# How big is Stephenson 2-18, the largest known star in 2022?

Stephenson 2-18 is a supergiant red star located in the constellation Scutum, ≈18,900 light-years from Earth. Because of its size, it may even belong to the category of red hypergiant stars in the Hertzsprung-Russell diagram.

While Earth has an average diameter of ≈12,742.02 kilometers, Stephenson 2-18’s diameter is estimated to be ≈3,003,000,000 km or ≈74,934.47 Earths threaded. Or, ≈2,158.88 Suns threaded with an average diameter of ≈1,391,000 km each. Or ≈1,687,000,000,000 Chuck Norris standing on top of each other measuring 1.78 meters (1.687 trillion corresponds to ≈5.6 × the number of stars in our galaxy, ≈300,000,000,000).

The equatorial circumference of our planet is ≈40,075,02 km, which takes light ≈0.13367587 seconds to circle it (speed of light: ≈299,792 km/s or 1,079,000,000 km/h). The equatorial circumference of the Sun is ≈4,371,000 km or a travel time of ≈14.58 seconds for light. However, the equatorial circumference of Stephenson 2-18 is ≈9.43×10^9 or ≈9,430,000,000 kilometers, for which light needs ≈8 hours 44 minutes 15.09 seconds. A Tinder chat between the North and South Poles would be akin to a test of patience.

The average cruising speed of an Airbus A380 is ≈945 km/h, making it circle the Earth’s equator in ≈42.41 hours (at ground level) and circle the Sun’s equator in ≈4,625.40 hours or 192.72 days. At the same speed, a flight around Stephenson 2-18’s equator would take an A380 about ≈9,978,835.98 hours or ≈1,139.14 years. To stick with silly comparisons: The typical human walking speed is ≈4 km/h. In this regard, it would take a human ≈2,357,500,000 hours or ≈269,121 years to complete a single walk around Stephenson 2-18 (without a break). At the same time, ≈9,618 human generations would have lived, with one generation followed by a new one every ≈27.98 years on average.

Or short: Stephenson 2-18 is huge. Big. Gigantic. Supercalifragilisticexpialidocious.

And the above comparisons deeply amateurish.

Hero image: Sun Emits a Solstice CME by NASA Image and Video Library.

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