Here’s the thing, science has told us that the universe is 13.8 billion years old. However, if the universe is 13.8 billion years old then we ask, how can a star be more than 14 billion years old?
Well, here we are going to look at the oldest star that we can see and talk about all things astronomy.
For hundreds of years, astronomers have been observing a star that is located approximately 190 light years away from the Earth within the constellation Libra. This star journeys quickly across the sky at 800,000 miles per hour.
What is more fascinating than the speed of the star? Well, this star is known as Methuselah, or HD 140283, and it is one of the universe’s oldest known stars.
This star causes a pretty big problem because it outlives the start of the universe - after all, how can the universe be younger than a star?
Well, over many years the age of the star has been disputed, but gradually scientists have narrowed it down to 13.8 billion years old.
Gradually as science has advanced then a much greater understanding has been established in relation to stars and their properties. There are a range of factors that contribute to working out the age of a star such as the amount of oxygen in the star.
The reason why it took so long to establish the age of the star is due to random and systematic errors. Scientists had to push the error bars to their extreme limits.
However, the very existence of this star is a strong contributing factor to the Big Bang theory.
How Long Does A Star Live For?
So, a star with the same mass as our sun can live for as long as 10 billion years, however, a star that weighs 20 times as much will only live for 10 million years, which is approximately a thousandth as long. This is all to do with the energy that the stars can give off, and how large the star is.
The lifespan of a star is determined by the size that it is, but stars can live at different lengths of time, which again all depends on their size. Stars begin their lives as dense clouds of dust and gas, and after a star forms it burns hydrogen into helium.
Once hydrogen begins to run out, more burning will occur and an example of this is the burning of helium into much heavier elements.
If the size of the star is less than several times the mass of the sun, then it will eventually become a white dwarf. Alternatively, if the star is bigger than the mass of the sun then it will firstly implode and then it will actually explode in a supernova explosion.
Which Star Has The Shortest Life Expectancy?
So, we have talked about the size of a star determining its lifespan - so naturally, the smaller the star then the longer it will live. The bigger the star, the faster it will burn up. These stars can burn out and explode in a supernova after just a few million years of fusion.
A star with a mass like the Sun can instead continue to fuse hydrogen for approximately 10 billion years. Additionally, if the star is really small then it can keep fusing hydrogen for up to a trillion years.
The largest main sequence stars, spectral type O, have the shortest lifespan of all the stars of just 10 million years, which in cosmic time is practically the blink of an eye. These stars have a pretty short lifespan and end in a supernova, then they typically become a black hole.
What Is The Explosion Of A Dying Star Called?
This is a word we have used throughout this article, so it might seem kind of obvious at this point. But, the explosion of a dying star is called a supernova. A supernova can give off more energy in a few seconds than our sun will radiate in its own lifetime. In fact, NASA calls a supernova ‘the largest explosion that takes place in space.’
This is a pretty spectacular event that can be so bright that they actually outshine their entire galaxies for a few days, or in some cases they can outshine their entire galaxies for months.
After the supernova, all that actually remains is a dense core and a hot cloud of gas called a nebula. The supernova is actually the biggest explosion that humans have ever seen. Within these explosions, each blast is the bright and powerful explosion of a star.
The cause of a supernova is essentially because these massive stars burn large amounts of nuclear fuel right at their cores, or right at their centers. So, this produces a vast amount of energy, and as a result of this the center of the star gets really hot.
This heat generates pressure, and it is this very pressure created by a star’s nuclear burning that actually stops the star from collapsing. This is because a star is in a limbo between two opposing forces, these are all to do with pressure.
The star’s gravity will attempt to squeeze the star into the most miniscule and compact ball, but the nuclear fuel that is burning within the star’s core gives off a strong pressure coming outwards.
This outward push will resist the inward squeeze of gravity, and all of these elements work together as a way of holding the star together.
Overall, the lifespan of a star is determined by a number of factors. The main one that we have established throughout is the size of the star.
This is due to the fact that the bigger the star is, the shorter its lifespan. However, the smaller a star is then the larger the lifespan it will have. This is where we have introduced you to the Methuselah which is the oldest star in the universe.