From IAC via Manu: “IAC astronomers find one of the first stars formed in the Milky Way”


Manu Garcia, a friend from IAC.

The universe around us.
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Dec. 19, 2017
Contact IAC:
David Sánchez Aguado
aguado@iac.es

Jonay I. González Hernández
jonay@iac.es

Researchers at the Instituto de Astrofísica de Canarias (IAC) have identified, using the Gran Telescopio de Canarias (GTC) a star which is a key to the formation of the first chemical elements in the Galaxy. The results of this research are published today in the scientific journal The Astrophysical Journal Letters.

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The study presents the discovery of one of the stars with the least content of “metals” (heavy elements). Known. Th estar is at 7,500 light years from Earth, in the halo of the Milky Way, and is along the line of sight to the constellation of the Lynx. The star is still on the Main Sequence, the stage at which most stars spend the major part of their lives. The source of energy of these stars is, as always, the fusión of hydrogen in their cores, and their surface temperaturas and luminosities are almost constant with time. Another of its properties is its low mass, around 0.7 times the mass of the Sun, although it has a surface temperatura 400 degrees hotter.

This discovery was made using spectra obtained with OSIRIS (Optical System for Imaging and low-intermediate-Resolution Integrated Spectoscopy) on the Gran Telescopio Canarias (GTC), at the Roque de los Muchachos Observatory (Garafía, La Palma).

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OSIRIS on GTC

Spectroscopy allows us to decompose the light of celestial objects to study their physical and chemical properties, and thanks to this we know that J0815+4729 has only a millionth part of the calcium and iron that the Sun contains, but it has a comparatively huge content of carbón, almost 15% of the solar abundance.

“ We know of only a few stars (which can be counted on the fingers of a hand) of this type in the halo, where the oldest and most metal-poor stars in our Galaxy are found”, explains David Aguado, an FPI-SO (Severo Ochoa-Training of Research Personnel) research student at the IAC and the University of La Laguna (ULL) who si the first author of the article.

“Theory predicts that these stars could form just after, and using material fom, the first supernovae, whose progenitors were the first massive stars in the Galaxy, around 300 million years after the Big Bang” says Jonay González Hernández, a Ramon y Cajal researcher at the IAC and one of the authors of the article. “In spite of its age, and of its distance away from us, we can still observe it” he adds.

In fact this star was first identified from the SDASS (Sloan Digital Sky Survey) data base within the BOSS (Baryon Oscillation Spectroscopic Survey) project, and it was later observed with the ISIS intermediate dispersion spectrograph on the William Herschel Telescope (WHT) of the Isaac Newton Group of Telescopes which is also at the Roque de los Muchachos Observatory.

SDSS Telescope at Apache Point Observatory, NM, USA, Altitude 2,788 meters (9,147 ft)

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ISIS intermediate dispersion spectrograph on the William Herschel Telescope (WHT) of the Isaac Newton Group of Telescopes

Isaac Newton Group telescopes, at Roque de los Muchachos Observatory on La Palma in the Canary Islands, Spain, at an altitude of 2400m


ING 4 meter William Herschel Telescope at Roque de los Muchachos Observatory on La Palma in the Canary Islands, 2,396 m (7,861 ft)

“This star was tucked away in the data base of the BOSS project, among a million stellar spectra which we have analysed to identify it, which required a considerable observational and computational effort” stated Carlos Allende Prieto, another IAC researcher, and a coauthor of this article. “It needs high resolution spectroscopy on large telescopes to try to detect the verious chemical elements in the star which can help us to understand the first supernovae and their progenitors” he emphasized.

In the near future the HORS high resolution spectrograph, at presently in a trial phse on the GTC, will be a key instrument for the chemical analysis of weak stars such as J0815+4729

Rafael Rebolo, the director of the IAC and a coauthor of the paper, explains that “Detecting lithium gives us crucial information related to Big Bang nucleosynthesis. We are working on a spectrograph of high resolution and wide spectral range inorder to be able to measure (among other things) the detailed chemical composition of stars with unique properties such as J0815+4719”

The Observatories of the Instituto de Astrofísica de Canarias (IAC) and the Gran Telescopio CANARIAS ( GTC) are part of the network of Singular Scientific and Technical Insfrastructure (ICTS) of Spain.

IAC

Instituto de Astrofísica de Canarias – IAC

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The Instituto de Astrofísica de Canarias(IAC) is an international research centre in Spain which comprises:

The Instituto de Astrofísica, the headquarters, which is in La Laguna (Tenerife).
The Centro de Astrofísica en La Palma (CALP)
The Observatorio del Teide (OT), in Izaña (Tenerife).
The Observatorio del Roque de los Muchachos (ORM), in Garafía (La Palma).

These centres, with all the facilities they bring together, make up the European Northern Observatory(ENO).

The IAC is constituted administratively as a Public Consortium, created by statute in 1982, with involvement from the Spanish Government, the Government of the Canary Islands, the University of La Laguna and Spain’s Science Research Council (CSIC).

The International Scientific Committee (CCI) manages participation in the observatories by institutions from other countries. A Time Allocation Committee (CAT) allocates the observing time reserved for Spain at the telescopes in the IAC’s observatories.

The exceptional quality of the sky over the Canaries for astronomical observations is protected by law. The IAC’s Sky Quality Protection Office (OTPC) regulates the application of the law and its Sky Quality Group continuously monitors the parameters that define observing quality at the IAC Observatories.

The IAC’s research programme includes astrophysical research and technological development projects.

The IAC is also involved in researcher training, university teaching and outreachactivities.

The IAC has devoted much energy to developing technology for the design and construction of a large 10.4 metre diameter telescope, the ( Gran Telescopio CANARIAS, GTC), which is sited at the Observatorio del Roque de los Muchachos.


Gran Telescopio Canarias at the Roque de los Muchachos Observatory on the island of La Palma, in the Canaries, SpainGran Telescopio CANARIAS, GTC