In 2001 a nova emerged in the constellation Puppis. V445 Puppis as it was called, increased 250x in brightnedd. It has been discussed ever since, wheter it is a beginning class Ia supernova or "just" a variable star-nova

V445 is in fact not a single star, but a close binary-system, consisting of an A0V star and a white dwarf-sta. While the white dwarf accretes matter from the larger star, it varies slightly in brightnessover a period of approximatly 16hours

The system has been studied in great details since the outburst, allowing the astronomers to watch, as a small nebula of dust and gasses expanded from V445

The images show a bipolar shell, initially with a very narrow waist, with lobes on each side. Two knots are also seen at both the extreme ends of the shell, which appear to move at about 30 million km/h. The shell - unlike any previously observed for a nova - is itself moving at about 24 million km/h. A thick disc of dust, which must have been produced during the last outburst, obscures the two central stars

However; the peculiar thing about the outburst itself was the lack of Hydrogen in its spectrum. Instead it contained strong emission lines of carbon, oxygen, calcium, sodium, and iron. This spectrum resembles a class 1a supernova, which is produced by a white dwarf accreting matter untill it reaches the critical Chandrasekhar limit  of 1,38 solar masses.

However a newly published article on arXiv argues against the hypothesis, that the V445 outburst could be a predecessor to a class 1a supernova.

If V445 should turn into a supernova, it would not pose a threath to Earth from a distance of 25 000 lightyears, but it would be a spectacular sight, probably even visible at daylight

Sources:
Latest arXiv publishing on the subject
ESO findings in favor of supernova
READ MORE on class 1a supernovea