iPTF14hls

iPTF14hls is an unusual supernova star that erupted continuously for about 1,000 days beginning in September 2014 before becoming a remnant nebula. It had previously erupted in 1954. None of the theories nor proposed hypotheses fully explain all the aspects of the object.

== Observations == thumb|left|A green-light light curve for iPTF14hls, plotted from data published by Sollerman et al. The star iPTF14hls was discovered in September 2014 by the Intermediate Palomar Transient Factory, and it was first made public in November 2014 by the CRTS survey as CSS141118:092034+504148. Based on that information, it was confirmed as an exploding star in January 2015. It was thought then that it was a single supernova event (Type II-P) that would dim in about 100 days, but instead, it continued its eruption for about 1,000 days while fluctuating in brightness at least five times. The brightness varied by as much as 50%, going through five peaks. Also, rather than cooling down with time as expected of a Type II-P supernova, the object maintains a near-constant temperature of about 5000–6000 K. Checks of photographs from the past found one from 1954 showing an explosion in the same location. Since 1954, the star has exploded six times.