Betelgeuse gets smaller…, plus the newest largest star

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.