Stars are some of the most widely recognized astronomical objects and are very common in space. There are billions of stars in the Milky Way alone, and their abundance means that there are actually lots of different kinds of stars and each type has its own unique features. Today’s focus are the very cool, very beautiful blue giant stars.
For example, our Sun is a yellow dwarf star which means that it is quite small and bright. They are very common, and there are lots of them in our galaxy alone.
But yellow dwarf stars are just one class in a range of star types and in fact, stars come in lots of different sizes and colors. Here, we are going to be looking at a certain class called blue giants.
If you want to learn more about stars, then this is the place for you. We are going to give nine interesting facts about blue giant stars and what makes them so special compared to the rest of their stellar brethren.
So – let’s jump right in!
Fact Number One: Blue Giant Stars Are Both Huge And Small
Compared to a lot of things in space, we humans are actually very, very small. Other planets easily outsize even our planet Earth in our solar system like Jupiter and Saturn, and even they are outsized by the Sun.
However, the Sun itself is actually classed as a dwarf star, so this means that even though it is huge when compared to us, it is actually very small when compared to the sizes of other stars like blue giants.
Blue giants range drastically in mass and size, but on average, they are about 5 to 10 times bigger than our Sun. There is even a subgroup of blue giants known as a blue supergiant which are the largest forms of blue giants.
Again, they vary in size, but the most commonly known example of a blue supergiant is Rigel, a star found in the Orion constellation that is estimated to be between 20 to 25 times the mass of the Sun.
This means that to us, blue giants are huge stars – but there is always a bigger fish.
On the overall scale of star sizes, blue giants actually sit somewhere in the middle. While larger than the sun, blue giants are still smaller than other types of stars, including red supergiants and hypergiants. This means that realistically, on average, blue giants are not that giant at all!
Fact Number Two: Blue Giants Are Hot
This fact may seem like a no-brainer but the truth is that even when compared to other stars, blue giants are very hot.
The surface of the Sun is nearly 10,000 degrees Fahrenheit (that’s 5,500 degrees Celsius) or 5,800 kelvin. That is roughly around 172 times hotter than the surface of the Earth which, while it seems extremely hot, is nothing when compared to blue giants.
The average blue giant has a surface temperature that blazes at 20,000 kelvin – that’s nearly four times hotter than the Sun! When converted to degrees Fahrenheit, this means that blue giants can burn at 35,500 degrees (that’s nearly 20,000 degrees Celsius)!
And those blue supergiants? They burn even hotter. The star Rigel in the Orion constellation has been measured to reach temperatures as high as 50,000 kelvin which is nearly 90,000 degrees Fahrenheit or 50,000 degrees Celsius.
So, even though blue giants may not be the largest type of star out there, it is definitely one of the hottest!
Fact Number Three: Blue Giants Are Bright
Stars are some of the brightest objects in space, which is why we can see them from Earth from millions of miles away. The Sun itself is actually 93 million miles and yet, that is the closest star to us on Earth and is easily the largest star in our sky.
So, those stars that appear as tiny little dots in our night sky must be extremely bright – and they are!
A lot of the brightest stars are blue giants, including the most luminous star recorded by us. This star is the blue supergiant R136a1 which is estimated to shine nine million times brighter than the Sun!
The reason why blue giants are so luminous and bright is that they emit so much energy. We mentioned earlier that blue giants are some of the hottest stars in space, so this means that they burn up a lot of fuel in a short space of time to emit such high temperatures.
Another result of this means that they also generate more energy than other stars. For example, R136a1 is thought to generate more energy in just four seconds than the Sun does in an entire year!
So not only are blue giants incredibly hot, but they are also very bright, allowing them to be seen from thousands of light years away!
Fact Number Four: Blue Giant Stars Are Short-Lived
There is a simple saying that applies to stars and their lifetime – the brighter the star, the quicker it dies.
This is because all stars have a limited amount of fuel. This fuel is made from fusing hydrogen into helium, and this process is what they use to shine so brightly and emit such high amounts of energy.
However, because the amount of hydrogen each star has is limited, they eventually use it all up and die – and blue giants are some of the most short-lived stars out there.
Blue giants are seriously bright stars but this is because they are fusing more hydrogen together per second than other stars like our Sun does. This means that they will eventually use up their hydrogen sooner than other stars do and die out.
There is also a rule of thumb that the larger the star, the shorter it lives for. A tiny red dwarf can survive for trillions of years, and our Sun will last for billions, but blue giants only live for around 10 million years.
10 million years may be a seriously long time for us humans but in the larger context of the universe, blue giants are very short-lived when compared to their smaller counterparts.
Fact Number Five: Blue Giants Do Not Have Their Own Planets
Stars are massive, so most of them have a few planets that orbit around them. Our Sun has many planets that make up our solar system, for example.
However, out of all the stars confirmed to have planets orbiting them, not a single one is a blue giant.
This is very unusual for stars but there could be a very basic reason behind this. Planets that form around stars take billions of years to properly be born and as we discussed above, blue giants simply do not live that long. They live their lives bright but short – and not nearly long enough to form any of its own planets.
Some astronomers also believe that the reason why blue giants do not have planets is because they also emit very strong solar wings. Solar winds are a constant flow of particles that stars emit, and because blue giants emit so much energy, their solar winds are stronger than other stars.
This can make it very difficult for planets to form around a blue giant.
Fact Number Six: Some Blue Giants Are Unstable
Blue supergiants are a very interesting type of blue giant stars because not only are they massive and luminous, but they are also very unstable.
This is because blue supergiants live very close to something called the Eddington limit. The Eddington limit is used to describe the balance that keeps stars in shape.
All stars retain their shape by emitting an equal amount of radiation (in this situation, energy) to the force of gravity that pulls it back inwards. This balance is vital for keeping a star alive and in shape and if one were to become more powerful than the other, then the star would destroy itself and die.
Blue supergiants are one of the many types of stars that live dangerously close to this limit. They have high mass loss rates and very high luminosity which makes them unstable because the Eddington limit is constantly being pushed and tested due to this.
Every second that goes by brings them closer to the end as each force battles against the other, one pushing and the other pulling, and just one of these forces needs to be slightly stronger than the other for just a second for it all to end for that blue giant.
This makes them extremely dangerous and could also play a part in why their lifespans are so short – they are unstable and are just a split second away from destruction at any given moment.
Fact Number Seven: Some Blue Giants Can Turn Into Black Holes
All stars die, but some die a bit more dramatically than others – and blue giant stars are part of that group.
Some stars die quietly and just shrink into cold cores, but due to their enormous mass and power, blue giants do not die quietly. It is theorized that when they have fused all of their hydrogen and their energy output is lower than the force of gravity pulling it inward, blue giants collapse on themselves and die in a huge explosion known as a supernova.
These explosions are some of the most deadly known to us on Earth – the total energy output in that split second is on average equal to the amount the Sun will emit in her entire lifetime! And that’s not all – blue supergiants (which are far heavier again than regular blue giants) can even transform into black holes!
Black holes are the densest objects in our known universe as their gravitational pull is so strong that even light cannot escape them. This is why through telescopes, black holes appear to be – well, black holes.
Light that has gone near them is not able to reflect back into our eyes, so they appear to be holes of nothing. What black holes really are made of is the remnants of a dead star- and some of them may be dead blue supergiants.
However, the only issue is that we are yet to actually see this happen. How a blue giant dies is answered using theories because astronomers have yet to see one die. This is because stars can live for millions to trillions of years so it could be a long time before any of the blue giants in our observation are ready to go supernova.
So, astronomers have no choice but to observe how other stars die and draw comparisons until they are finally able to observe the death of a blue giant to either confirm or prove their theories wrong.
Fact Number Eight: There Are Different Types of Blue Giants
Blue giants themselves are not an actual class of stars. In reality, the term ‘blue giant’ is just a name often given to really large, really bright, and really hot stars that we have observed from Earth.
There are actually seven official types of stars that are each assigned a different letter of the alphabet. The hottest, largest, and brightest stars are categorized as Type O and these stars are also the rarest. Many blue supergiants fall into this category, but not all blue giants do.
Some blue giants fall into a more common group of stars called Type B. These stars are less massive and do not burn as bright, which also lengthens their lifespan when compared to stars in Type O. The star Rigal, despite its huge size and luminosity, actually calls in Type B while other blue supergiants like the star Alnitak fall in Type O.
This means that there are actually different types of blue giants and they do fall into different categories.
Fact Number Nine: We Are Still Learning About Blue Giants
Space is never ending, so every day brings astronomers a new chance to discover something new. This means that we are still constantly learning more about the things around us in the universe so there is always the potential for something new and exciting to be discovered about blue giants.
Maybe one day, we will wake up to a new type of blue giant or one that actually does have planets orbiting it – who knows? There is still so much to learn and research about blue giants that every single day brings us a step closer to a new discovery!
Those were nine interesting facts about some of the brightest and most massive stars in our universe – the blue giants!
Although some differ from each other when it comes to mass and luminosity, it is generally agreed that all blue giants are large stars that are extremely hot and bright. They are constantly being researched around the world by astronomers in lots of different countries, so every day brings us a step closer to understanding these special stars and unraveling their mysteries just a bit more.
There is no doubt that they are some of the most beautiful objects in our universe, and now you can observe with the confidence of knowing a lot about them yourself.