# Mass of the sun

## Main Question or Discussion Point

How much mass does the sun lose every year?

## Answers and Replies

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How much mass does the sun lose every year?
Can you be more precise ? It is not difficult to estimate how much energy goes away in the form of light, and that is easy to convert into mass terms, but the sun also looses mass by other processes, less under control and more difficult to estimate.

A close an estimate as possible. I heard it was a tonne a second, it did'nt sound right.

Astronuc
Staff Emeritus
The sun apparently loses mass at a rate of 1.9 x 109 kg/s, or about 3 x 10-14 of it's total mass (1.981 x 1030) each year.

http://farside.ph.utexas.edu/teaching/plasma/lectures/node68.html

http://solarphysics.livingreviews.org/Articles/lrsp-2004-2/articlesu7.html#x15-1200114

Here is a different estimate -
Plugging this into the above formula tells us that the Sun loses around 4,200,000,000 kilograms every second!
http://curious.astro.cornell.edu/question.php?number=563 [Broken]

Here is an earlier discussion at PF -

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Does the statement that the Sun is losing mass mean that it is losing the content of Hydrogen and Helium in it? I mean, isn't Hydrogen and Helium what makes up the Sun's mass?
I mean since the Sun makes up the maaaajor (major,I mean,Just to indicate the vastness of its majority) part of the Solar system's mass, is the Sun's loss of mass going to affect us in any way? Forgive me if its a dumb question.

malawi_glenn
Homework Helper
yes if the sun looses mass, the radii of the planets orbits will be slightly changed. But there is no danger. When the sun blows up to become a red giant, however, things can happen ;-)

But this is astrophysics, not nuclear physics.

Astronuc
Staff Emeritus
Does the statement that the Sun is losing mass mean that it is losing the content of Hydrogen and Helium in it? I mean, isn't Hydrogen and Helium what makes up the Sun's mass?
I mean since the Sun makes up the maaaajor (major,I mean,Just to indicate the vastness of its majority) part of the Solar system's mass, is the Sun's loss of mass going to affect us in any way? Forgive me if its a dumb question.
Here is one scenario for the sun's evolution - http://www.astronomy.ohio-state.edu/~pogge/Ast162/Unit6/futuresun.html

Scroll to Mid-Life Crisis for the Earth or 5.6 Gyr (~1.1 Gyr from now).

The sun loses about 3-6.3 x 10-14 of its mass each year so the change in mass is neglible on an annual basis. Even over the remainder of the sun's life that amount to =<0.00032 solar mass.

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Kurdt
Staff Emeritus
Gold Member
There are two ways the sun loses mass. The conversion of hydrogen to higher elements and through the solar wind. Since this was posted in nuclear first I would think you were after the mass loss through nuclear fusion. Thats relatively easy to estimate since the energy emitted from the sun in radiation must have come from those fusion processes. The figure of 4.2 billion kg given by Astro earlier is a good estimate of the mass loss from nuclear reactions.

yes if the sun looses mass, the radii of the planets orbits will be slightly changed. But there is no danger. When the sun blows up to become a red giant, however, things can happen ;-).
Sorry, I could not see the emot-icon!Could you please tell me what things can happen?

But this is astrophysics, not nuclear physics.
Yes, I knew it, but since I was not the one who started this thread I could do nothing.

I am completely knew to this topic so please don't mind when I ask that, when Kurdt says that"The figure of 4.2 billion kg given by Astro earlier is a good estimate of the mass loss from nuclear reactions" what are those nuclear reactions exactly and how are they caused and what do they do to make the sun loss its mass?

Kurdt
Staff Emeritus
Gold Member
The main reaction in the sun is something called the proton-proton chain where essentially 4 protons fuse together to make a helium atom through a number of steps. Here is an overview but there are loads more you may like better by googling.

http://csep10.phys.utk.edu/astr162/lect/energy/ppchain.html

We know that helium has less mass than the four protons that went into making it so we have energy at the end of this reaction. We know from a little known physicist called Albert Einstein that mass can be converted into energy from the following equation:

$$E=mc^2$$

This extra energy is radiated away as light. The reactions are caused by the immense pressure and temperature in the suns core due to compression under its own gravity. The temperature in the suns core is ~ 15 million Kelvin.

Amazing!I still have a question? Do you think that if the heat slowly reduces in the sun the reaction will slow down and the sun will not lose as much mass? Helium is formed by four protons fusing but what about hydrogen?How is hydrogen present in the sun?I also read that around 75% of the sun consists of hydrogen.What impact does hydrogen throw on the Sun? Does is also fuse and is less heavier than what made it and contribute to the sun's loss of mass or does it do something else?Awesome explanation!Thanks!

Janus
Staff Emeritus