The Spite plateau (or Spite lithium plateau) is a baseline in the abundance of

lithium Lithium (from el, λίθος, lithos, lit=stone) is a chemical element with the symbol Li and atomic number 3. It is a soft, silvery-white alkali metal. Under standard conditions, it is the least dense metal and the least dense solid el ...

found in old stars orbiting the galactic halo. It was named after the astronomers François and Monique Spite, who published the discovery in 1982.

Background

The element lithium was first produced during the

Big Bang The Big Bang event is a physical theory that describes how the universe expanded from an initial state of high density and temperature. Various cosmological models of the Big Bang explain the evolution of the observable universe from the ...

that created the

observable universe The observable universe is a ball-shaped region of the universe comprising all matter that can be observed from Earth or its space-based telescopes and exploratory probes at the present time, because the electromagnetic radiation from these obj ...

. The cosmic abundance of lithium is of interest because it provides several constraints to the various Big Bang models. Those models that fail to satisfy these constraints are therefore subject to rejection or correction by the scientific community. Lithium is readily consumed by fusion with protons at temperatures above , such as is found in the cores of stars. Thus, if the

convection zone A convection zone, convective zone or convective region of a star is a layer which is unstable due to convection. Energy is primarily or partially transported by convection in such a region. In a radiation zone, energy is transported by radiation ...

of a

main sequence In astronomy, the main sequence is a continuous and distinctive band of stars that appears on plots of stellar color versus brightness. These color-magnitude plots are known as Hertzsprung–Russell diagrams after their co-developers, Ejnar Her ...

star cicrulates a star's lithium through the core region (which is believed common in low-mass types K and M), the abundance of lithium in the star should be greatly reduced. Likewise, lithium can be produced in

interstellar matter In astronomy, the interstellar medium is the matter and radiation that exist in the space between the star systems in a galaxy. This matter includes gas in ionic, atomic, and molecular form, as well as dust and cosmic rays. It fills interstellar ...

by spallation collisions with

cosmic ray Cosmic rays are high-energy particles or clusters of particles (primarily represented by protons or atomic nuclei) that move through space at nearly the speed of light. They originate from the Sun, from outside of the Solar System in our own ...

s, or by the evolution of stars of moderate mass.

Lithium estimates

To obtain a good estimate of the primordial abundance of lithium, astronomers François and Monique Spite measured the abundance of lithium in old, population II stars (or old halo stars). Such stars were formed early in the universe out of material that had not been significantly modified by other processes. Their results showed that the curve on a graph of the abundance of lithium versus effective surface temperature formed a plateau among old halo stars for effective temperatures below about: : or roughly 5,600 K. This suggested that the plateau represented the primordial abundance level of lithium in the

Milky Way The Milky Way is the galaxy that includes our Solar System, with the name describing the galaxy's appearance from Earth: a hazy band of light seen in the night sky formed from stars that cannot be individually distinguished by the naked eye ...

, and thus they were able to estimate that the abundance of lithium at the beginning of the galaxy was: : where is the number density of lithium atoms and / or ions, and :: is the number density of hydrogen atoms and / or ions. The current estimates for the primordial abundance of lithium, as measured by this technique, are in tension with the predictions of the standard model of

Big Bang nucleosynthesis In physical cosmology, Big Bang nucleosynthesis (abbreviated BBN, also known as primordial nucleosynthesis) is the production of nuclei other than those of the lightest isotope of hydrogen (hydrogen-1, 1H, having a single proton as a nucleus) du ...

, a discrepancy known as the lithium problem.

References

{{reflist, 25em, refs= {{cite conference , author1=Coc, Alain , author2=Vangioni, Elisabeth , date=May 23–27, 2005 , title=Lithium and Big-Bang Nucleosynthesis , book-title=From Lithium to Uranium: Elemental Tracers of Early Cosmic Evolution , series=

IAU The International Astronomical Union (IAU; french: link=yes, Union astronomique internationale, UAI) is a nongovernmental organisation with the objective of advancing astronomy in all aspects, including promoting astronomical research, outreach ...

Symposium Proceedings , volume=228 , pages=13–22 , location=Paris, France , editor1=Hill, V. , editor2=François, P. , editor3=Primas , publisher=

International Astronomical Union The International Astronomical Union (IAU; french: link=yes, Union astronomique internationale, UAI) is a nongovernmental organisation with the objective of advancing astronomy in all aspects, including promoting astronomical research, outreac ...

Cambridge University Press Cambridge University Press is the university press of the University of Cambridge. Granted letters patent by Henry VIII of England, King Henry VIII in 1534, it is the oldest university press A university press is an academic publishing hou ...

, doi=10.1017/S1743921305005156 , doi-access=free , bibcode=2005IAUS..228...13C {{cite journal , author1=Spite, F. , author2=Spite, M. , date=November 1982 , title=Abundance of lithium in unevolved halo stars and old disk stars - Interpretation and consequences , journal=Astronomy and Astrophysics , volume=115 , issue=2 , pages=357–366 , bibcode=1982A&A...115..357S {{cite journal , last=Fields , first=Brian D. , year=2012 , title=The Primordial Lithium Problem , journal=

Annual Review of Nuclear and Particle Science Annual may refer to: *Annual publication, periodical publications appearing regularly once per year **Yearbook **Literary annual *Annual plant *Annual report *Annual giving *Annual, Morocco, a settlement in northeastern Morocco *Annuals (band), a ...

, volume=61 , issue=1 , pages=47–68 , bibcode = 2011ARNPS..61...47F , arxiv=1203.3551 , doi=10.1146/annurev-nucl-102010-130445 , doi-access=free Big Bang Stellar evolution