Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

An Impossible Star

01.09.2011
Astronomers observe a 13-billion-year-old star with an unusual chemical composition

A team of European astronomers led by a scientist of Heidelberg University has discovered a star that according to standard astronomical thinking should not be able to exist: it is made up almost entirely of hydrogen and helium with only minute traces of other elements.


An impossible star: A team of European astronomers has investigated the faint and extremely metal-poor star SDSS J102915+172927. It dates back to the early days of the Universe and is probably over 13 billion years old. Source: ESO/Digitized Sky Survey 2

In terms of the generally accepted theory of star formation, this unusual chemical composition puts the star dating from the early stages of the Universe into a “forbidden zone”. “For all we know, it should never have come into being in the first place,” says Dr. Elisabetta Caffau of Heidelberg University’s Centre for Astronomy (ZAH). The findings of the investigation, which was carried out with the Very Large Telescope of the European Southern Observatory (ESO), will be published in “Nature” on 1 September 2011.

The extremely faint star in the Leo constellation goes by the cumbersome designation “SDSS J102915+172927”. It was catalogued in the course of the Sloan Digital Sky Survey (SDSS), an international project scanning certain sectors of the sky with spectral lines. The figures in the designation refer to its position in the sky. The star has slightly less mass than the Sun and is probably over 13 billion years old. According to the observations of the European research team, SDSS J102915+172927 has the lowest proportion of chemical elements heavier than helium of any star investigated so far.

The properties of the star were investigated with the two spectrographs X-Shooter and UVES of the ESO’s Very Large Telescope (VLT) in Chile. With these devices, the light of celestial bodies can be split into its colour components. Spectrum analysis, developed by Gustav Kirchhoff and Robert Bunsen in the mid-19th century in Heidelberg, is used to determine the relative proportion of chemical elements in a star’s atmosphere. This is how the astronomers established that the metal content of SDSS J102915+172927 is 20,000 times lower than that of the Sun. In their first measurements the astronomers spotted just one chemical element heavier than helium: calcium. It was only through additional observation that the scientists from France, Germany and Italy were able to identify other metals.

“The generally accepted theory states that because of their low mass and the extremely small proportion of heavy elements, stars like this one should not be able to exist at all,” says Dr. Caffau, who conducts research at the Königstuhl State Observatory of Heidelberg University’s Centre for Astronomy. “Received thinking suggests that in this case the gas and dust clouds giving rise to such a star could not have condensed sufficiently for the purpose. This is the first time a star has been discovered in the ‘forbidden zone’ of star formation and it was a big surprise for us. Now astrophysicists will have to rethink some of their models for the formation of stars.” Dr. Caffau is the lead author of the study published in “Nature”.

Cosmologists believe that, along with traces of lithium, the lightest elements hydrogen and helium came into existence shortly after the Big Bang. Almost all heavier elements were formed a great deal later, either through fusion processes in the interior of stars or in the course of supernova explosions at the end of a star’s life. After the explosion the metal-rich material mixes with the interstellar medium, i.e. the matter in the space between the stars. The next generation of stars is formed from this metal-enriched material. The metal content of the newly formed stars is higher than in the previous generation. “This means that the proportion of metals also tells us how old a star is, or rather how many generations of stars the material it consists of has been through,” says Dr. Caffau. “The fact that SDSS J102915+172927 is extremely metal-poor means that this star must stem from the early days of the Universe. In fact, it may be one of the oldest stars ever found.”

Another surprise is the paucity of lithium in SDSS J102915+172927, as according to Dr. Caffau, a star of this age should have more or less the same chemical composition as the Universe just after the Big Bang. But the star’s lithium content is fifty times smaller than cosmological calculations on element formation would lead us to expect. For the European astronomer team, it is a mystery how the lithium that must have formed at the beginning of the Universe was destroyed in this particular star. But the scientists are convinced that this strange star is not alone. “We have a whole series of candidates whose metal content may be just as low as that of SDSS J102915+172927, if not lower,” says Dr. Caffau. “We are planning to observe them with the VLT to see if this is the case.” For the astronomers, it is the next step towards exploring the very first generation of stars.

For more information, go to http://www.lsw.uni-heidelberg.de/projects/galactic_archaeology.

Original publication:
E. Caffau, P. Bonifacio, P. François, L. Sbordone, L. Monaco, M. Spite, F. Spite, H.-G. Ludwig, R. Cayrel, S. Zaggia, F. Hammer, S. Randich, P. Molaro, V. Hill: An extremely primitive halo star in the Galactic halo, Nature (1 September 2011)

Contact:

Dr. Guido Thimm
Zentrum für Astonomie der Universität Heidelberg (ZAH)
phone: +49 6221 541805
thimm@ari.uni-heidelberg.de
Dr. Elisabetta Caffau
Zentrum für Astronomie der Universität Heidelberg (ZAH)
phone: +49 6221 541787
e.caffau@lsw.uni-heidelberg.de
Communications and Marketing
Press Office, phone +49 6221 542311
presse@rektorat.uni-heidelberg.de

Marietta Fuhrmann-Koch | idw
Further information:
http://www.uni-heidelberg.de

More articles from Physics and Astronomy:

nachricht Significantly more productivity in USP lasers
06.12.2016 | Fraunhofer-Institut für Lasertechnik ILT

nachricht Shape matters when light meets atom
05.12.2016 | Centre for Quantum Technologies at the National University of Singapore

All articles from Physics and Astronomy >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Shape matters when light meets atom

Mapping the interaction of a single atom with a single photon may inform design of quantum devices

Have you ever wondered how you see the world? Vision is about photons of light, which are packets of energy, interacting with the atoms or molecules in what...

Im Focus: Novel silicon etching technique crafts 3-D gradient refractive index micro-optics

A multi-institutional research collaboration has created a novel approach for fabricating three-dimensional micro-optics through the shape-defined formation of porous silicon (PSi), with broad impacts in integrated optoelectronics, imaging, and photovoltaics.

Working with colleagues at Stanford and The Dow Chemical Company, researchers at the University of Illinois at Urbana-Champaign fabricated 3-D birefringent...

Im Focus: Quantum Particles Form Droplets

In experiments with magnetic atoms conducted at extremely low temperatures, scientists have demonstrated a unique phase of matter: The atoms form a new type of quantum liquid or quantum droplet state. These so called quantum droplets may preserve their form in absence of external confinement because of quantum effects. The joint team of experimental physicists from Innsbruck and theoretical physicists from Hannover report on their findings in the journal Physical Review X.

“Our Quantum droplets are in the gas phase but they still drop like a rock,” explains experimental physicist Francesca Ferlaino when talking about the...

Im Focus: MADMAX: Max Planck Institute for Physics takes up axion research

The Max Planck Institute for Physics (MPP) is opening up a new research field. A workshop from November 21 - 22, 2016 will mark the start of activities for an innovative axion experiment. Axions are still only purely hypothetical particles. Their detection could solve two fundamental problems in particle physics: What dark matter consists of and why it has not yet been possible to directly observe a CP violation for the strong interaction.

The “MADMAX” project is the MPP’s commitment to axion research. Axions are so far only a theoretical prediction and are difficult to detect: on the one hand,...

Im Focus: Molecules change shape when wet

Broadband rotational spectroscopy unravels structural reshaping of isolated molecules in the gas phase to accommodate water

In two recent publications in the Journal of Chemical Physics and in the Journal of Physical Chemistry Letters, researchers around Melanie Schnell from the Max...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

ICTM Conference 2017: Production technology for turbomachine manufacturing of the future

16.11.2016 | Event News

Innovation Day Laser Technology – Laser Additive Manufacturing

01.11.2016 | Event News

#IC2S2: When Social Science meets Computer Science - GESIS will host the IC2S2 conference 2017

14.10.2016 | Event News

 
Latest News

Speed data for the brain’s navigation system

06.12.2016 | Health and Medicine

What happens in the cell nucleus after fertilization

06.12.2016 | Life Sciences

IHP presents the fastest silicon-based transistor in the world

05.12.2016 | Power and Electrical Engineering

VideoLinks
B2B-VideoLinks
More VideoLinks >>>