"Surprisingly, it is very hard to pin down the age of a star", the lead author of the paper reporting the results, Anna Frebel, explains. "This requires measuring very precisely the abundance of the radioactive elements thorium or uranium, a feat only the largest telescopes such as ESO's VLT can achieve."
This technique is analogous to the carbon-14 dating method that has been so successful in archaeology over time spans of up to a few tens of thousands of years. In astronomy, however, this technique must obviously be applied to vastly longer timescales.
For the method to work well, the right choice of radioactive isotope is critical. Unlike other, stable elements that formed at the same time, the abundance of a radioactive (unstable) isotope decreases all the time. The faster the decay, the less there will be left of the radioactive isotope after a certain time, so the greater will be the abundance difference when compared to a stable isotope, and the more accurate is the resulting age.
Yet, for the clock to remain useful, the radioactive element must not decay too fast - there must still be enough left of it to allow an accurate measurement, even after several billion years.
"Actual age measurements are restricted to the very rare objects that display huge amounts of the radioactive elements thorium or uranium," says Norbert Christlieb, co-author of the report.
Large amounts of these elements have been found in the star HE 1523-0901, an old, relatively bright star that was discovered within the Hamburg/ESO survey . The star was then observed with UVES on the Very Large Telescope (VLT) for a total of 7.5 hours.
A high quality spectrum was obtained that could never have been achieved without the combination of the large collecting power Kueyen, one of the individual 8.2-m Unit Telescopes of the VLT, and the extremely good sensitivity of UVES in the ultraviolet spectral region, where the lines from the elements are observed.
For the first time, the age dating involved both radioactive elements in combination with the three other neutron-capture elements europium, osmium, and iridium.
"Until now, it has not been possible to measure more than a single cosmic clock for a star. Now, however, we have managed to make six measurements in this one star"," says Frebel.
Ever since the star was born, these "clocks" have ticked away over the eons, unaffected by the turbulent history of the Milky Way. They now read 13.2 billion years.
The Universe being 13.7 billion years old, this star clearly formed very early in the life of our own Galaxy, which must also formed very soon after the Big Bang.
Henri Boffin | alfa
Graphene and quantum dots put in motion a CMOS-integrated camera that can see the invisible
30.05.2017 | ICFO-The Institute of Photonic Sciences
New Method of Characterizing Graphene
30.05.2017 | Universität Basel
Scientists have developed a new method of characterizing graphene’s properties without applying disruptive electrical contacts, allowing them to investigate both the resistance and quantum capacitance of graphene and other two-dimensional materials. Researchers from the Swiss Nanoscience Institute and the University of Basel’s Department of Physics reported their findings in the journal Physical Review Applied.
Graphene consists of a single layer of carbon atoms. It is transparent, harder than diamond and stronger than steel, yet flexible, and a significantly better...
The world's highest gain high power laser amplifier - by many orders of magnitude - has been developed in research led at the University of Strathclyde.
The researchers demonstrated the feasibility of using plasma to amplify short laser pulses of picojoule-level energy up to 100 millijoules, which is a 'gain'...
Staphylococcus aureus is a feared pathogen (MRSA, multi-resistant S. aureus) due to frequent resistances against many antibiotics, especially in hospital infections. Researchers at the Paul-Ehrlich-Institut have identified immunological processes that prevent a successful immune response directed against the pathogenic agent. The delivery of bacterial proteins with RNA adjuvant or messenger RNA (mRNA) into immune cells allows the re-direction of the immune response towards an active defense against S. aureus. This could be of significant importance for the development of an effective vaccine. PLOS Pathogens has published these research results online on 25 May 2017.
Staphylococcus aureus (S. aureus) is a bacterium that colonizes by far more than half of the skin and the mucosa of adults, usually without causing infections....
Physicists from the University of Würzburg are capable of generating identical looking single light particles at the push of a button. Two new studies now demonstrate the potential this method holds.
The quantum computer has fuelled the imagination of scientists for decades: It is based on fundamentally different phenomena than a conventional computer....
An international team of physicists has monitored the scattering behaviour of electrons in a non-conducting material in real-time. Their insights could be beneficial for radiotherapy.
We can refer to electrons in non-conducting materials as ‘sluggish’. Typically, they remain fixed in a location, deep inside an atomic composite. It is hence...
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30.05.2017 | Life Sciences
30.05.2017 | Life Sciences
30.05.2017 | Physics and Astronomy