Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Cut from Different Cloth

08.11.2006
VLT Shows Milky Way's Neighbouring Galaxies Have Different History

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".

| alfa
Further information:
http://www.eso.org

More articles from Physics and Astronomy:

nachricht Black hole spin cranks-up radio volume
15.01.2018 | National Institutes of Natural Sciences

nachricht The universe up close
15.01.2018 | Georg-August-Universität Göttingen

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: Scientists decipher key principle behind reaction of metalloenzymes

So-called pre-distorted states accelerate photochemical reactions too

What enables electrons to be transferred swiftly, for example during photosynthesis? An interdisciplinary team of researchers has worked out the details of how...

Im Focus: The first precise measurement of a single molecule's effective charge

For the first time, scientists have precisely measured the effective electrical charge of a single molecule in solution. This fundamental insight of an SNSF Professor could also pave the way for future medical diagnostics.

Electrical charge is one of the key properties that allows molecules to interact. Life itself depends on this phenomenon: many biological processes involve...

Im Focus: Paradigm shift in Paris: Encouraging an holistic view of laser machining

At the JEC World Composite Show in Paris in March 2018, the Fraunhofer Institute for Laser Technology ILT will be focusing on the latest trends and innovations in laser machining of composites. Among other things, researchers at the booth shared with the Aachen Center for Integrative Lightweight Production (AZL) will demonstrate how lasers can be used for joining, structuring, cutting and drilling composite materials.

No other industry has attracted as much public attention to composite materials as the automotive industry, which along with the aerospace industry is a driver...

Im Focus: Room-temperature multiferroic thin films and their properties

Scientists at Tokyo Institute of Technology (Tokyo Tech) and Tohoku University have developed high-quality GFO epitaxial films and systematically investigated their ferroelectric and ferromagnetic properties. They also demonstrated the room-temperature magnetocapacitance effects of these GFO thin films.

Multiferroic materials show magnetically driven ferroelectricity. They are attracting increasing attention because of their fascinating properties such as...

Im Focus: A thermometer for the oceans

Measurement of noble gases in Antarctic ice cores

The oceans are the largest global heat reservoir. As a result of man-made global warming, the temperature in the global climate system increases; around 90% of...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

10th International Symposium: “Advanced Battery Power – Kraftwerk Batterie” Münster, 10-11 April 2018

08.01.2018 | Event News

See, understand and experience the work of the future

11.12.2017 | Event News

Innovative strategies to tackle parasitic worms

08.12.2017 | Event News

 
Latest News

White graphene makes ceramics multifunctional

16.01.2018 | Materials Sciences

Breaking bad metals with neutrons

16.01.2018 | Materials Sciences

ISFH-CalTeC is “designated test centre” for the confirmation of solar cell world records

16.01.2018 | Power and Electrical Engineering

VideoLinks
B2B-VideoLinks
More VideoLinks >>>