Definitions of Nova, Black hole,Radio Galaxy, Redshirt, etc.

Nova - A star increases its brightness repentivamente and unprecedented ways, giving the impression that a new star has appeared where before there was nothing. Hence the name "nova" or again.

Black hole - An object whose gravity is so strong that not even light can escape it. Black holes represent the last stage of evolution of massive stars (from 10 to 15 times the mass of the sun). If a massive star goes supernova, the remains of the star, after the violent explosion, is a dead star that has run out of fuel. With no contrarrestren forces to gravity, this dead star will collapse on itself, to thus become a point of zero volume and infinite density, creating what is known as a "singularity". As the density increases, the trajectory of the light rays emitted by the star are bent until eventually surround the star. Any emitted photon is trapped in orbit by the intense gravitational field. Because light cannot escape once the star reaches infinite density, this object is called a black hole.

Redshirt - This is a shift of spectral lines towards larger wavelengths (or lower energies), and is the result of the remoteness of the object relative to the observer. The cosmological redshirt is the result of the expanding universe and the finite speed of light.

Dust disks of second generation - is a flattened disk of dust surrounding rotating stars during the period of planet formation. In a previous phase, in these protoplanetary disks are mixed dust and gas.

Non-Thermal Emission - In the thermal emission (black body) there is a clear relationship between the distribution of energy in wavelength and temperature of the object. By contrast, non-thermal radiation does not obey the relationship so simple. The synchrotron radiation in radio waves, emitted by electrons moving at relativistic velocities by a spiral around magnetic fields, is an example of non-thermal radiation.

Brown Dwarf - is an object of low luminosity with a mass that lies between a star and a planet. With a mass of between 1 and 8% of the Sun, a brown dwarf is too small for it to occur in thermonuclear fusion, which is what defines a star. Only a theoretical concept until 1995, hundreds of these objects has been discovered in recent years.

Ultra-luminous infrared galaxy (ULIRG) - This is ultra luminous infrared galaxies that emit most of their light in the infrared and have a brightness of over a billion suns. The high luminosity of ULIRGs is thought to be due to multiple events of star formation very widespread throughout the galaxy (perhaps caused by a collision between galaxies), or to an active galactic nucleus in the center of the galaxy. These objects were discovered by IRAS in 1983.

Radio Galaxy - A galaxy is extremely bright in radio waves. It is usually a giant elliptical galaxy intense source of synchrotron radiation.

Seyfert galaxy - A type of spiral galaxy whose nucleus is very bright and its spectrum shows broad emission lines.

Gravitational lens - can be a massive galaxy or galaxy cluster that lies between us and a distant astronomical object. His presence makes light of the object to deviate under the gravitational field of the lens. Gravitational lenses can focus, distort and divide the light beams in the same way that an ordinary lens.

Interstellar Medium (ISM)   -  Gas and dust found between stars of a galaxy.

Metallicity - is a measure of the amount of heavy elements (metals) containing the stars and the interstellar medium? In the astronomical context, a metal atom is any heavier than helium. Metals are the result of thermonuclear fusion of hydrogen and helium in stars, and during the later stages of stellar evolution these metals are ejected into the interstellar medium. The interstellar medium is therefore continually enriched by heavier elements novae and supernovae that occur in successive generations of stars.

Planetary Nebula - A bubble of gas surrounding a hot star dying. The star is so hot it makes the planetary nebula glow, allowing astronomers to see it. The star, who once was the core of a red giant, its outer atmosphere expelled creating a planetary nebula, which incidentally has nothing to do with planets, but through a small telescope its presence seems to remember the disk of a planet, and hence the misnomer.

Active Galactic Nuclei (AGN) - Active galactic nuclei (AGN) are the center of some galaxies where black holes are thought responsible for its luminosity. These nuclei produce enormous amounts of energy, exceeding the light emitted by all stars in the galaxy. A quasar is a specific type of AGN.

Quasar - Also known as quasi-stellar object (QSO). This is a star like object that has a large red shift and is a very strong source of radio waves. Most likely this is an extragalactic object (external to our Galaxy) highly luminous.

HII region - Nebula containing gaseous material to a temperature of about 10,000 degrees Kelvin. At this temperature the hydrogen is ionized and electrons move freely.

Supernova - A gigantic stellar explosion in which the star's luminosity increases billion times. Most of the star is scattered by the interstellar measured, leaving behind at least sometimes, extremandamente dense core may be a neutron star.

Super-Planet - A planet with a mass similar to Jupiter or larger. Jupiter is about 318 times more massive than Earth.

Astronomical Unit (AU) - The average distance between the Sun and Earth. 1 AU is 149,597,870.691 km (about 93 million miles). The Astronomical Unit is a constant that is used to measure distances within our solar system.

Young Universe - The Universe Young refers to approximately the first billion years after the Big Bang (Big Bang), estimated occurred about 14 billion years. Due to the expansion of the universe, this corresponds to the most distant reaches of the universe.