Questions about stellar evolution

In summary: Overall, it is possible to make a good approximation of the average temperature on a fictional planet without taking the absorption factor into account, but taking it into consideration will provide a more accurate result.
  • #1
AvengerDr
3
0
Hello there!
I'm developing a "4x" game a-la Master of Orion. I was coding some algorithms to help me generate a somewhat realistic galaxy.

I'd like to know if it is possible to compute the time that a main sequence star will spend in its subgiant and giant status. For example, given the mass I can determine all other values (luminosity, effective temperature, lifespan, etc), but I'd like to know those values. In fact in the game, each star is given a random "age" in billion years. Depending on this value, I can "evolve" the star off-the main sequence. But depending on how many years have passed the star could have become a sub giant, a giant, a white dwarf, a neutron star or a black hole.

Another question I had, what would be the best way to determine the average temperature on a planet, given its orbital radius and the star's luminosity? I've read about blackbodies, but as I've understood, not all planets would be perfect blackbodies, so the absorbtion factor would need to be corrected. But what approaches do you think I could follow when talking about fictional planets? Is this corrected value necessary or a good approximation can still be found without it?

Thanks for the answers :)

More info about the game I'm developing can be found http://www.avengersutd.com/wiki" [Broken].
 
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  • #2
Regarding the time a main sequence star will spend in its subgiant and giant status, the exact amount of time can be difficult to calculate since it is based on many factors such as the initial mass, metallicity, rotation, and other internal processes. However, there are some general trends that can be observed. Generally, stars with masses between 1-8 solar masses will spend about 10% of their total lifetime as a subgiant, and about 2-3% of their lifetime as a giant. Stars with masses greater than 8 solar masses tend to spend a higher percentage of their lifetimes as subgiants and giants. As for determining the average temperature on a planet given its orbital radius and the star's luminosity, you can use the Stefan-Boltzmann law, which states that the total energy emitted by an object per unit area is proportional to the fourth power of its temperature. You can use this equation to calculate the average temperature of a planet, taking into account the absorption factor (which accounts for the albedo of the planet) and the distance of the planet from the star. It is important to note that the absorption factor will vary depending on the type of planet (i.e. its composition, atmosphere, etc.).
 

1. How do stars form?

Stars form from giant clouds of gas and dust called nebulae. As gravity pulls the material together, it becomes more and more dense and begins to heat up. When the core reaches a high enough temperature, nuclear fusion begins and a star is born.

2. What is the main factor that determines a star's lifespan?

A star's lifespan is determined by its mass. The more massive a star is, the shorter its lifespan will be. This is because larger stars burn through their fuel at a faster rate, causing them to die sooner.

3. How does a star's mass affect its evolution?

A star's mass plays a crucial role in its evolution. A star's mass determines its temperature, luminosity, and lifespan. The more massive a star is, the hotter and brighter it will be, and the quicker it will exhaust its fuel and die.

4. What happens to a star after it runs out of fuel?

Once a star runs out of fuel, it will begin to die. The exact process depends on the star's mass. Smaller stars, like our Sun, will become red giants and eventually white dwarfs. Larger stars will go through a series of explosions, such as supernovae, before becoming a neutron star or black hole.

5. Can stars change their size and brightness over time?

Yes, stars can change their size and brightness over time. This is known as stellar evolution and is caused by the consumption of fuel and the changing conditions within the star's core. For example, as a star runs out of fuel, it will expand and become a red giant, before eventually shrinking and becoming a white dwarf.

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