From IAC Institute of Astrophysics of the Canary Islands [Instituto de Astrofísica de Canarias] (ES) : “Astronomers discover ancient brown dwarf with lithium deposits intact”
From IAC Institute of Astrophysics of the Canary Islands [Instituto de Astrofísica de Canarias] (ES)
24/11/2021
Contacts:
Dr. Eduardo Martín Guerrero,
Dr. Carlos del Burgo
The Spanish-Mexican team has found that the boundary between those objects which destroy lithium and those which preserve it lies at 51.5 times the mass of Jupiter. The brown dwarf Reid 1B is a major deposti of lithium which will never be destroyed. Planets such as Jupiter and the Earth are even less massive and do not destroy their lithium. The Sun has destroyed all the lithium that was in its nucleus and preserves some in its upper layers, which are slowly mixing with its interior. Credit: Gabriel Pérez Díaz, SMM (IAC).
A team of researchers at The National Institute for Astrophysics, Optics and Electronics(MX), has discovered lithium in the oldest and coldest brown dwarf where the presence of this valuable element has been confirmed so far. This substellar object, called Reid 1B, preserves intact the earliest known lithium deposit in our cosmic neighbourhood, dating back to a time before the formation of the binary system to which it belongs. The discovery was made using the OSIRIS spectrograph on the Gran Telescopio Canarias (GTC) [below], at The Roque de los Muchachos Observatory | Instituto de Astrofísica de Canarias • IAC(ES),[below] in the Canary Islands.
IAC Gran Telescopio Canarias OSIRIS spectrograph.
The study has just been published in the journal MNRAS.
Comparación entre las masas dinámicas y termonucleares en sistemas binarios de enanas marrones. Más información: http://www.iac.es.
Brown dwarfs, also known as “coffee coloured dwarfs” or “failed stars” are the natural link between stars and planets. They are more massive than Jupiter but now sufficiently to burn hydrogen, which is the fuel the stars use to shine. For that reason these substellar objects were not observed until observers detected them in the mid 1990’s. They are particularly interesting because it was predicted that some of them could preserve intact their content of lithium, sometimes known as “white petroleum” because of its rarity and its relevance.
In the past twenty years astronomers have detected, and followed the orbital motions of binaries formed by brown dwarfs in the solar neighbourhood. They have determined their masses dynamically using Kepler’s laws, the mathematical formulae produced in the XVII century by Johannes Kepler to describe the motions of astronomical bodies moving under the effects of their mutual gravitation, such as the system formed by the Earth and the Sun. In some of these systems the primary component has a mass sufficient to burn lithium while the secondary may not have this mass. However until now the theoretical models had not been put to the test.
Using the OSIRIS spectrograph on the Gran Telescopio Canarias (GTC, or Grantecan) currently the largest optical and infrared telescope in the world, at the Roque de los Muchachos Observatory (ORM), a team of researchers at the Instituto de Astrofísica de Canarias (IAC) and the Instituto Nacional de Astrofísica, Óptica y Electrónica (INAOE) made high sensitivity spectroscopic observations, between February and August this year, of two binaries whose components are brown dwarfs.
They did not detect lithium in three of them, but they did find it in Reid 1B, the faintest and coolest of the four. Doing this they made a remarkable discovery, a deposit of cosmic lithium which is not destroyed, whose origin dates back before the formation of the system to which Reid 1B belongs. It is, in fact, the coolest, faintest extrasolar object where lithium has been found, in a quantity 13 thousand times greater than the amount there is on Earth. This object, which has an age of 1.100 million years, and 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.
A chest of hidden treasure
Observations of lithium in brown dwarfs allow us to estimate their masses with a degree of accuracy, based on nuclear reactions. The thermonuclear masses found this way must be consistent with the dynamical masses found, with less uncertainty, from orbital analysis. However the researchers have found that the lithium is preserved up to a dynamical mass which is 10% lower than that predicted by the most recent theoretical models. This discrepancy seems to be significant, and suggests that there is something in the behaviour of brown dwarfs that we still don’t understand.
“We have been following the trail of lithium in brown dwarfs for three decades” says Eduardo Lorenzo Martín Guerrero de Escalante, Research Professor of the Higher Council for Scientific Research (CSIC) at the IAC who is the first author of the article, “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”. The researcher adds that “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 neighbourhood”.
Carlos del Burgo Díaz co-author of the article, a researcher at the INAOE, a public research centre 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 he 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 this researcher “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”.
This research has been financed by funding from the Spanish Ministry of Economic Affairs and Digital Transformation (MINECO) and by the European Fund for Regional Developomente (FEDER) via project PID2019-109522GB-C53.
The Gran Telescopio Canarias, and the Observatories of the Instituto de Astrofísica de Canarias (IAC) are part of the network of Singular Scientific and Technical Infrastructures (ICTS) of Spain.
See the full article here .
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IAC Institute of Astrophysics of the Canary Islands [Instituto de Astrofísica de Canarias] (ES) operates two astronomical observatories in the Canary Islands:
Roque de los Muchachos Observatory on La Palma
Teide Observatory on Tenerife.
The Instituto de Astrofísica the headquarters, which is in La Laguna (Tenerife).
Observatorio del Roque de los Muchachos at La Palma (ES) at an altitude of 2400m.
The seeing statistics at ORM make it the second-best location for optical and infrared astronomy in the Northern Hemisphere, after Mauna Kea Observatory Hawaii (US).
Maunakea Observatories Hawai’i (US) altitude 4,213 m (13,822 ft).
The site also has some of the most extensive astronomical facilities in the Northern Hemisphere; its fleet of telescopes includes the 10.4 m Gran Telescopio Canarias, the world’s largest single-aperture optical telescope as of July 2009, the William Herschel Telescope (second largest in Europe), and the adaptive optics corrected Swedish 1-m Solar Telescope.
Isaac Newton Group 4.2 meter William Herschel Telescope at Roque de los Muchachos Observatory on La Palma in the Canary Islands(ES), 2,396 m (7,861 ft).
The observatory was established in 1985, after 15 years of international work and cooperation of several countries with the Spanish island hosting many telescopes from Britain, The Netherlands, Spain, and other countries. The island provided better seeing conditions for the telescopes that had been moved to Herstmonceux by the Royal Greenwich Observatory, including the 98 inch aperture Isaac Newton Telescope (the largest reflector in Europe at that time). When it was moved to the island it was upgraded to a 100-inch (2.54 meter), and many even larger telescopes from various nations would be hosted there.
Tiede Observatory, Tenerife, Canary Islands (ES)
Teide Observatory [Observatorio del Teide], IAU code 954, is an astronomical observatory on Mount Teide at 2,390 metres (7,840 ft), located on Tenerife, Spain. It has been operated by the Instituto de Astrofísica de Canarias since its inauguration in 1964. It became one of the first major international observatories, attracting telescopes from different countries around the world because of the good astronomical seeing conditions. Later the emphasis for optical telescopes shifted more towards Roque de los Muchachos Observatory on La Palma.
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