# B In how many years will the surface of the Sun be 75 degrees Fahrenheit?

1. Feb 13, 2017

### lifeonmercury

Eventually the Sun will go through its phases and cool down. Is it possible to calculate how long it will take for the surface to cool to 75 degrees Fahrenheit?

2. Feb 13, 2017

### Aizen

Well when our sun's surface does cool to 75 degrees fahrenheit it will be considered a black dwarf as it will not be radiating enough heat and light to be considered a white dwarf, now the current length of time it takes for a white dwarf to cool to a black dwarf is calculated to be longer than the age of the universe itself.

While i can not give you an exact time i can however assure you this process will take over 14 billion years, and over 20 billion years if you are counting the time it will take for the sun to become a red giant and then turn into a white dwarf.

I am also unsure of the time period it takes for a white dwarf to cool to a black dwarf, maybe one of our lovely mentors or science advisors can give you an idea for how long it would take.

Last edited: Feb 13, 2017
3. Feb 13, 2017

### rootone

I can't remember a figure for this, but yes a white dwarf cooling to a black dwarf would take a very long time.
The cooler it gets the less it radiates until it's taking millions, even billions of years to cool by 1 more degree.
I can recall somebody who did math on this coming up with the conclusion that so far, no black dwarf can exist.
The universe isn't old enough yet.

4. Feb 13, 2017

### maroubrabeach

Yes, that's the way I also understand it. A White Dwarf would need more than the lifetime of the universe to finally reach a black dwarf or cinder stage, and that is evident in the fact that as yet we have never seen one nor have any evidence of them as yet.

5. Feb 14, 2017

### lifeonmercury

After looking even further into the matter, I found this link about the Timeline of the Far Future.

1015 (1 quadrillion years): Estimated time until stellar close encounters detach all planets in star systems (including the Solar System) from their orbits. By this point, the Sun will have cooled to five degrees above absolute zero.