Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

How stars grow into heavyweights

04.11.2015

Astronomers find a stable disk around a young, massive sun

Stars count lightweights and heavyweights among their number. All are born in clouds of gas and dust, but the more massive a baby star, the earlier nuclear fusion ignites in its core. And the radiation pressure produced here should really purge its surroundings and thus prevent the infall of matter which will allow the star to grow bigger. Some stars nevertheless manage to reach masses of more than a hundred times that of our Sun. How is this possible?


A star puts on weight: This artist’s impression shows the disk of gas and dust around the massive sun AFGL 4176.

© K. G. Johnston and ESO

Astronomers have believed for some time that disks around the infant stars play an important role in this process. A team of researchers including astronomers from the Heidelberg Max Planck Institute for Astronomy have now discovered such a stable structure around one of the most massive, newly forming stars in our galaxy.

The team headed by Katharine Johnston from the University of Leeds, and including the Max Planck astronomers Thomas Robitaille, Henrik Beuther, Hendrik Linz and Roy van Boekel, turned their sights on the object with catalogue number AFGL 4176. It is a very massive star in the southern constellation known as Centaurus, around 14,000 light years from Earth.

The star is in the process of being born, which is why its immediate environment is concealed within an envelope of gas and dust. The scientists observed the star in the millimetre and submillimetre range with the ALMA observatory of the European Southern Observatory (ESO), however – and looked behind the veil and into the interior of the envelope. They detected a disk-like, rotating structure.

To confirm this observation, the astronomers arranged a kind of identification parade: first they simulated more than 10,000 model disks with different properties. They then compared these images and spectra with the data obtained from nature. The best agreement was for a stable disk, where the gravitational effects of both the star and the disk material are important.

The radius of the disk surrounding AFGL 4176 is roughly 2000 times the average distance between the Earth and the Sun. The total mass is 12 solar masses – this corresponds to just under half the weight of the star itself, which is roughly 25 solar masses. The disk rotates around the star in a similar way to the planets around our Sun: the gas in the inner regions moves faster than that in the outer ones and obeys the laws discovered by Johannes Kepler at the beginning of the 17th century.

These Keplerian disks could play a key role in the growth of massive stars and particularly explain how enough additional matter can accrete despite the substantial radiation pressure exerted by the young star. One factor is that a stable disk of this type can direct enormous amounts of matter onto the nascent star; another is that it presents a very narrow profile to the radiation pressure and thus a much smaller area of attack than gas which surrounds the star like a spherical shell.

Astronomers had previously been unable to detect stable disks around the most massive stellar embryos (O-type stars) with certainty. It was therefore unclear whether these disks were possible explanations at all.

The observations by Katharine Johnston and her colleagues, in contrast, show that at least one of the most massive stars can be formed in the same way as its less massive relatives: through mechanisms which are the same as those of less massive stars despite differences in scales and in timing; and with matter which is funnelled onto the growing infant star by a Keplerian disk.

The high quality of the ALMA observations raises expectations that it will also be possible to clarify further important, unanswered questions about the formation of massive stars. The astronomers hope for information about one feature in particular: very massive stars are nearly always members of twin or multiple star systems. High-resolution images of the innermost regions in the early phases of star birth could show directly how the precursors of the different components of such a system form.


Contact

Dr. Markus Pössel
Max Planck Institute for Astronomy, Heidelberg
Phone: +49 6221 528-261

Email: poessel@mpia.de

 
Dr. Henrik Beuther
Max Planck Institute for Astronomy, Heidelberg
Phone: +49 6221 528-447

Email: beuther@mpia.de

Dr. Thomas Robitaille
Max Planck Institute for Astronomy, Heidelberg
Phone: +49 6221 528-395

Email: robitaille@mpia.de


Original publication
Johnston et al.
A Keplerian-like disk around the forming O-type star AFGL 4176
Astrophysical Journal Letters, 29 October 2015

Source

Dr. Markus Pössel | Max Planck Institute for Astronomy, Heidelberg
Further information:
https://www.mpg.de/9723445/massive-star

More articles from Physics and Astronomy:

nachricht Ultra-compact phase modulators based on graphene plasmons
27.06.2017 | ICFO-The Institute of Photonic Sciences

nachricht Smooth propagation of spin waves using gold
26.06.2017 | Toyohashi University of Technology

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: Can we see monkeys from space? Emerging technologies to map biodiversity

An international team of scientists has proposed a new multi-disciplinary approach in which an array of new technologies will allow us to map biodiversity and the risks that wildlife is facing at the scale of whole landscapes. The findings are published in Nature Ecology and Evolution. This international research is led by the Kunming Institute of Zoology from China, University of East Anglia, University of Leicester and the Leibniz Institute for Zoo and Wildlife Research.

Using a combination of satellite and ground data, the team proposes that it is now possible to map biodiversity with an accuracy that has not been previously...

Im Focus: Climate satellite: Tracking methane with robust laser technology

Heatwaves in the Arctic, longer periods of vegetation in Europe, severe floods in West Africa – starting in 2021, scientists want to explore the emissions of the greenhouse gas methane with the German-French satellite MERLIN. This is made possible by a new robust laser system of the Fraunhofer Institute for Laser Technology ILT in Aachen, which achieves unprecedented measurement accuracy.

Methane is primarily the result of the decomposition of organic matter. The gas has a 25 times greater warming potential than carbon dioxide, but is not as...

Im Focus: How protons move through a fuel cell

Hydrogen is regarded as the energy source of the future: It is produced with solar power and can be used to generate heat and electricity in fuel cells. Empa researchers have now succeeded in decoding the movement of hydrogen ions in crystals – a key step towards more efficient energy conversion in the hydrogen industry of tomorrow.

As charge carriers, electrons and ions play the leading role in electrochemical energy storage devices and converters such as batteries and fuel cells. Proton...

Im Focus: A unique data centre for cosmological simulations

Scientists from the Excellence Cluster Universe at the Ludwig-Maximilians-Universität Munich have establised "Cosmowebportal", a unique data centre for cosmological simulations located at the Leibniz Supercomputing Centre (LRZ) of the Bavarian Academy of Sciences. The complete results of a series of large hydrodynamical cosmological simulations are available, with data volumes typically exceeding several hundred terabytes. Scientists worldwide can interactively explore these complex simulations via a web interface and directly access the results.

With current telescopes, scientists can observe our Universe’s galaxies and galaxy clusters and their distribution along an invisible cosmic web. From the...

Im Focus: Scientists develop molecular thermometer for contactless measurement using infrared light

Temperature measurements possible even on the smallest scale / Molecular ruby for use in material sciences, biology, and medicine

Chemists at Johannes Gutenberg University Mainz (JGU) in cooperation with researchers of the German Federal Institute for Materials Research and Testing (BAM)...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

Plants are networkers

19.06.2017 | Event News

Digital Survival Training for Executives

13.06.2017 | Event News

Global Learning Council Summit 2017

13.06.2017 | Event News

 
Latest News

Touch Displays WAY-AX and WAY-DX by WayCon

27.06.2017 | Power and Electrical Engineering

Drones that drive

27.06.2017 | Information Technology

Ultra-compact phase modulators based on graphene plasmons

27.06.2017 | Physics and Astronomy

VideoLinks
B2B-VideoLinks
More VideoLinks >>>