Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:


How nature shapes the birth of stars

Using state of the art computer simulations, a team of astronomers from the University of Bonn in Germany have found the first evidence that the way in which stars form depends on their birth environment. The team, based at the University of Bonn in Germany, publish their results in the journal Monthly Notices of the Royal Astronomical Society.

Stars are thought to form in interstellar space from dark clouds of gas and dust. Their properties are expected to depend on the conditions of their dusty birth environment, in the same way that the temperature and constitution of clouds on Earth determines whether we experience drizzly weather, rain with large or small droplets, or a hail shower.

A Hubble Space Telescope image of the massive star cluster R 136 in the Large Magellanic Cloud. R136 is a potential birth site of much more massive stars, although unconfirmed, than observed in "normal" sites of present-day star formation. Credit: NASA, J. Trauger (JPL), J. Westphal (Caltech)

In contrast, until now stars have appeared to unexpectedly form in the same manner everywhere. “Sites of star formation are the bad weather regions in a galaxy and the forming stars are, in a very rough analogy, like the raindrops condensing out of this material”, comments team member Prof. Dr. Pavel Kroupa.

The group of scientists now have evidence that the mass distribution of stars does indeed depend on the environment in which they form. “Surprisingly, this evidence does not come to us from young regions of ongoing star formation, but from a very old class of objects, so called globular star clusters”, says Dr. Michael Marks, lead author of the new paper. “The number of observed stars less massive than our Sun in globular clusters is at odds with their structure.”

Globular clusters are massive congregations of thousands stars surrounding our Galaxy, the Milky Way. Star formation in these clusters ceased billions of years ago. “Nevertheless, using our simulations we found that the connection between star formation and birth environment can be understood when invoking a process that occurs very early in the life of any cluster, called residual-gas expulsion“, continues Marks.

Once a star completes its formation it starts to shine and eventually the radiation coming from the cluster of freshly-hatched stars quickly drives out the gas from which they formed. The region of star birth is then destroyed, leaving behind stars of different masses. “This process leads to expansion of the whole aggregate of stars with the accompanying stripping of some of the stars from the cluster by the gravitational attraction of the young Milky Way. The faster the gas is blown out the stronger is the expansion and the more stars are removed”, Kroupa explains. He adds, “The imprint of this process is still visible in the present-day mass distribution”. This means that careful observations of present-day stellar populations in globular clusters allow their initial star content to be reconstructed.

The astronomers find globular clusters must have formed with many more massive stars than are counted in individual star forming regions today. “Otherwise the star birth region a globular cluster formed from is not destroyed quickly enough and the subsequent expansion is too weak to remove enough stars from the cluster”, says Marks. “If this had happened the distribution of masses of stars we see today would be quite different”. The deduced differences in the number of massive stars having formed in globular clusters depending on the cloud conditions is indeed in agreement with theoretical expectation.

According to their results, differences in the initial star content appear only when conditions in the star birth regions are very extreme compared to those we see today. “We do not observe these extreme environments in the present day, but these may have well been frequent when globular clusters were born around 12 billion years ago”, Marks states. Their work predicts that stars form in the same way, with the same range of masses, in different sites in the present day Milky Way.

Kroupa summarises their results. “With this work, we might have uncovered the long expected systematic differences in the star formation process”. The Bonn astronomers now plan to use further simulations to study the effect of these differences on the long-term evolution of globular star clusters.

The new work appears in "Evidence for top-heavy stellar initial mass functions with increasing density and decreasing metallicity", M. Marks, P. Kroupa, J. Dabringhausen and M. Pawlowski, Monthly Notices of the Royal Astronomical Society. A preprint of the paper can be seen at

Prof. Dr. Pavel Kroupa
Argelander-Institut für Astronomie der Universität Bonn
Tel. +49 (0)228 736140
Mob: +49 (0)177 9566127
Dr Michael Marks
Argelander-Institut für Astronomie der Universität Bonn
Max-Planck-Institut für Radioastronomie in Bonn
Tel. +49 (0)228 733653
Media contact
Dr Robert Massey
Royal Astronomical Society
Tel: +44 (0)20 7734 3307 x214
Mob: +44 (0)794 124 8035
Further information
A preprint of the new work appears in
The Royal Astronomical Society (RAS,, founded in 1820, encourages and promotes the study of astronomy, solar-system science, geophysics and closely related branches of science. The RAS organizes scientific meetings, publishes international research and review journals, recognizes outstanding achievements by the award of medals and prizes, maintains an extensive library, supports education through grants and outreach activities and represents UK astronomy nationally and internationally. Its more than 3500 members (Fellows), a third based overseas, include scientific researchers in universities, observatories and laboratories as well as historians of astronomy and others.

Follow the RAS on Twitter via @royalastrosoc

Robert Massey | alfa
Further information:

More articles from Physics and Astronomy:

nachricht On Mars, sands shift to a different drum
24.05.2019 | University of Arizona

nachricht New Boost for ToCoTronics
23.05.2019 | Julius-Maximilians-Universität Würzburg

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: New studies increase confidence in NASA's measure of Earth's temperature

A new assessment of NASA's record of global temperatures revealed that the agency's estimate of Earth's long-term temperature rise in recent decades is accurate to within less than a tenth of a degree Fahrenheit, providing confidence that past and future research is correctly capturing rising surface temperatures.

The most complete assessment ever of statistical uncertainty within the GISS Surface Temperature Analysis (GISTEMP) data product shows that the annual values...

Im Focus: The geometry of an electron determined for the first time

Physicists at the University of Basel are able to show for the first time how a single electron looks in an artificial atom. A newly developed method enables them to show the probability of an electron being present in a space. This allows improved control of electron spins, which could serve as the smallest information unit in a future quantum computer. The experiments were published in Physical Review Letters and the related theory in Physical Review B.

The spin of an electron is a promising candidate for use as the smallest information unit (qubit) of a quantum computer. Controlling and switching this spin or...

Im Focus: Self-repairing batteries

UTokyo engineers develop a way to create high-capacity long-life batteries

Engineers at the University of Tokyo continually pioneer new ways to improve battery technology. Professor Atsuo Yamada and his team recently developed a...

Im Focus: Quantum Cloud Computing with Self-Check

With a quantum coprocessor in the cloud, physicists from Innsbruck, Austria, open the door to the simulation of previously unsolvable problems in chemistry, materials research or high-energy physics. The research groups led by Rainer Blatt and Peter Zoller report in the journal Nature how they simulated particle physics phenomena on 20 quantum bits and how the quantum simulator self-verified the result for the first time.

Many scientists are currently working on investigating how quantum advantage can be exploited on hardware already available today. Three years ago, physicists...

Im Focus: Accelerating quantum technologies with materials processing at the atomic scale

'Quantum technologies' utilise the unique phenomena of quantum superposition and entanglement to encode and process information, with potentially profound benefits to a wide range of information technologies from communications to sensing and computing.

However a major challenge in developing these technologies is that the quantum phenomena are very fragile, and only a handful of physical systems have been...

All Focus news of the innovation-report >>>



Industry & Economy
Event News

SEMANTiCS 2019 brings together industry leaders and data scientists in Karlsruhe

29.04.2019 | Event News

Revered mathematicians and computer scientists converge with 200 young researchers in Heidelberg!

17.04.2019 | Event News

First dust conference in the Central Asian part of the earth’s dust belt

15.04.2019 | Event News

Latest News

On Mars, sands shift to a different drum

24.05.2019 | Physics and Astronomy

Piedmont Atlanta first in Georgia to offer new minimally invasive treatment for emphysema

24.05.2019 | Medical Engineering

Chemical juggling with three particles

24.05.2019 | Life Sciences

Science & Research
Overview of more VideoLinks >>>