Apparently not. But when you speak of ‘bigness’ among stars, you need to define your terms. There are very heavy stars. And there are gigantic stars, in terms of sheer physical size.
UY Scuti, a bright red supergiant variable star that resides 9500 light years away in the constellation Scutum is currently believed to be the largest star in the Milky Way galaxy, size-wise. German astronomers at the Bonn Observatory discovered UY Scuti in 1860, but it wasn’t until astronomers observed UY Scuti through the Very Large Telescope in Chile’s Atacama Desert in 2012 that the star’s true size became well documented.
Following this discovery, UY Scuti was officially named the largest known star in the galaxy, surpassing previous record holders such as Betelgeuse, VY Canis Majoris, and NML Cygni.
Of course, there are stars that are brighter and denser than UY Scuti, but it has the largest overall size of any star currently known, with 1,708 times the solar radius, and an estimated 21 billion times the volume of the Sun but only between 7 and 10 solar masses. Well, these are numbers - and it is not easy to actually picture the size. So, to give you a better perspective, we need to swap the Sun with UY Scuti and look at the solar system:
The Star would engulf most of Jupiter’s orbit, taking in the Sun, the first five planets of our solar system, and the asteroid belt. Some astronomers speculate the star may be even larger, enough to extend beyond the orbit of Saturn. Not only that, but the UY Scuti’s gravity would be so strong, the larger planets and even the distant planetoids of our solar system will fall into the star, and whatever remained would take thousands of years to complete a single orbital rotation around the giant star. (Needless to mention,this is not a real picture of UY Scuti. There are currently no telescopes able to provide an image bigger than a small dot. The image used is a modified picture of the Sun.)
In terms of sheer mass, the top spot goes to R136a1 - a star located in the Large Magellanic Cloud, some 163,000 light-years away. It is believed that this star may contain as much as 315 times the mass of the Sun, which presents a conundrum to astronomers since it was believed that the largest stars could only contain 150 solar masses. The answer to this is that R136a1 was probably formed when several massive stars merged together. Needless to say, R136a1 is set to detonate as a hypernova any day now. You have heard the phrase - the bigger they come, harder they fall.
UY Scuti is still the leader in the largest star category. The largest star and one of the most luminous of its kind is 2.9 kiloparsec(9500 lightyears away).
With an estimated radius of of 1,708 solar radius, the star's photosphere would atleast engulf orbit of jupiter. There are possibilities of a star being bigger than UY SCUTI but it has to be discovered yet.
There most likely are. There have been papers published mentioning that a star has a limited maximum size and that UY Scuti is really close to the maximum limit. But this is also what was said about VY Canis Majoris, the previous title holder for the largest star found. We understand more and more about these hyper giant stars every time we find new ones. So our understanding is always updated and theories need to be modified and updated accordingly.
But weshould note that that all these hyper giant stars are within our galaxy alone. UY Scuti is around 9500 light years away from Earth. This means that with our galaxy (being 100,000 light years across) alone, there might be many more candidates. Enlarge the scope to all galaxies in the observable universe and statistically speaking, there are definitely more than a billion stars that should fall within the size range or are bigger.
We are currently limited by our technology. At the huge distances that they are from the Earth, we have not progressed enough to measure far away stars (even within our galaxy) precisely. As we update ourselves, I’m sure there will be many more of these stars out-titling each other for glory of being the largest one.
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