Using the most advanced technology, the various space agencies around the world are slowly piecing together the bodies that make up our galaxy. Every day seems to bring something new and the only thing we can rely on is that the universe will only continue to astound us. Our sun is the reason for life on this planet. Without it, every living thing would die. Yet it is quite unremarkable in many ways – it is fairly stable compared to most and is not particularly large either. So which are the largest stars in our galaxy? If we take the sun as the base size, giving it a radius of 1 unit…
Approximately 7800 light years from Earth, this red hypergiant is the 38th discovered star in the constellation of Scutum. Though it is bright, it is only of the 11th magnitude when seen from Earth. Were it not for a dust cloud dimming its appearance, it would be on the 5th magnitude and far more visible. Sky watchers should be able to see it with a good pair of binoculars. How big is it? It is 1708 times the radius of our sun.
This red hypergiant is the around 5300 light years from Earth and is one of the most luminous cool hypergiants. At 1650 times the radius of the sun, in context if we put the star in the place of our sun, its surface would extend to beyond the orbital plane of Jupiter and halfway to Saturn. As its name suggests, it is in the constellation of Cygnus. Red hypergiants do not live long; researchers estimate their lifespan in millions of years.
VY Canis Majoris
Another red hypergiant, not only is Canis Majoris one of the largest stars, it is also one of the most luminous. It is approximately 1420 times the radius of our own sun and some 3500 light years away. It was first identified at the beginning of the 19th century and it has been calculated that the star has been fading since around 1850. It may have once been a multiple star – there are six separate components that make up the body, including a surrounding nebula. Unlike many other examples in its class, it does not have a companion star.
This star is located in the Westerlund 1 super star cluster, areas known for birthing new stars, and is anywhere between 9000 and 16000 light years from Earth. It is only slightly smaller than WHO G64, measuring at around 1530 the radius of our sun, still putting its surface in the area of Jupiter’s orbital plain. In 2013, The European VST identified a cloud of ionized hydrogen – the first nebula discovered around a red star.
Between 3000 and 5000 light years from our own sun, this red supergiant is estimated to be around 1520 times the radius of our own sun. Unfortunately, accurate measurements are difficult as it pulsates, erratically at times, and the estimation of its size is a conservative one. When a star pulsates, it grows and shrinks and changes its luminosity and spectrum. There are two types: radial where the whole star changes, and non-radial where only parts of it grow and shrink.