Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Milky Way Past Was More Turbulent Than Previously Known

06.04.2004


Results of 1001 observing nights shed new light on our Galaxy



Unknown history

Home is the place we know best. But not so in the Milky Way - the galaxy in which we live. Our knowledge of our nearest stellar neighbours has long been seriously incomplete and - worse - skewed by prejudice concerning their behaviour. Stars were generally selected for observation because they were thought to be "interesting" in some sense, not because they were typical. This has resulted in a biased view of the evolution of our Galaxy.


The Milky Way started out just after the Big Bang as one or more diffuse blobs of gas of almost pure hydrogen and helium. With time, it assembled into the flattened spiral galaxy which we inhabit today. Meanwhile, generation after generation of stars were formed, including our Sun some 4,700 million years ago.

But how did all this really happen? Was it a rapid process? Was it violent or calm? When were all the heavier elements formed? How did the Milky Way change its composition and shape with time? Answers to these and many other questions are "hot" topics for the astronomers who study the birth and evolution of the Milky Way and other galaxies.

Now the rich results of a 15 year-long marathon survey by a Danish-Swiss-Swedish research team are providing some of the
answers.

1,001 nights at the telescopes

The team spent more than 1,000 observing nights over 15 years at the Danish 1.5-m telescope of the European Southern Observatory at La Silla (Chile) and at the Swiss 1-m telescope of the Observatoire de Haute-Provence (France). Additional observations were made at the Harvard-Smithsonian Center for Astrophysics in the USA. A total of more than 14,000 solar-like stars (so-called F- and G-type stars) were observed at an average of four times each - a total of no less than 63,000 individual spectroscopic observations!

This now complete census of neighbourhood stars provides distances, ages, chemical analysis, space velocities and orbits in the general rotation of the Milky Way. It also identifies those stars (about 1/3 of them all) which the astronomers found to be double or multiple. This very complete data set for the stars in the solar neighbourhood will provide food for thought by astronomers for years to come.

A dream come true

These observations provide the long-sought missing pieces of the puzzle to get a clear overview of the solar neighbourhood. They effectively mark the conclusion of a project started more than twenty years ago.

In fact, this work marks the fulfilment of an old dream by Danish astronomer Bengt Stroemgren (1908-1987), who pioneered the study of the history of the Milky Way through systematic studies of its stars.

Already in the 1950’s he designed a special system of colour measurements to determine the chemical composition and ages of many stars very efficiently. And the Danish 50-cm and 1.5-m telescopes at the ESO La Silla Observatory (Chile) were constructed to make such projects possible.

Another Danish astronomer, Erik Heyn Olsen, made the first step in the 1980’s by measuring the flux (light intensity) in several wavebands in the "Stroemgren photometric system") of 30,000 A, F and G stars over the whole sky to a fixed brightness limit. Next, ESA’s Hipparcos satellite determined precise distances and velocities in the plane of the sky for these and many other stars.

The missing link was the motions along the line of sight (the so-called radial velocities). They were then measured by the present team from the Doppler shift of spectral lines of the stars (the same technique that is used to detect planets around other stars), using the specialized CORAVEL instrument.

Stellar orbits in the Milky Way

With the velocity information completed, the astronomers can now compute how the stars have wandered around in the Galaxy in the past, and where they will go in the future.

Birgitta Nordstroem, leader of the team, explains: "For the first time we have a complete set of observed stars that is a fair representation of the stellar population in the Milky Way disc in general. It is large enough for a proper statistical analysis and also has complete velocity and binary star information. We have just started the analysis of this dataset ourselves, but we know that our colleagues worldwide will rush to join in the interpretation of this treasure trove of information."

The team’s initial analysis indicates that objects like molecular clouds, spiral arms, black holes, or maybe a central bar in the Galaxy, have stirred up the motion of the stars throughout the entire history of the Milky Way disc.

This in turn reveals that the evolution of the Milky Way was far more complex and chaotic than traditional, simplified models have long so far assumed. Supernova explosions, galaxy collisions, and infall of huge gas clouds have made the Milky Way a very lively place indeed!

Richard West | ESO
Further information:
http://www.eso.org/outreach/press-rel/pr-2004/pr-08-04.html

More articles from Physics and Astronomy:

nachricht APEX takes a glimpse into the heart of darkness
25.05.2018 | Max-Planck-Institut für Radioastronomie

nachricht First chip-scale broadband optical system that can sense molecules in the mid-IR
24.05.2018 | Columbia University School of Engineering and Applied Science

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: Powerful IT security for the car of the future – research alliance develops new approaches

The more electronics steer, accelerate and brake cars, the more important it is to protect them against cyber-attacks. That is why 15 partners from industry and academia will work together over the next three years on new approaches to IT security in self-driving cars. The joint project goes by the name Security For Connected, Autonomous Cars (SecForCARs) and has funding of €7.2 million from the German Federal Ministry of Education and Research. Infineon is leading the project.

Vehicles already offer diverse communication interfaces and more and more automated functions, such as distance and lane-keeping assist systems. At the same...

Im Focus: Molecular switch will facilitate the development of pioneering electro-optical devices

A research team led by physicists at the Technical University of Munich (TUM) has developed molecular nanoswitches that can be toggled between two structurally different states using an applied voltage. They can serve as the basis for a pioneering class of devices that could replace silicon-based components with organic molecules.

The development of new electronic technologies drives the incessant reduction of functional component sizes. In the context of an international collaborative...

Im Focus: LZH showcases laser material processing of tomorrow at the LASYS 2018

At the LASYS 2018, from June 5th to 7th, the Laser Zentrum Hannover e.V. (LZH) will be showcasing processes for the laser material processing of tomorrow in hall 4 at stand 4E75. With blown bomb shells the LZH will present first results of a research project on civil security.

At this year's LASYS, the LZH will exhibit light-based processes such as cutting, welding, ablation and structuring as well as additive manufacturing for...

Im Focus: Self-illuminating pixels for a new display generation

There are videos on the internet that can make one marvel at technology. For example, a smartphone is casually bent around the arm or a thin-film display is rolled in all directions and with almost every diameter. From the user's point of view, this looks fantastic. From a professional point of view, however, the question arises: Is that already possible?

At Display Week 2018, scientists from the Fraunhofer Institute for Applied Polymer Research IAP will be demonstrating today’s technological possibilities and...

Im Focus: Explanation for puzzling quantum oscillations has been found

So-called quantum many-body scars allow quantum systems to stay out of equilibrium much longer, explaining experiment | Study published in Nature Physics

Recently, researchers from Harvard and MIT succeeded in trapping a record 53 atoms and individually controlling their quantum state, realizing what is called a...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

VideoLinks
Industry & Economy
Event News

In focus: Climate adapted plants

25.05.2018 | Event News

Save the date: Forum European Neuroscience – 07-11 July 2018 in Berlin, Germany

02.05.2018 | Event News

Invitation to the upcoming "Current Topics in Bioinformatics: Big Data in Genomics and Medicine"

13.04.2018 | Event News

 
Latest News

In focus: Climate adapted plants

25.05.2018 | Event News

Flow probes from the 3D printer

25.05.2018 | Machine Engineering

Less is more? Gene switch for healthy aging found

25.05.2018 | Life Sciences

VideoLinks
Science & Research
Overview of more VideoLinks >>>