<blockquote>
  <p>Later estimates shows that the star could be as old as 14.5 billion years (± 0.8 billion years), which is still it older than the universe's calculated age of about 13.8 billion years, an obvious dilemma.</p>
</blockquote>

<p>There is no dilemma. That ± 0.8 billion years is important. Subtract 0.8 billion years from that 14.5 billion year figure (<a href="http://iopscience.iop.org/article/10.1088/0004-637X/792/2/110/meta" rel="noreferrer">later revised to 14.27 billion years</a>) and you get 13.7 billion years, less than the age of the universe. Also note that that 0.8 billion years uncertainty is the standard error, or roughly one standard deviation. That revised age of 14.27 billion years makes the dilemma essentially non-existent. That's older than the estimate age of the universe by 0.4 to 0.5 million years, and this is not significant even at the one sigma level.</p>

<p>Particle physicists generally use the five sigma level as distinguishing between "almost certain" and "maybe" (and particle physicists are reluctant to publish "maybes"). Astronomers generally use a three sigma level. Even social scientists would balk at a deviation that is less than one sigma as being significant.</p>

CC BY-SA 3.0
2016-12-20T15:16:12.863Z
You say that "astronomers generally use a three sigma level" but also say that the "0.8 billion years uncertainty is ... roughly one standard deviation". That 0.8 Gyr number comes from [this paper](http://iopscience.iop.org/article/10.1088/2041-8205/765/1/L12/meta), so ... is that one standard deviation or three?
dcsohl
CC BY-SA 3.0
2017-01-06T22:44:16.537Z
Usually astronomers quote 1 sigma errors, so David is saying a 2 or 3 sigma deviation is not uncommon.  Also, astronomers often leave off systematic errors because they usually do not know just how big they are.  Are all stellar ages off because we have left out something in the theory of stars?  For instance, effects of high rotation or strong internal magnetic fields, etc. Same for the age of the universe.
eshaya
CC BY-SA 3.0
2016-12-19T12:00:21.817Z
2016-12-19T17:11:06.783Z
2016-12-19T17:11:06.783Z
David Hammen
<p>The most recent age estimates for this stars using improved interferometric estimations of angular diameter (to better estimate the effective temperature) and more sophisticated stellar models are:</p>
<p><span class="math-container">$13.7 \pm 0.7$</span> Gyr or <span class="math-container">$12.2 \pm 0.6$</span> Gyr, depending on the adopted extinction (<a href="https://arxiv.org/abs/1410.4780" rel="nofollow noreferrer">Creevey et al. 2017</a>).</p>
<p><span class="math-container">$12.5 - 14.9$</span> Gyr, depending on the exact stellar parameters adopted and the convective mixing length used in the models (<a href="https://arxiv.org/abs/1712.05082" rel="nofollow noreferrer">Joyce &amp; Chaboyer 2018</a>).</p>
<p><span class="math-container">$12 \pm 0.5$</span> Gyr (<a href="https://iopscience.iop.org/article/10.3847/2515-5172/ac01ca/meta" rel="nofollow noreferrer">Tang &amp; Joyce 2021</a>).</p>
<p>Looking at these results, there is no strong evidence that this star is older than the age of the universe derived from the analysis of the cosmic microwave background of 13.7 Gyr. The derived age is still highly sensitive at the 1 Gyr level to changes in the assumed extinction of the star by <span class="math-container">$\pm 0.1$</span> mag and by relatively small changes in the convective mixing length adopted (used to in estimating the heat flux out of the star).</p>

CC BY-SA 4.0
2023-11-03T17:19:37.527Z
2023-11-03T17:19:37.527Z
ProfRob
<p>Scientists have known about the star <em>HD 140283</em>, informally nicknamed the Methuselah star, for more than 100 years, since it cruises across the sky at a relatively rapid clip. The star moves at about 800,000 mph (1.3 million km/h) and travels the width of the full moon in the sky every 1,500 years or so, researchers said. Its apparent magnitude is 7.223.</p>

<p><a href="http://www.space.com/20112-oldest-known-star-universe.html" rel="noreferrer">Previous research</a> had estimated that the Milky Way galaxy's so-called
"Methuselah star" is up to <strong>16 billion years old</strong>. That's a problem,
since most researchers agree that the Big Bang that created the
universe occurred about <strong>13.8 billion years ago</strong>.</p>

<p><a href="https://www.nasa.gov/mission_pages/hubble/science/hd140283.html" rel="noreferrer">Later estimates</a> show that the star could be as old as <strong>14.5 billion years</strong> (± 0.8 billion years), which is still it older than the universe's calculated age of about <strong>13.8 billion years</strong>. This is an obvious dilemma.</p>

<p><strong>How can a star be older than the universe itself?</strong></p>

CC BY-SA 3.0
2016-12-19T17:43:22.217Z
Just to clarify, it's obviously not older than the universe. Rather, one or both of our estimates are off, as is discussed in the answers below.
Leliel
CC BY-SA 3.0
2016-12-19T20:29:25.880Z
A very good question. If you look at the "age of universe" entry in wikipedia, it also mentions that those "older than universe" stars were a real bad problem for the finite age universe models. If further refinements in either the star/universe age occur in future, it is very possible that this problem is resurrecting again and the current models are invalidated.
Thorsten S.
CC BY-SA 3.0
2016-12-20T04:08:22.433Z
It seems to me (though I'm not an expert on how stellar age is determined), but if a star loses mass, perhaps by orbiting a white dwarf that star would appear older than it is, and the opposite, if a star accrues mass, it will appear younger than it really is.    A star that orbits a white dwarf, loses mass to it and, that white dwarf goes nova, might explain a star that appears older than the universe, but, just speculating.
userLTK
CC BY-SA 3.0
2016-12-20T04:21:46.220Z
Related question: [Age of the universe versus its contents](http://astronomy.stackexchange.com/questions/11050/age-of-the-universe-vs-its-contents).
joeytwiddle
CC BY-SA 3.0
2017-01-11T13:00:19.857Z
[Very similar question on Physics.SE.](http://physics.stackexchange.com/questions/73928/what-could-explain-the-measurements-that-the-methuselah-star-is-older-than-the-u)
Warrick
<star><universe>
How can 'HD 140283' be older than the universe?
Mohammad Zain Abbas
# How can 'HD 140283' be older than the universe?

(Asked by: username_0 on 2016-12-19)

Scientists have known about the star *HD 140283*, informally nicknamed the Methuselah star, for more than 100 years, since it cruises across the sky at a relatively rapid clip. The star moves at about 800,000 mph (1.3 million km/h) and travels the width of the full moon in the sky every 1,500 years or so, researchers said. Its apparent magnitude is 7.223.

[Previous research](http://www.space.com/20112-oldest-known-star-universe.html) had estimated that the Milky Way galaxy's so-called
"Methuselah star" is up to **16 billion years old**. That's a problem,
since most researchers agree that the Big Bang that created the
universe occurred about **13.8 billion years ago**.

[Later estimates](https://www.nasa.gov/mission_pages/hubble/science/hd140283.html) show that the star could be as old as **14.5 billion years** (± 0.8 billion years), which is still it older than the universe's calculated age of about **13.8 billion years**. This is an obvious dilemma.

**How can a star be older than the universe itself?**

**Tags:** star, universe

> **Comments:**
> **username_1**: Just to clarify, it's obviously not older than the universe. Rather, one or both of our estimates are off, as is discussed in the answers below.  
> **username_2**: A very good question. If you look at the "age of universe" entry in wikipedia, it also mentions that those "older than universe" stars were a real bad problem for the finite age universe models. If further refinements in either the star/universe age occur in future, it is very possible that this problem is resurrecting again and the current models are invalidated.  
> **username_3**: It seems to me (though I'm not an expert on how stellar age is determined), but if a star loses mass, perhaps by orbiting a white dwarf that star would appear older than it is, and the opposite, if a star accrues mass, it will appear younger than it really is.    A star that orbits a white dwarf, loses mass to it and, that white dwarf goes nova, might explain a star that appears older than the universe, but, just speculating.  
> **username_4**: Related question: [Age of the universe versus its contents](http://astronomy.stackexchange.com/questions/11050/age-of-the-universe-vs-its-contents).  
> **username_5**: [Very similar question on Physics.SE.](http://physics.stackexchange.com/questions/73928/what-could-explain-the-measurements-that-the-methuselah-star-is-older-than-the-u)  

---

## 2 answers

### Answer by username_6 on 2016-12-19. Score: 17

> Later estimates shows that the star could be as old as 14.5 billion years (± 0.8 billion years), which is still it older than the universe's calculated age of about 13.8 billion years, an obvious dilemma.

There is no dilemma. That ± 0.8 billion years is important. Subtract 0.8 billion years from that 14.5 billion year figure ([later revised to 14.27 billion years](http://iopscience.iop.org/article/10.1088/0004-637X/792/2/110/meta)) and you get 13.7 billion years, less than the age of the universe. Also note that that 0.8 billion years uncertainty is the standard error, or roughly one standard deviation. That revised age of 14.27 billion years makes the dilemma essentially non-existent. That's older than the estimate age of the universe by 0.4 to 0.5 million years, and this is not significant even at the one sigma level.

Particle physicists generally use the five sigma level as distinguishing between "almost certain" and "maybe" (and particle physicists are reluctant to publish "maybes"). Astronomers generally use a three sigma level. Even social scientists would balk at a deviation that is less than one sigma as being significant.

> **Comments:**
> **username_7**: You say that "astronomers generally use a three sigma level" but also say that the "0.8 billion years uncertainty is ... roughly one standard deviation". That 0.8 Gyr number comes from [this paper](http://iopscience.iop.org/article/10.1088/2041-8205/765/1/L12/meta), so ... is that one standard deviation or three?  
> **username_8**: Usually astronomers quote 1 sigma errors, so username_6 is saying a 2 or 3 sigma deviation is not uncommon.  Also, astronomers often leave off systematic errors because they usually do not know just how big they are.  Are all stellar ages off because we have left out something in the theory of stars?  For instance, effects of high rotation or strong internal magnetic fields, etc. Same for the age of the universe.  

---

### Answer by username_9 on 2023-11-03. Score: 2

The most recent age estimates for this stars using improved interferometric estimations of angular diameter (to better estimate the effective temperature) and more sophisticated stellar models are:

$13.7 \pm 0.7$ Gyr or $12.2 \pm 0.6$ Gyr, depending on the adopted extinction ([Creevey et al. 2017](https://arxiv.org/abs/1410.4780)).

$12.5 - 14.9$ Gyr, depending on the exact stellar parameters adopted and the convective mixing length used in the models ([Joyce & Chaboyer 2018](https://arxiv.org/abs/1712.05082)).

$12 \pm 0.5$ Gyr ([Tang & Joyce 2021](https://iopscience.iop.org/article/10.3847/2515-5172/ac01ca/meta)).

Looking at these results, there is no strong evidence that this star is older than the age of the universe derived from the analysis of the cosmic microwave background of 13.7 Gyr. The derived age is still highly sensitive at the 1 Gyr level to changes in the assumed extinction of the star by $\pm 0.1$ mag and by relatively small changes in the convective mixing length adopted (used to in estimating the heat flux out of the star).


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