SN 2008ax was a helium-rich type Ib core-collapse supernova in the interacting galaxy NGC 4490.

[3] X-ray emissions were detected from the event, which are most likely the result of shock heating from the supernova ejecta and circumstellar material.

[8] Images of the source location made using the Hubble Space Telescope in 2011 and 2013 were used to identify the progenitor.

However, this is not favored by models which indicate the progenitor had a relatively low mass of 4–5 M☉ and extended hydrogen-rich atmosphere with a radius of 30–40 R☉.

An alternative, more plausible model suggests the progenitor was part of an interacting binary system where much of the atmosphere was lost through mass transfer to the companion.