Tuesday, July 5, 2022

Scientists discovered lithium in the oldest and coldest brown dwarf

Ancient brown dwarf with lithium deposits intact.

Using the OSIRIS spectrograph on the Gran Telescopio Canarias (GTC), a team of scientists at the Instituto de Astrofísica de Canarias (IAC) and the Instituto Nacional de Astrofísica, Óptica y Electrónica (INAOE), Mexico- has discovered lithium in the oldest and coldest brown dwarf, Reid 1B. They also discovered that the origin of this cosmic lithium dates back before the formation of the system to which Reid 1B belongs.

Astronomers have detected and followed the orbital motions of binaries formed by brown dwarfs in the solar neighborhood in the past two decades. They have determined their masses dynamically using Kepler’s laws. The primary component has enough mass to burn lithium in some of these systems, whereas the second component may not have this mass. However, until now, the theoretical models have not been put to the test.

Using the OSIRIS spectrograph on the Gran Telescopio Canarias (GTC, or Grantecan), a team of scientists at the Instituto de Astrofísica de Canarias (IAC) and the Instituto Nacional de Astrofísica, Óptica y Electrónica (INAOE) made high sensitivity spectroscopic observations of two binaries whose components are brown dwarfs. They made the observations between February and August this year.

The substellar object Reid 1B is almost 1.100 million years. It has a dynamical mass 41 times bigger than that of Jupiter (the largest planet in the Solar System), is 16.9 light-years away from us.

Scientists noted, “The lithium is preserved up to a dynamical mass which is 10% lower than predicted by the most recent theoretical models. This discrepancy seems to be significant and suggests that there is something in the behavior of brown dwarfs that we still don’t understand.”

Eduardo Lorenzo Martín Guerrero de Escalante, Research Professor of the Higher Council for Scientific Research (CSIC) at the IAC, said, “We have been following the trail of lithium in brown dwarfs for three decades, and finally we have been able to make a precise determination of the boundary in mass between its preservation and its destruction, and compare this with the theoretical predictions.” 

“There are thousands of millions of brown dwarfs in the Milky Way. The lithium contained in brown dwarfs is the largest known deposit of this valuable element in our cosmic neighborhood.”

Carlos del Burgo Díaz, a co-author of the article, a researcher at the INAOE, a public research center of the Mexican CONACYT, explains that “although primordial lithium was created 13.800 million years ago, together with hydrogen and helium, as a result of the nuclear reactions in the primordial fireball of the Big Bang, now there is as much as four times more lithium in the Universe.”

According to these scientists, “Although this element can be destroyed, it is also created in explosive events such as novae and supernovae, so that brown dwarfs such as Reid 1B can wrap it up and protect it as if it was a chest of hidden treasure.”

Journal Reference:

  1. Martín, Eduardo L.; Lodieu, Nicolas et al. New constraints on the minimum mass for thermonuclear lithium burning in brown dwarfs. DOI: 10.1093/mnras/stab2969
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