How Big Can a Star Actually Get?

Put the biggest star ever pictured where the Sun is, and Earth and Jupiter would both sit deep inside it. So why don't stars grow even bigger? There are two records: the widest star and the heaviest star are different objects. We follow R136a1, the most massive star known, the Eddington limit, where a star's own light pushes back against gravity, and the swollen red supergiants like Betelgeuse, UY Scuti and WOH G64, whose sizes still come with honest error bars. And a study posted in 2026 argues that both ceilings come from the same place: light. Sources: ESO, NOIRLab, NASA, NASA Chandra, Joyce et al. (2020), Davies et al. (2018), Arroyo-Torres et al. (2013), Figer (2005), Sanyal et al. (2015), Owocki (2014), Crowther et al. (2010) and Sabhahit & Vink (2026, preprint). 0:00 Why can't stars grow bigger? 0:30 How big is a big star? 1:40 Is the biggest star the heaviest? 2:48 What stops a star getting heavier? 4:13 So how does R136a1 exist? 5:31 What limits how wide a star gets? 6:52 So how big can a star get?