A large survey, made with ESO's VLT, has shed light on our Galaxy's ancestry. After determining the chemical composition of over 2000 stars in the four nearest dwarf galaxies to our own, astronomers have demonstrated fundamental differences in their make-up, casting doubt on the theory that these diminutive galaxies could ever have formed the building blocks of our Milky Way Galaxy.
"The chemistry we see in the stars in these dwarf galaxies is just not consistent with current cosmological models," said Amina Helmi of the Kapteyn Astronomical Institute in Groningen, The Netherlands, and lead author of the paper presenting the results. "It shows that there is plenty of astronomy to learn in our backyard."
Our Milky Way Galaxy is surrounded by a number of dwarf satellite galaxies, which because of their loosely rounded shape are referred to as 'dwarf spheroidal' galaxies. Faint and diffuse, these dwarf galaxies are a thousand times fainter than the Milky Way itself, making them the least luminous galaxies known.
Modern cosmological models predict that small galaxies form first, and later assemble into larger systems like our Galaxy. Since the Universe initially only contained hydrogen and helium (most of all other chemical elements being synthesized inside stars), dwarf galaxies should have the lowest heavy element content. Not so, say the astronomers.
As part of a large observational programme, the Dwarf galaxies Abundances and Radial-velocities Team (DART), Helmi and her colleagues from institutes in 9 different countries used the FLAMES instrument on ESO's Very Large Telescope to measure the amount of iron in over 2000 individual giant stars in the Fornax, Sculptor, Sextans and Carina dwarf spheroidals.
Their data unearthed fundamental differences in the dwarf galaxy stars' chemical composition compared with those in our galactic halo, calling into question the merger theory as the origin of large galaxies' haloes. Whilst the average abundances of elements in the dwarf spheroidals is comparable with that seen in the Galactic halo, the former are lacking the very metal-poor stars that are seen in the Milky Way - the two types of systems, contrary to theoretical predictions, are essentially of different descent.
"Our results rule out any merging of the nearby dwarf galaxies as a mechanism for building up the Galactic halo, even in the early history of the Universe," said Helmi. "More detailed chemical abundance studies of these systems are needed, as this will tell us more about what happened at those early epochs in our local Universe".
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Researchers create artificial materials atom-by-atom
28.03.2017 | Aalto University
The Institute of Semiconductor Technology and the Institute of Physical and Theoretical Chemistry, both members of the Laboratory for Emerging Nanometrology (LENA), at Technische Universität Braunschweig are partners in a new European research project entitled ChipScope, which aims to develop a completely new and extremely small optical microscope capable of observing the interior of living cells in real time. A consortium of 7 partners from 5 countries will tackle this issue with very ambitious objectives during a four-year research program.
To demonstrate the usefulness of this new scientific tool, at the end of the project the developed chip-sized microscope will be used to observe in real-time...
Astronomers from Bonn and Tautenburg in Thuringia (Germany) used the 100-m radio telescope at Effelsberg to observe several galaxy clusters. At the edges of these large accumulations of dark matter, stellar systems (galaxies), hot gas, and charged particles, they found magnetic fields that are exceptionally ordered over distances of many million light years. This makes them the most extended magnetic fields in the universe known so far.
The results will be published on March 22 in the journal „Astronomy & Astrophysics“.
Galaxy clusters are the largest gravitationally bound structures in the universe. With a typical extent of about 10 million light years, i.e. 100 times the...
Researchers at the Goethe University Frankfurt, together with partners from the University of Tübingen in Germany and Queen Mary University as well as Francis Crick Institute from London (UK) have developed a novel technology to decipher the secret ubiquitin code.
Ubiquitin is a small protein that can be linked to other cellular proteins, thereby controlling and modulating their functions. The attachment occurs in many...
In the eternal search for next generation high-efficiency solar cells and LEDs, scientists at Los Alamos National Laboratory and their partners are creating...
Silicon nanosheets are thin, two-dimensional layers with exceptional optoelectronic properties very similar to those of graphene. Albeit, the nanosheets are less stable. Now researchers at the Technical University of Munich (TUM) have, for the first time ever, produced a composite material combining silicon nanosheets and a polymer that is both UV-resistant and easy to process. This brings the scientists a significant step closer to industrial applications like flexible displays and photosensors.
Silicon nanosheets are thin, two-dimensional layers with exceptional optoelectronic properties very similar to those of graphene. Albeit, the nanosheets are...
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