If a Quasi-Star Entered Our Solar System?
5The Largest Star in the Universe – Size Comparison
Galactic bohemoths
The star with possibly the largest radius is currently UY Scuti a variable bright red supergiant in the constellation of Scutum. Located around 9,500 light years from Earth, and composed of hydrogen, helium and other heavier elements similar to the chemical composition of our Sun, the star has a radius 1708 (±192) times larger than our Sun’s.
That is nearly 1.2 billion km, resulting in a circumference of 7.5 billion km. To put that in perspective, it would take you 950 years to fly around it in a commercial airliner – even light would take six hours and 55 minutes to circumnavigate it. If it were to replace our Sun, its surface would be located somewhere between the orbits of Jupiter and Saturn – needless to say, Earth would be swallowed up.