The Heaviest Known Star Packs 315 Suns of Mass Into Only 30 Times the Sun's Width
It gives off close to nine million times as much light as the Sun while shedding huge amounts of gas every second.
Kurzgesagt – In a Nutshell · The Largest Star in the Universe – Size ComparisonThe most massive known star, R136a1, packs 315 times the Sun's mass into a ball only about 30 times as wide.
That extra mass makes it much brighter, not much wider. R136a1 gives off close to nine million times as much light as the Sun.
Its gravity only just keeps it intact, and it sheds about 321 trillion tons of gas every second in a wind streaming off its surface.
This fits a wider pattern: very bright, massive stars stay modest in width, so more mass does not mean a much wider star. Beta Centauri, a star system, holds two such stars that each put out about 20,000 times the Sun's power from a body only 13 times as wide.
When such giants first ignite, they burn so hot that the heat blows away surrounding gas. That caps how massive such a star can get at about 150 times the Sun's mass.
Questions people ask
Where is R136a1?
It is in a dense cluster called R136, in the Tarantula Nebula in the Large Magellanic Cloud, a small satellite galaxy of the Milky Way about 163,000 light-years away. It was identified as the record holder after astronomers weighed its light and heat with large telescopes.
Why doesn't more mass make a much bigger star?
In massive stars, gravity squeezes the core so hard that fusion runs extremely fast, producing huge outward pressure and brightness without needing much extra volume. Adding mass mainly makes the star denser, hotter, and brighter, not proportionally wider. The truly huge stars are dying stars whose outer layers have puffed up.