Nova

Nova+ was a Bulgarian reality TV channel. The channel launched with the start of the first season of Big Brother (Bulgaria) in 2004, which was also the first reality show in Bulgaria. During Big Brother 1 the name of the channel was simply Big Brother Live, but its name was changed into Nova+ after the start of the first season of Star Academy Bulgaria on 11 April 2005. The channel aired only during the Big Brother seasons from season 1 to 4. On 12 May 2008 Nova+ began airing full reality TV programme with popular reality formats. The channel was closed down on 31 December 2008, when Modern Times Group bought the Nova television and Diema groups from ANT1 Group and Balkan Media Group Limited.

hydrogen from the Roche lobe of its larger companion star A nova is a transient astronomical event that causes the sudden appearance of a bright, apparently "new" star (hence the name "nova", Latin for "new"; the shortened form of "stella nova", Latin for "new star") that slowly fades over weeks or months. All observed novae involve white dwarfs in close binary systems, but causes of the dramatic appearance of a nova vary, depending on the circumstances of the two progenitor stars. The main sub-classes of novae are classical novae, recurrent novae (RNe), and dwarf novae. They are all considered to be cataclysmic variable stars. Classical nova eruptions are the most common type. This type is usually created in a close binary star system consisting of a white dwarf and either a main sequence, subgiant, or red giant star. If the orbital period of the system is a few days or less, the white dwarf is close enough to its companion star to draw accreted matter onto its surface, creating a dense but shallow atmosphere. This atmosphere, mostly consisting of hydrogen, is heated by the hot white dwarf and eventually reaches a critical temperature, causing ignition of rapid runaway fusion. The sudden increase in energy expels the atmosphere into interstellar space, creating the envelope seen as visible light during the nova event. In past centuries such an event was thought to be a new star. A few novae produce short-lived nova remnants, lasting for perhaps several centuries. A recurrent nova involves the same processes as a classical nova, except that the nova event repeats in cycles of a few decades or less as the companion star again feeds the dense atmosphere of the white dwarf after each ignition, as in the star T Coronae Borealis. Under certain conditions, mass accretion can eventually trigger runaway fusion that destroys the white dwarf rather than merely expelling its atmosphere. In this case, the event is usually classified as a Type Ia supernova. Novae most often occur in the sky along the path of the Milky Way, especially near the observed Galactic Center in Sagittarius; however, they can appear anywhere in the sky. They occur far more frequently than galactic supernovae, averaging about ten per year in the Milky Way. Most are found telescopically, perhaps only one every 12–18 months reaching naked-eye visibility. Novae reaching first or second magnitude occur only a few times per century. The last bright nova was V1369 Centauri, which reached 3.3 magnitude on 14 December 2013. ==Remnants== : Nova of 1901 Some novae leave behind visible nebulosity, material expelled in the nova explosion or in multiple explosions.

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