Oldest solar twin identified: VLT provides new clues to help solve lithium mystery

Aug 28, 2013
This image tracks the life of a Sun-like star, from its birth on the left side of the frame to its evolution into a red giant star on the right. On the left the star is seen as a protostar, embedded within a dusty disc of material as it forms. It later becomes a star like our Sun. After spending the majority of its life in this stage, the star's core begins to gradually heat up, the star expands and becomes redder until it transforms into a red giant. Following this stage, the star will push its outer layers into the surrounding space to form an object known as a planetary nebula, while the core of the star itself will cool into a small, dense remnant called a white dwarf star. Marked on the lower timeline are where our Sun and solar twins 18 Sco and HIP 102152 are in this life cycle. The Sun is 4.6 billion years old and 18 Sco is 2.9 billion years old, while the oldest solar twin is some 8.2 billion years old -- the oldest solar twin ever identified. By studying HIP 102152, we can get a glimpse of what the future holds for our Sun. This image is illustrative; the ages, sizes, and colours are approximate (not to scale). The protostar stage, on the far left of this image, can be some 2000 times larger than our Sun. The red giant stage, on the far right of this image, can be some 100 times larger than the Sun. Credit: ESO/M. Kornmesser

(Phys.org) —An international team led by astronomers in Brazil has used ESO's Very Large Telescope to identify and study the oldest solar twin known to date. Located 250 light-years from Earth, the star HIP 102152 is more like the Sun than any other solar twin—except that it is nearly four billion years older. This older, but almost identical, twin gives us an unprecedented chance to see how the Sun will look when it ages. The new observations also provide an important first clear link between a star's age and its lithium content, and in addition suggest that HIP 102152 may be host to rocky terrestrial planets.

Astronomers have only been observing the Sun with telescopes for 400 years—a tiny fraction of the Sun's age of 4.6 billion years. It is very hard to study the history and future evolution of our star, but we can do this by hunting for rare stars that are almost exactly like our own, but at different stages of their lives. Now astronomers have identified a star that is essentially an identical twin to our Sun, but 4 billion years older—almost like seeing a real version of the in action.

Jorge Melendez (Universidade de São Paulo, Brazil), the leader of the team and co-author of the new paper explains: "For decades, astronomers have been searching for solar twins in order to know our own life-giving Sun better. But very few have been found since the first one was discovered in 1997. We have now obtained superb-quality spectra from the VLT and can scrutinise solar twins with , to answer the question of whether the Sun is special."

The team studied two solar twins—one that was thought to be younger than the Sun (18 Scorpii) and one that was expected to be older (HIP 102152). They used the UVES on the Very Large Telescope (VLT) at ESO's Paranal Observatory to split up the light into its component colours so that the chemical composition and other properties of these stars could be studied in great detail.

They found that HIP 102152 in the constellation of Capricornus (The Sea Goat) is the oldest solar twin known to date. It is estimated to be 8.2 billion years old, compared to 4.6 billion years for our own Sun. On the other hand 18 Scorpii was confirmed to be younger than the Sun—about 2.9 billion years old.

This video is not supported by your browser at this time.
This 3D animation shows the life of a Sun-like star, from its birth on the left side of the frame to its evolution into a red giant star on the right. On the left the star is seen as a protostar, embedded within a dusty disc of material as it forms. It later becomes a star like our Sun. After spending the majority of its life in this stage, the star transforms into a red giant. Following this stage, the star will push its outer layers into the surrounding space to form an object known as a planetary nebula, while the core of the star itself will cool into a small, dense remnant called a white dwarf star. Marked on the lower timeline are where our Sun and solar twins 18 Sco and HIP 102152 are in this life cycle. The Sun is 4.6 billion years old and 18 Sco is 2.9 billion years old, while the oldest solar twin is some 8.2 billion years old — the oldest solar twin ever identified. By studying HIP 102152, we can get a glimpse of what the future holds for our Sun. This animation is illustrative; the ages, sizes, and colours are approximate (not to scale). The protostar stage can be some 2000 times larger than our Sun. The red giant stage can be some 100 times larger than the Sun. Credit: ESO/M. Kornmesser

Studying the ancient solar twin HIP 102152 allows scientists to predict what may happen to our own Sun when it reaches that age, and they have already made one significant discovery. "One issue we wanted to address is whether or not the Sun is typical in composition," says Melendez. "Most importantly, why does it have such a strangely low lithium content?"

Lithium, the third element in the periodic table, was created in the Big Bang along with hydrogen and helium. Astronomers have pondered for years over why some stars appear to have less lithium than others. With the new observations of HIP 102152, have taken a big step towards solving this mystery by pinning down a strong correlation between a Sun-like star's age and its lithium content.

Our own Sun now has just 1% of the lithium content that was present in the material from which it formed. Examinations of younger solar twins have hinted that these younger siblings contain significantly larger amounts of lithium, but up to now scientists could not prove a clear correlation between age and lithium content.

TalaWanda Monroe (Universidade de São Paulo), the lead author on the new paper, concludes: "We have found that HIP 102152 has very low levels of lithium. This demonstrates clearly for the first time that older solar twins do indeed have less lithium than our own Sun or younger solar twins. We can now be certain that stars somehow destroy their lithium as they age, and that the Sun's content appears to be normal for its age."

A final twist in the story is that HIP 102152 has an unusual pattern that is subtly different to most other solar twins, but similar to the Sun. They both show a deficiency of the elements that are abundant in meteorites and on Earth. This is a strong hint that HIP 102152 may host terrestrial rocky planets.

Explore further: Fermi finds a 'transformer' pulsar

More information: This research was presented in a paper to appear in "High precision abundances of the old solar twin HIP 102152: insights on Li depletion from the oldest Sun", by TalaWanda Monroe et al. in the Astrophysical Journal Letters. Research paper PDF

Related Stories

Exoplanets Clue to Sun's Curious Chemistry

Nov 11, 2009

(PhysOrg.com) -- A ground-breaking census of 500 stars, 70 of which are known to host planets, has successfully linked the long-standing "lithium mystery" observed in the Sun to the presence of planetary systems. ...

Solar System genealogy revealed by meteorites

Aug 29, 2012

(Phys.org)—The stellar environment of our Solar System at its birth is poorly known, as it has accomplished some twenty revolutions around the Galactic centre since its formation 4.5 billion years ago. ...

Scientists discover ageing star destroys planet

Sep 21, 2012

(Phys.org)—An international team of astronomers has found evidence that a planet was destroyed by its ageing star. Led by Pennsylvania State University (Penn State) in the United States, the team showed ...

Earth-sized planet found just outside solar system

Oct 16, 2012

(Phys.org)—European astronomers have discovered a planet with about the mass of the Earth orbiting a star in the Alpha Centauri system—the nearest to Earth. It is also the lightest exoplanet ever discovered ...

The star that should not exist

Aug 31, 2011

(PhysOrg.com) -- A team of European astronomers has used ESO’s Very Large Telescope (VLT) to track down a star in the Milky Way that many thought was impossible. They discovered that this star is composed ...

Recommended for you

Lives and deaths of sibling stars

7 hours ago

This beautiful star cluster, NGC 3293, is found 8000 light-years from Earth in the constellation of Carina (The Keel). This cluster was first spotted by the French astronomer Nicolas-Louis de Lacaille in ...

Fermi finds a 'transformer' pulsar

Jul 22, 2014

(Phys.org) —In late June 2013, an exceptional binary containing a rapidly spinning neutron star underwent a dramatic change in behavior never before observed. The pulsar's radio beacon vanished, while at ...

User comments : 12

Adjust slider to filter visible comments by rank

Display comments: newest first

katesisco
1 / 5 (9) Aug 28, 2013
Very low isn't much info --if the star that is twice as old as the sun has any lithium at all that would be surprising wouldn't it?
hemitite
1 / 5 (1) Aug 28, 2013
I would guess that the first place to look for mechanisms of lithium depletion in older stars is in the stellar wind (where the answer is blowing).
Q-Star
3 / 5 (6) Aug 28, 2013
Very low isn't much info --if the star that is twice as old as the sun has any lithium at all that would be surprising wouldn't it?


Uuuuh, no, since most of the lithium in universe today was created in the minutes just after the big bang. What is mysterious is that any star or object would have more OR less lithium than any other. The abundance of hydrogen is pretty much the same where ever ya look, within one percent or so. Same with helium. It should be so with lithium.
Urgelt
5 / 5 (3) Aug 29, 2013
Q-Star wrote, "The abundance of hydrogen is pretty much the same where ever ya look, within one percent or so. Same with helium. It should be so with lithium."

Not exactly. If you look at aged main sequence stars, they're hydrogen-depleted and helium-enriched. They have to be; they've fused a substantial portion of their hydrogen.

The result cited by the article suggests that Lithium may also be fused in main-sequence stars, though of course there's much less Lithium to start with than hydrogen, and we don't know the fusion pathways involved. It ought to be possible to figure it out, though, given the improvements in spectrometry now being applied to the problem.

Who knew? Not me. I had no idea that lithium might be fused in main-sequence stars. I'd expect it in more energetic scenarios such as novas, but main-sequence stars? It's a pretty cool possibility. It suggests that there's more going on inside a conventional sun-like star than we had thus far guessed.
IMP-9
3.6 / 5 (8) Aug 29, 2013
Big bang was proposed long before inflation and does not include a singularity (neither does standard cosmology). And no, observations of distant galaxies are not at conflict with the primordial and stellar nucleosynthesis. Don't confuse quantitative science with your nonsense Zephyr.
IMP-9
5 / 5 (2) Aug 29, 2013
Should read : "Big bang nucleosynthesis was proposed..."
IMP-9
5 / 5 (4) Aug 29, 2013
It does include "primordial atom", as Lemaître named it.

That was a typo, you can see that. The primordial singularity is not part of standard cosmology today. Hot and dense does not mean singularity at all. It does not defy current physics because current physics cannot describe such a high energy environment.

Or even better "nucleosynthesis was proposed", because the author of this nucleosynthesis Fred Hoyle was a pungent opponent of Big Bang cosmology as such.

No, you've intentionally misquoted me. Big bang nucleosynthesis was not proposed by Hoyle but by Alpher and Gamow. Hoyle's opinions are irrelevant.
Q-Star
3.7 / 5 (3) Aug 29, 2013
If something looks like a duck, swims like a duck, and quacks like a duck, it is a duck


Aaah, Zephyr,,, there ya are sure, and looking so like yourself. I've missed the ducks, thanks for bringing them back. But ya left out the part about them paddling as electrons on the surface ripples of longitudinal waves and emitting transverse photons with every quack. Did ya forget that one?

It was one of my favorites,,,, please do the "electron ducks" skit again.

@ All ya newcomers, Zephyr's "electron ducks" is one of his classics and not to be missed. It was much funnier than his "water walking spider surfing on the surface of rippling water waves".
Q-Star
4 / 5 (4) Aug 29, 2013
Q-Star wrote, "The abundance of hydrogen is pretty much the same where ever ya look, within one percent or so. Same with helium. It should be so with lithium."

Not exactly. If you look at aged main sequence stars, they're hydrogen-depleted and helium-enriched. They have to be; they've fused a substantial portion of their hydrogen.


You are entirely correct, I was over generalizing the situation and can see where I might have led to a misunderstanding if someone couldn't read my mind. I should have made "overall" more predominant in my remark,,,,

Good catch, thank ya.
rug
1 / 5 (3) Aug 29, 2013
The result cited by the article suggests that Lithium may also be fused in main-sequence stars, though of course there's much less Lithium to start with than hydrogen, and we don't know the fusion pathways involved.


Here is a hypothesis, maybe the lithium is needed to get the fusion process started in these smaller stars. Maybe lithium will help us get fusion going here in lab experiments.
Fleetfoot
5 / 5 (2) Sep 03, 2013
since most of the lithium in universe today was created in the minutes just after the big bang
This is just a theory full of ad-hoced unphysical stuffs ..


No, BBNS is calculated from the properties of nuclear interactions which have been observed and acurately measured in the lab. The predicted mix is within a fraction of a percent of what is seen.

That lithium is slowly destroyed in main sequence stars has been known for a long time:

"The observed lithium abundance in stars is less than the predicted lithium abundance, by a factor of about 2. But stars destroy lithium so it is hard to assess the significance of this difference."

http://www.astro....BNS.html

There was also an article earlier this year noting that the measured values were slightly incorrect which pretty much resolved that "problem":

http://phys.org/n...ory.html
Fleetfoot
5 / 5 (1) Sep 06, 2013
In brief, the fact that the nuclesynthesis can be described with using of our models of nuclear interactions doesn't imply anything about its general scope, i.e. about cosmological models. It's just fitting of the observations at the nuclear scale to the observations at the cosmic scales - no less, no more.


What gives us confidence though it is that there is only one parameter which can be adjusted, everything else comes from the lab measurements. That factor is the photon/baryon ratio but we have multiple different tests of the prediction. The fact that a single value fits all the measurements very well would be a remarkable coincidence if the model were wrong.