The Sun is extraordinarily large. In comparison, Jupiter is a true dwarf, and accounting for more than 99 percent of all mass in the Solar System, there is no doubt about its dominance. However, the Sun can appear as tiny as a pinhead when compared to other stars in the universe. Among them is UY Scuti, a “neighbor” located 9,500 light-years away, yet the latest measurements available identify it as the largest star ever detected. How large? If we placed it in the Sun’s position, it would reach the gates of Saturn...
It is estimated that in about five billion years, the Sun will lose its hydrostatic equilibrium, its core will increase in density and temperature, and its outer layers will expand in such a way that it will end up as a red giant. Its new diameter will be large enough to “absorb” the orbits of Mercury and Venus, turning Earth into a very hot, and very dead, stone... as long as it still exists.
Now, if that makes you feel small, you need to know that compared to other stars, the Sun is insignificant. Two known examples? Antares and Betelgeuse. The “Eye of the Scorpion” is so large that its orbit would extend to some point between Mars and Jupiter if placed at the center of the Solar System, while the “Right Shoulder of Orion” would probably swallow Jupiter too. But if we follow that line of thought, it is inevitable to ask: Which is the largest star?
UY Scuti: The Reigning Hypergiant
Experts continue to point all their resources toward the sky to discover new hypergiant stars and learn more about those we have already detected. That means the throne can change at any moment, but today it belongs to UY Scuti, a red hypergiant in the constellation of Scutum.
Its record is not particularly new, dating back to the nineteenth century under the designation BD -12 5055. UY Scuti was part of a special study in 2012, conducted by astronomers using AMBER interferometry at the Very Large Telescope in the Atacama Desert.
Mind-Boggling Numbers
These astronomers determined that UY Scuti, AH Scorpii, and KW Sagittarii are at least 1,000 times larger than the Sun, and UY Scuti is the largest of that group. The most recent measurements give this hypergiant an equivalent of 1,708 solar radii (± 192), something like 7.94 astronomical units, with a margin of error of 0.89 AU.
In other words? If we take our mother star and place UY Scuti in its spot, it would reach nearly to Saturn (which at its closest point lies 9 astronomical units from the Sun). If you could travel in a spaceship at the speed of light and decided to go around UY Scuti, that trip would take seven hours, versus 14.5 seconds for the Sun.
But the most striking thing about this star and other similar hypergiants is that they are not so “massive.” UY Scuti would have reached its current state with about 25 solar masses, losing more than half during its evolution.
Do you feel small now?
It is worth noting that UY Scuti might not hold the crown forever; recent information suggests it may have already been surpassed. read more here.
