In the year 2020, many astronomers thought the red super giant star Betelgeuse would go supernova before our eyes. It didn’t –we haven’t seen the light from the event yet – but instead we did come to find that this monster of a star is smaller in size, and even closer to Earth than we first realized.
Betelgeuse holds the title of the nearest supergiant star to the Earth, at – now – 530 light-years (ly) from Earth (previously, Betelgeuse was determined to be 25% further away, at 660 ly). Its diameter was refined to a similar extent, decreasing from Jupiter’s orbit-size to a third smaller; in other words, now 750 times the Sun’s diameter.
Betelgeuse is still one of the largest stars we know of, but now we know it to be a bit smaller and closer.
Speaking of big stars, we very recently crowned the newest largest star by diameter that we know of. The “Stephenson 2-18” (St2-18) is located in a cluster in Scutum named Stephenson 2. The constellation Scutum is also home to the last title-holder: UY Scuti.
St2-18 and UY are both “evolved” red supergiant stars, meaning they’re on their last legs before supernova, just like Betelgeuse. St2-18 has a diameter 2,150 times that of our Sun, meaning this star if placed instead of our Sun in the Solar System would sit with its surface at Saturn’s orbit.
While St2-18 is the biggest known star, the title of “heaviest” belongs to the so-called “Pistol Star” which is a blue hypergiant found in the Central Cluster of stars about the core of the Milky Way galaxy. Its mass is 100 times that of our Sun or more.