Power output of red dwarfs turning yellow and blue?

In summary, the habitable zone of red dwarf stars will migrate outwards as they go from red to yellow, to blue at the end of their lives. This results in additional heat being given off the surface of these stars. The habitable zone also moves outward due to tidal forces, which cause the planets to become tidally locked. The rate of slow down varies depending on the planet's composition and they do not all start with the same rotation rate. The angular momentum lost by the planet is added to its orbit. According to a paper, the habitable zone radius increases with increasing mass, with the final stage being similar to a red giant at 0.25 solar mass and close to solar luminosity between 0.16 and
  • #1
bbbl67
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TL;DR Summary
In latter stages of a red dwarf's life it will start to glow yellow and then eventually blue. What happens to the habitable zones of these objects then?
Although the universe is not old enough to experience these yet, but near the end of the lives of red dwarf stars, they will go from red to yellow, to blue eventually. Does this result in additional heat being given off of the surface of those stars? And if so, then does the habitable zone of these stars migrate outwards, and by how much?

The reason I'm asking is because if the habitable zones of red dwarf stars are currently so nearby that it results in tidally locked planets. So once the red dwarfs become yellow and then blue, will their habitable zones migrate out to locations where the planets that might exist in those locations be non-tidally-locked?
 
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  • #2
Yes the habitable zone moves outward.

The planets have more time for tidal forces to lock the planet. The rate of slow down varies greatly depending on the composition of the planet. Planets do not start with the same rotation rate.
 
  • #3
Wikipedia has the equation for time to tidal lock.

The angular momentum that the planet loses will be added to the orbit.

bbbl67 said:
And if so, then does the habitable zone of these stars migrate outwards, and by how much?
This paper gives you details on how much. The range increases with increasing mass. At 0.25 solar mass the final stage is basically like a red giant. Between 0.16 and 0.2 solar mass the stars end with close to solar luminosity. Increases by several hundred over the luminosity at start of the main sequence.

The radius of the habitable zone increases by the square root of luminosity.
 

1. What causes red dwarfs to turn yellow and blue?

The color of a star is determined by its surface temperature. As red dwarfs age, they begin to fuse heavier elements in their cores, causing their surface temperature to increase and their color to shift from red to yellow and eventually to blue.

2. How does the power output of a red dwarf change as it turns yellow and blue?

The power output of a red dwarf increases as it turns yellow and blue due to the increase in surface temperature. This increase in temperature causes the star to emit more energy and therefore have a higher power output.

3. Can red dwarfs turn back into red stars after turning yellow and blue?

Yes, it is possible for red dwarfs to turn back into red stars. This can occur if the star's fusion reactions slow down or stop, causing its surface temperature to decrease and its color to shift back to red.

4. What is the lifespan of a red dwarf as it turns yellow and blue?

The lifespan of a red dwarf as it turns yellow and blue depends on its initial mass. Generally, the larger the star's mass, the shorter its lifespan. Red dwarfs can live for billions of years as red stars before turning yellow and blue, and their lifespan as yellow and blue stars can vary from a few million to several billion years.

5. How does the power output of a red dwarf compare to other types of stars?

Red dwarfs have a relatively low power output compared to other types of stars, such as main sequence stars like our sun. However, they have a much longer lifespan, allowing them to maintain a steady power output over a longer period of time.

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