Slowly, the white dwarf will cool off and for which, for being so dense, it requires a time span of tens of thousands of millions of years. Finally be a dark size stellar corpse half a planet called black dwarf .
The death of a star is announced with a huge explosion called supernova, which releases to the environment surrounding most of its mass at a rate that can reach forty million miles per hour.
In the same way that planetary nebulae, supernovae leave behind a residue: a neutron star or black hole, leading the compression phase of the stellar core to unprecedented levels.
There are two types of supernova explosion: the types I and II. In the first case, the source are binary systems (two stars), very common in the universe, where a white dwarf draws material from its companion nearby. Stolen mass accumulates on the surface of the white dwarf until the effect of gravitational force, the star begins to contract. This contraction continues until the star cannot be more dense, when it expands suddenly generating a series of powerful shock waves that tear the star and what is perceived as a supernova. The original white dwarf is destroyed.