New ideas add further mystery to why there is less lithium-7 in the universe than expected

Jul 20, 2012 by Bob Yirka report
This artist's concept shows a galaxy with a supermassive black hole at its core. The black hole is shooting out jets of radio waves. Image credit: NASA/JPL-Caltech

(Phys.org) -- Thirty years ago, cosmologists Monique and François Spite of the Paris Observatory, turned the world of astrophysics upside down when they noticed that there appeared to be a distinct lack of lithium-7 in old stars in the halo of the Milky Way, which led to questions about why there wasn’t more as expected by theories about the Big Bang. Since then, more research has shown that lithium-7 simply refuses to conform to models and theories about how the universe began; there’s just not enough of it. Now, things have grown worse as researchers Fabio Iocco and Miguel Pato from Stockholm University and Technische Universität in Munich, have published a study in Physical Review Letters describing what they believe is lithium-7 production by certain black holes.

Current theory holds that some fourteen billion years ago, the Big Bang occurred and everything we know came about as a result. In those first few moments afterwards, elements were formed and persist to this day. Modeling of the Big Bang has found that all of the elements in existence conform to theories suggesting how much of each should exist. Except for -7. For some reason, there is approximately just a third of what there should be and astrophysicists don’t know why. Now, new research suggests that there should be even more, maybe twice what was originally thought.

Iocco and Pato, in looking at x-ray sources that come from binary star arrangements that are thought to harbor , have found what appears to be torus shaped matter (from one of the stars) swirling around and towards the gravity source. In doing the math, they calculate that the matter nears the speed at which light travels as it approaches, reaching temperatures of 100 billion K. Under those conditions, the duo suspect that helium nuclei colliding could result in the creation of lithium-7, which if true would mean that there is even more of the stuff missing than researchers had first thought. They write that if something on the order of 1% of such systems are producing helium-7, the amount of it produced would equal as much as is believed to have been created after the Big Bang.

Astrophysicists have suggested a lot of theories to explain the dearth of helium-7, but thus far, none have panned out, and none of them are proposing that the original ideas used to describe how much there should be, are wrong.

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More information: Lithium Synthesis in Microquasar Accretion, Phys. Rev. Lett. 109, 021102 (2012). DOI:10.1103/PhysRevLett.109.021102 (Arxiv pre-print: http://arxiv.org/abs/1206.0736 )

Abstract
We study the synthesis of lithium isotopes in the hot tori formed around stellar mass black holes by accretion of the companion star. We find that sizable amounts of both stable isotopes 6Li and 7Li can be produced, the exact figures varying with the characteristics of the torus and reaching as much as 10-2M⊙ for each isotope. This mass output is enough to contaminate the entire Galaxy at a level comparable with the original, pregalactic amount of lithium and to overcome other sources such as cosmic-ray spallation or stellar nucleosynthesis.

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wealthychef
3.5 / 5 (2) Jul 20, 2012
Where did they come up with the "order of 1%" figure of the number of lithium-producing systems? That sounds suspiciously pulled out of a hat.
Satene
2.1 / 5 (7) Jul 20, 2012
The missing lithium problem of Big Bang theory is symmetric to the abundance of heavy elements (like the tellurium) found inside of distant stars and galaxies. These elements shouldn't be there, if we consider, only lightweight elements were formed after Big bang and their production in stars takes time ( 1,2,3,4,5,6,..)
danlgarmstrong
3.9 / 5 (7) Jul 20, 2012
Lithium 7 must be pretty useful stuff. The ONLY possible explanation is that ET civilizations are all scooping the stuff up.
Parsec
5 / 5 (5) Jul 20, 2012
The missing lithium problem of Big Bang theory is symmetric to the abundance of heavy elements (like the http://phys.org/n...html,..)

Estimates of star formation and their size in the early universe ( first 200 or 300 million years) are really rough. Simulations suggest that many of these primordial stars were extremely massive, due to the lack of heavy elements to radiate heat as they collapsed due to gravity. This would suggest that even a little increase in the numbers and sizes of these stars would vastly increase the production of heavy elements vs what the accepted amounts are.

Lithium 7 production in the first few instants after the big bang is an entirely different kettle of fish. Calculations of elemental densities agree with what we observe for many other elemental isotopes. It is really hard to understand why these same calculations fail so miserably for Lithium 7. I suspect that it is being destroyed in some way.
GSwift7
4 / 5 (8) Jul 20, 2012
Satene:

What do you mean by "symmetric"?

As your linked references point out, we have found that galaxies and stars must have formed much more quickly than we thought after the big bang. The presence of heavy elements in mature galaxies isn't any surprise though. The earliest stars should have been large and hot, which means they had short life spans. Very large stars have life spans of only a few million years (a million is only one thousandth of a billion). The question isn't "why are there heavy elements", the question is "how early did stars form".

Here's something neat: Did you know that red dwarfs burn thier fuel so slowly that if one had formed the same day as the big bang, it would still be burning today. The lifespan of a red dwarf is longer than 13 billion years.
Bewia
2.3 / 5 (3) Jul 20, 2012
..simulations suggest that many of these primordial stars were extremely massive, due to the lack of heavy elements to radiate heat as they collapsed due to gravity..
Well, I did see many of these simulations. They all evolved the visible matter from very sparse/diluted state instead. In these models the contemporary galaxies are the most dense state of matter instead. If we consider, how the gravitational collapse and the hydrogen burning is slowed down, whenever the concentration of interstellar gas goes down, I don't consider these models feasible physically. For example, the dark zones between galactic arms are just slightly more sparse, than the rest of galaxy and the glowing of stars effectively stops there. Now we may imagine, how immensely diluted the matter after inflation of Universe was! In addition, Big Bang theory considers, this matter was very hot. The pressure of radiation didn't help its condensation at all.
GSwift7
3.7 / 5 (6) Jul 20, 2012
Parsec:

Estimates of star formation and their size in the early universe ( first 200 or 300 million years) are really rough. Simulations suggest that many of these primordial stars were extremely massive


lol, you were thinking along the same lines I was, in regard to Satene's comment. You're exactly right. If stars started forming at about 300 million years, then the early galaxies Satene is talking about, at about 8 billion years, would have had "7700 million" years of star evolution behind them to form heavy elements. With a life span of just a few million years (lets use 5 million for example), that's enough time for over 1500 consecutive generations of massive stars.
tgoldman
3.7 / 5 (6) Jul 20, 2012
Answer obvious! It's all been gathered up for use in di-Lithium crystals!
Torbjorn_Larsson_OM
3.7 / 5 (3) Jul 20, 2012
@ Bewia:

"The pressure of radiation didn't help its condensation at all."

You are conflating mechanisms. The simulations show how matter (dark and standard) aggregates around primordial fluctuations of the inflation field that inflation has blown up to cosmological scale.

Radiation pressure is what drove universe expansion after matter pressure did, as it started out really dense and not too structured (see the sims). When the radiation pressure decreases due to expansion, the expansion freewheels until dark energy takes over.

Radiation cooling of the first stars in the thusly radiation expanded and freewheeling universe (with radiation diluting) is now possible. Hydrogen molecules and helium atoms has less energy levels than larger atoms and molecules, hence such gas have harder to cool, hence a star that is devoid of metals will be larger.
Shelgeyr
2.1 / 5 (7) Jul 20, 2012
Perhaps the Standard Model is wrong.
ckid
1 / 5 (2) Jul 21, 2012
Does anyone else see the logical error of this article?

a) There is a shortage of lithium-7 in the universe by theory.

b) The temperature of matter swirling into a black hole should create even more lithium-7.

c) Therefore the shortage of lithium-7 is worse than previously thought.

But wait a minute! Any new lithium-7 created near a black hole will never end up being part of the universe at large. It will either cross the event horizon, or at best a very tiny fraction will be radiated as high energy photons.

I think these PHD researchers should be required to take a freshman course in logic.
Doug_Huffman
1 / 5 (1) Jul 22, 2012
Or CKID should publish his defense of solipsism.
Bewia
1.8 / 5 (4) Jul 22, 2012
Any new lithium-7 created near a black hole will never end up being part of the universe at large. It will either cross the event horizon, or at best a very tiny fraction will be radiated as high energy photons.
..or it could be expelled with pressure of accretion radiation into cosmic space...
Torbjorn_Larsson_OM
1 / 5 (1) Jul 23, 2012
@ ckid:

You make three mistakes.

- The shortage of lithium-7 is what is observed. The added excess expected from another source would make the problem of shortage worse.

- The addition through nucleosynthesis in the accretion disks of black holes doesn't get engulfed. Obviously they modeled what would make it out, and conservatively so.

- Atom nuclei doesn't transmute to photons. (Unless they meet their specific anti-nuclei).
MaxwellsDemon
not rated yet Jul 24, 2012
The hyperphysics page on this appears to be wrong: "The modeling of the production of helium and the hydrogen-helium ratio also makes predictions about other nuclear species, particularly 7Li, 2H(deuterium) and 3He. These observed abundances simultaneously fit the big bang model within a narrow range."
http://hyperphysi...hel.html
Given that lithium has lower binding energy than most nuclear species, I wonder if there are regions of higher dark energy where these nuclei are prone to decay into helium and hydrogen, presuming that a positive dark energy field would partly cancel the negative binding energy field of nuclear particles. Given that the decay products would mostly be 1He and 3 x 1H, the critical 3:1 H/He ratio proving big bang nucleosynthesis wouldn't be observably affected. This would require a heterogeneous dark energy model, but we don't know much about what's going on within cosmic bubbles yet.