What was the approximate initial mass of a star like Antares, observed as a red supergiant?

Perhaps twenty times the Sun's mass ($20 M_{\odot}$)

Specific, highly evolved stars provide concrete examples of evolutionary endpoints dictated by mass. Antares is specifically cited as a red supergiant, placing it firmly in the high-mass category destined for supernova rather than becoming a white dwarf. The text states that such a star was likely born with an initial mass around twenty times that of the Sun ($20 M_{\odot}$). This significant initial mass reservoir provided the necessary gravitational energy to sustain fusion through multiple, increasingly complex stages, including silicon burning, resulting in its current colossal volume and classification as a red supergiant, which is far larger than the expansion achieved by a standard red giant.