Is Our Sun The Biggest Star?
Earth vs. Sun and Sun vs. Uy Scuti Side-by-Side Comparisons: Earth is only one
pixel in this illustration compared to the enormous size of our Sun. However, Uy Scuti and
our Sun side-by-side reveal that our Sun is difficult to see, with only 1 pixel in this
illustration. More than 4.98 billion Earths could fit inside Uy Scuti!
Our Sun - The Yellow Dwarf: First, let's look at our Sun, which is known as a yellow dwarf star; on average, it is about 92.956 million miles (149.60 million km) away from Earth. The name "yellow dwarf" is somewhat deceiving. When we compare the size of the Sun to the size of Earth, the Sun, is massive and has no competition with any other celestial object for size in our Solar System. Earth's diameter is only 7,926 miles (12,756 km), and the Sun's diameter is approximately 864,576 miles (1,391,400 km), which is about 109 times that of Earth's. The circumference of our Sun is approximately 2,716,146 miles (4,371,213 km). In short, that's approximately 2.716 million miles (4.371 million km). A person would have to travel around Earth's equator about 109 times to equal only one trip around the Sun. Amazingly, the volume of our Sun could hold nearly 1.3 million Earths! As massive as our Sun may seem, even though its name, "yellow dwarf," seems to imply otherwise, there are stars throughout the known Universe that are much larger!
Enter - Uy Scuti – The Red Supergiant! This star is no other than the red supergiant Uy Scuti - located about 9,500 light-years away from us: that's approximately 55.85 quadrillion miles (89.88 quadrillion km). Its diameter is an incredible 1.48 billion miles (2.38 billion km), giving it a circumference of roughly 4.639 billion miles (7.466 billion km).
Grasping The Massive Size: To help grasp the massive size of Uy Scuti, we will give the example of the International Space Station (ISS) orbits Earth about 260 miles (418 km). It makes one complete orbit around the entire Earth in approximately 92 minutes, about 15½ times per day (every 24 hours), traveling at about 17,150 mph (27,600 km/h), about 4.76 miles (7.64 km) per second, covering about 411,600 miles (662,406 km) in 24 hours. However, as fast as this may seem, it would still take the ISS about 30 years and 10 months to complete the equivalent distance of just one orbit around the massive red supergiant Uy Scuti's equatorial circumference of about 4.639 billion miles (7.466 billion km)! The Sun has an equatorial circumference of approximately 2.716 million miles (4.371 million km). Therefore, it would take just a little more than 6½ days for the ISS to cover an equivalent distance of one orbit around our Sun compared to 30 years and 10 months for it to orbit Uy Scuti! The difference is astounding!
Uy Scuti isn't visible to the naked eye, with an apparent variable magnitude of 8.29 maximum to a minimum of 10.56 (the lower the number, the brighter the star). Therefore, a binocular or telescope is necessary. The typical cutoff point for naked-eye viewing is an apparent magnitude of about 6.5 - assuming a clear, dark sky with little to no light pollution. Additionally, Uy Scuti is a dust-enshrouded star, which adds to the inability for good observation.