<p>From the <a href="https://en.m.wikipedia.org/wiki/Sun" rel="noreferrer">Wikipedia article</a> on the sun, it is about 150 K:</p>
<blockquote>
<p>The Sun is gradually becoming hotter in its core, hotter at the surface, larger in radius, and more luminous during its time on the main sequence: since the beginning of its main sequence life, it has expanded in radius by 15% and the surface has increased in temperature from 5,620 K (5,350 °C; 9,660 °F) to 5,777 K (5,504 °C; 9,939 °F), resulting in a 48% increase in luminosity from 0.677 solar luminosities to its present-day 1.0 solar luminosity.</p>
</blockquote>
<p>That Wikipedia page indirectly sources a paper from the <a href="https://en.wikipedia.org/wiki/Gaia_(spacecraft)" rel="noreferrer">Gaia</a> mission observing sunlike stars which allow verification of these values by comparison with other solar mass stars of different ages: <em><a href="https://doi.org/10.1051/0004-6361/202243800" rel="noreferrer">Gaia Data Release 3: A golden sample of astrophysical parameters</a></em></p>

CC BY-SA 4.0
2023-06-11T15:36:31.640Z
Only covers the main sequence.
ProfRob
CC BY-SA 4.0
2023-06-12T06:25:49.877Z
One should add in that the gradual changes you quote happened of a time period of 4,6 billion years, very gradually indeed.
quarague
CC BY-SA 4.0
2023-06-12T06:52:56.440Z
this raise further questions. how to they know that distant stars are similar to the sun (by mass and age and radius)? how do they know that the temperature was 5620 C? how do they know that luminosity was 0.677? etc
BЈовић
CC BY-SA 4.0
2023-06-12T08:16:03.983Z
@BЈовић these are all perfectly fine questions to ask, but require significantly more space and time to answer than what's afforded in the couple paragraphs that fit in a SO answer.
Cubic
CC BY-SA 4.0
2023-06-12T18:39:19.707Z
@BЈовић: Those are great questions; feel free to post them as top-level questions, linking back to this question, as recommended by ["What is the the best way to ask follow up questions?"](https://meta.stackoverflow.com/questions/266767/what-is-the-the-best-way-to-ask-follow-up-questions) .
David Cary
CC BY-SA 4.0
2023-06-12T23:44:50.393Z
I'll be watching for the follow up questions. I, too, wonder how a time sequence for the Sun can be created when the only parameters that don't change with time (not much anyway) are mass and composition, with mass being hard (to say the least) to directly measure. I believe that our current estimates have just been from modeling.
Jack R. Woods
CC BY-SA 4.0
2023-06-11T00:36:10.747Z
2023-06-11T14:36:38.557Z
2023-06-11T14:36:38.557Z
planetmaker
<p>I am constantly reading that the Sun is at least 20% 'hotter', in terms of total radiation/luminosity, than it was a few million years after its formation (i.e., after the <a href="https://en.wikipedia.org/wiki/Hayashi_track" rel="noreferrer">Hayashi stage</a>...)</p>
<p>But what about its absolute temperature?  I know that it hasn't changed as much, but has it increased (or decreased) at all?</p>

CC BY-SA 4.0
2023-06-11T00:22:38.193Z
Let's hope your sources say, that the sun is 20% brighter, not hotter. 20% of the temperature would be a whopping 1000K
planetmaker
CC BY-SA 4.0
2023-06-11T15:36:44.303Z
See https://astronomy.stackexchange.com/questions/14535/why-is-the-suns-brightness-and-radius-increasing-but-not-its-temperature
ProfRob
CC BY-SA 4.0
2023-06-12T15:19:43.513Z
The sun is a near-perfect (at the scales we are talking about) black body radiator.  Power per square meter is the 4th power of temperature.  If the sun is brighter, it must be either larger or hotter.
Yakk - Adam Nevraumont
CC BY-SA 4.0
2023-08-09T13:22:19.393Z
Two out of three answers were plagiarised (now deleted). Don't they have any shame?
Peter Mortensen
<the-sun><astrophysics><history><temperature><stellar-astrophysics>
Is the Sun hotter today, in terms of absolute temperature (i.e., NOT total luminosity), than it was in the distant past?
Kurt Hikes
# Is the Sun hotter today, in terms of absolute temperature (i.e., NOT total luminosity), than it was in the distant past?

(Asked by: username_0 on 2023-06-11)

I am constantly reading that the Sun is at least 20% 'hotter', in terms of total radiation/luminosity, than it was a few million years after its formation (i.e., after the [Hayashi stage](https://en.wikipedia.org/wiki/Hayashi_track)...)

But what about its absolute temperature? I know that it hasn't changed as much, but has it increased (or decreased) at all?

**Tags:** the-sun, astrophysics, history, temperature, stellar-astrophysics
> **Comments:**
> **username_1**: Let's hope your sources say, that the sun is 20% brighter, not hotter. 20% of the temperature would be a whopping 1000K  
> **username_2**: See https://astronomy.stackexchange.com/questions/14535/why-is-the-suns-brightness-and-radius-increasing-but-not-its-temperature  
> **username_3**: The sun is a near-perfect (at the scales we are talking about) black body radiator.  Power per square meter is the 4th power of temperature.  If the sun is brighter, it must be either larger or hotter.  
> **username_4**: Two out of three answers were plagiarised (now deleted). Don't they have any shame?  

---

## 1 answers

### Answer by username_1 on 2023-06-11. Score: 16

From the [Wikipedia article](https://en.m.wikipedia.org/wiki/Sun) on the sun, it is about 150 K:

> The Sun is gradually becoming hotter in its core, hotter at the surface, larger in radius, and more luminous during its time on the main sequence: since the beginning of its main sequence life, it has expanded in radius by 15% and the surface has increased in temperature from 5,620 K (5,350 °C; 9,660 °F) to 5,777 K (5,504 °C; 9,939 °F), resulting in a 48% increase in luminosity from 0.677 solar luminosities to its present-day 1.0 solar luminosity.

That Wikipedia page indirectly sources a paper from the [Gaia](https://en.wikipedia.org/wiki/Gaia_(spacecraft)) mission observing sunlike stars which allow verification of these values by comparison with other solar mass stars of different ages: *[Gaia Data Release 3: A golden sample of astrophysical parameters](https://doi.org/10.1051/0004-6361/202243800)*

> **Comments:**
> **username_2**: Only covers the main sequence.  
> **username_5**: One should add in that the gradual changes you quote happened of a time period of 4,6 billion years, very gradually indeed.  
> **username_6**: this raise further questions. how to they know that distant stars are similar to the sun (by mass and age and radius)? how do they know that the temperature was 5620 C? how do they know that luminosity was 0.677? etc  
> **username_7**: @BЈовић these are all perfectly fine questions to ask, but require significantly more space and time to answer than what's afforded in the couple paragraphs that fit in a SO answer.  
> **username_8**: @BЈовић: Those are great questions; feel free to post them as top-level questions, linking back to this question, as recommended by ["What is the the best way to ask follow up questions?"](https://meta.stackoverflow.com/questions/266767/what-is-the-the-best-way-to-ask-follow-up-questions) .  
> **username_9**: I'll be watching for the follow up questions. I, too, wonder how a time sequence for the Sun can be created when the only parameters that don't change with time (not much anyway) are mass and composition, with mass being hard (to say the least) to directly measure. I believe that our current estimates have just been from modeling.  

---

