|Update Dec. 27: Nova Centauri 2013 peaked at about magnitude 3.6 on December 5th, faded to 4.3 by the 9th, rebrightened to 3.5 around the 15th, and has been behaving oddly since. As of December 27th it's still naked-eye at magnitude 4.4. See preliminary light curve from the AAVSO.|
By 6:37 UT on the 4th, Sebastian Otero in Argentina found it to be magnitude 4.3. That's a trace brighter than the much-followed Nova Delphini 2013 at its peak last August. Here's the new nova's current AAVSO light curve.
Will it brighten further? If you’re in the Southern Hemisphere, go out and look! The nova is in the south-southeast before your local start of morning twilight, at right ascension 13h 54m 45s, declination —59° 09.1′. It's at the location of a previously 15th-magnitude star, possibly the progenitor.
Its preliminary designation was PNV J13544700-5909080. Now it's Nova Centauri 2013. Here’s a 10°-wide comparison-star chart from the AAVSO. The nova is centered on the chart, and the bright star is Beta Cen.
A nova happens in a special kind of tightly-orbiting binary star system: one where a relatively normal star pours a stream of hydrogen onto the surface of a companion white dwarf. When the layer of fresh hydrogen on the white dwarf's surface grows thick and dense enough, the bottom of the layer explodes in a runaway hydrogen-fusion reaction — a hydrogen bomb in the shape of a thin shell around the star. The underlying white dwarf remains intact, and as new hydrogen builds up, the process may repeat in a few years to tens of thousands of years.