[이광식의 천문학+] What is the size of the largest star in the universe? Giant “Stevenson 2-18”: ZUM. new



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Size comparison of the Sun and Stevenson 2-18

It would be interesting and meaningful to enhance our cosmic sense of “size.” First, if we were to capture the largest object around us, it would definitely be the Sun. It is 109 times the diameter of the Earth, where 8 billion people live, and 1.3 million times its height. The sun is such an absolute being in the solar system that it is embarrassing to say that the sun rules the solar system. It makes up 99.86% of the mass of all celestial bodies in the solar system.

Even this sun is nothing more than a dwarf if transported into the galaxy and into space. This is the reason why there are so many massive stars in the universe. Stars of massive size are called giants, and even the well-known supergiant Betelgeuse in the constellation Orion has a diameter more than 1,000 times the diameter of the Sun. If this star were pulled towards the Sun, it would be roughly the size of Jupiter’s orbit.

However, it’s not uncommon for stars to call Betelgeuse frivolous. The VY Canis Majoris (VY Canis Majoris) detected in the constellation Canis Major was confirmed to be 2069 times that of the Sun following observations in 2020. It is larger than the orbit of Saturn. Although it was previously known as the largest star in the history of observation, more complex observations show that the radius is much smaller than previous measurements. It is approximately 3900 light years from Earth.

A massive supergiant that has clearly surpassed VY Canis Major to become the largest star has emerged, a star called Stevenson 2-18 discovered by American astronomer Charles Bruce Stevenson in 1990.

The brightest red star in the center is Stevenson 2-18. The bright stars above are the Stevenson Star Cluster 2.

One of 40 red giants in the open cluster Stevenson 2, located in the constellation Shields, about 20,000 light-years from Earth. It does not belong to the arm of Orion, the spiral arm to which the Earth belongs, but to the arm of the whole other constellation Cruciatus-Shield.

So how big is this star? Its diameter is about 2.9 billion km, or 2,150 times the diameter of the Sun. It will take more than 8 hours to orbit this star at the speed of light, and it will take 1,100 years to circle the star at a speed of 900 km/h. It far exceeds the combined period of the Goryeo and Joseon dynasties. If this star is dragged in place of the sun, it will engulf Saturn’s rings and moons. Can you imagine a thing being that big? Of course, this star belongs to the Milky Way, but astronomers in general strongly believe in the isotropism and monotheism of the Universe, which means that it is not so much to consider it the largest star of the universe.

The largest star in the universe, Stevenson 2-18, is around 14 to 20 million years old, like the other stars in the cluster, making it very young compared to other stars. As stars grow, their lifespan decreases dramatically. Indeed, the larger the star, the faster the nuclear fusion, which consumes a huge amount of nuclear fuel.

Stevenson 2-18 is expected to die in a supernova explosion millions of years from now and then turn into a black hole.

Or Kwangsik Lee Science columnist joand999@naver.com

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