Some stars are average, just like our Sun. Some stars are tiny, like white dwarfs or neutron stars. Some are huge and dwarf our Sun by many thousands of times. Some barely shine amongst the darkness of space and others light up skies across hundreds of galaxies. However, making precise measurements across quadrillions of miles and million of years in time – is quite difficult to say the least. Thus, none of these should be taken as gospel fact. Our understanding of the Universe is an ever-changing process, but for now these are the stellar anomalies that come out top of their fields.
The Biggest Star
This one comes down to two contenders: UY Scuti and NML Cygni. UY Scuti is the more likely candidate, clocking in at 1708 solar radii (or 1708 times the radius of the Sun) which is equal to 1.5 billion miles. With a very small margin of error, scientists can confidently state that UY Scuti has knocked the previous well-known contender VY Canis Majoris, off of the top spot. Even at 9,500 light years away in the constellation Scutum – that’s five and a half quadrillion or 5,580,000,000,000,000 miles – UY Scuti is bright enough it was first seen by astronomers on Earth in 1860.
Sirius, The Dog Star, has long been known to humans as the brightest star in our night sky – as visible to the naked eye. But what looks bright here to us on Earth, is not the same as the brightest (or most luminous) star out there. That award goes to the rather boringly named R136a1. This star is so bright, we can get accurate measurements of it even though it is in another galaxy entirely. R13 is in the Large Magellanic Cloud, an orbiting satellite galaxy of our own Milky Way. It weighs in at 8.7 million times the standard luminosity of the Sun.
Lastly, the brightest object ever visible on Earth without a telescope was a supernova (or exploding star) that occurred in 1086, imaginatively called SN1086. This explosion was 9500 light years away yet lit up the night sky brighter than Venus and was even visible in the day for several months of that year.
The smallest hydrogen burning star, below which they are put into a separate category of brown dwarf planets, is EBLM J0555-57 in the constellation Pictor. It has an average radius of 60,268 km, about the same size as Saturn and around 10 times that of Earth. In comparison our Sun is about ten times as big as that at 139 million kilometres.
The smallest known stellar remnant (what is left behind after a star goes supernova and explodes) is pulsar star PSR B0943+10 – which has a radius of less than three kilometres. This tiny object is extremely dense, fitting about 2% of the Sun’s mass into a space millions of times smaller. It also shoots radio wave and x ray beams out into space with more force than millions of atomic bombs every few seconds too, so don’t get that close!