Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Stellar Still Births: Researchers reveal brown dwarfs as third class of celestial bodies after stars and planets

22.08.2008
The systematics of celestial bodies apparently needs to be revised. Researchers at the Argelander Institute of Astronomy of the University of Bonn have discovered that brown dwarfs need to be treated as a separate class in addition to stars and planets.

To date they had been merely regarded as stars which were below normal size. However, they may well be stellar ‘miscarriages’. The astronomers are publishing their results in the journal Monthly Notices of the Royal Astronomical Society. A preview can be seen at http://arxiv.org/abs/0808.2644.

Brown dwarfs (or BDs) are what scientists call objects which populate the galaxies apart from the stars. Unlike the latter, they cannot develop high-yield hydrogen fusion as in the interior of our sun due to their low mass (less than about 8% of the sun’s mass). But in addition to this brown dwarfs and stars also seem to be different in their ‘mating behaviour’.

Stars often occur in pairs, which dance around each other. The intimacy which this dance involves, however, varies a great deal: sometimes the gap is smaller than one radius of the Earth’s orbit (also known as Astronomical Unit or AU). However, the two partners can also keep apart by as much as many thousands of AUs. ‘Things are different with brown dwarfs,’ astrophysicist Ingo Thies of the Bonn Argelander Institute of Astronomy explains. ‘The orbital radiuses of BD pairs are cut off above about 15 AUs; BD pairs with greater distances are the exception.’

What is more, there are hardly any mixed pairs consisting of suns and brown dwarfs – far fewer than expected. This phenomenon is also known as brown dwarf desert. ‘According to the classical model there ought not to be these differences,’ Professor Pavel Kroupa of the Argelander Institute explains. ‘According to this both brown dwarfs and stars ought to emerge from interstellar clouds of gas which become concentrated because of the attraction of their mass. But if this was the case, these celestial bodies should behave in similar ways.’

Despite this contradiction the astronomic community has previously stuck to the theory of a joint origin. However, Ingo Thies and Pavel Kroupa have now shown empirically for the first time that brown dwarfs must be seen as a class of objects which is separate from the stars. ‘For this we analysed the masses of newly born stars,’ Ingo Thies explains. ‘This revealed a jump in the distribution of mass which makes the division in the stellar population apparent.’

Death of an embryonic star

But how are brown dwarfs born? As long ago as 2001 the Danish researcher Bo Reipurth, Britain’s Cathie Clarke and the Spanish astronomer Eduardo Delgado-Donate had the idea that brown dwarfs could be interpreted as stellar ‘miscarriages’: a system consisting of three embryonic stars disintegrates due to the mutual attraction of masses, and the lightest object is catapulted out of the system. The physical mechanism itself has long been known: even the US light space probes Pioneer and Voyager were hurled off onto their voyage of no return by the planet’s gravity.

Another possibility would be that brown dwarfs form in the outermost regions of emergent stars and become separated from them. This can, for example, occur as the result of a close encounter with a third star. Since almost all stars are born in star clusters, such encounters are not unusual. It is also possible that both scenarios of cosmic miscarriages take place.

Both theories predict that brown dwarfs can only emerge at the birth of stars – similar to the situation with planets, incidentally. Thus there are presumably three quite different celestial bodies: planets, brown dwarfs and stars.

Prof. Dr. Pavel Kroupa | alfa
Further information:
http://www.uni-bonn.de

More articles from Physics and Astronomy:

nachricht First Juno science results supported by University of Leicester's Jupiter 'forecast'
26.05.2017 | University of Leicester

nachricht Measured for the first time: Direction of light waves changed by quantum effect
24.05.2017 | Vienna 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 the immune system be boosted against Staphylococcus aureus by delivery of messenger RNA?

Staphylococcus aureus is a feared pathogen (MRSA, multi-resistant S. aureus) due to frequent resistances against many antibiotics, especially in hospital infections. Researchers at the Paul-Ehrlich-Institut have identified immunological processes that prevent a successful immune response directed against the pathogenic agent. The delivery of bacterial proteins with RNA adjuvant or messenger RNA (mRNA) into immune cells allows the re-direction of the immune response towards an active defense against S. aureus. This could be of significant importance for the development of an effective vaccine. PLOS Pathogens has published these research results online on 25 May 2017.

Staphylococcus aureus (S. aureus) is a bacterium that colonizes by far more than half of the skin and the mucosa of adults, usually without causing infections....

Im Focus: A quantum walk of photons

Physicists from the University of Würzburg are capable of generating identical looking single light particles at the push of a button. Two new studies now demonstrate the potential this method holds.

The quantum computer has fuelled the imagination of scientists for decades: It is based on fundamentally different phenomena than a conventional computer....

Im Focus: Turmoil in sluggish electrons’ existence

An international team of physicists has monitored the scattering behaviour of electrons in a non-conducting material in real-time. Their insights could be beneficial for radiotherapy.

We can refer to electrons in non-conducting materials as ‘sluggish’. Typically, they remain fixed in a location, deep inside an atomic composite. It is hence...

Im Focus: Wafer-thin Magnetic Materials Developed for Future Quantum Technologies

Two-dimensional magnetic structures are regarded as a promising material for new types of data storage, since the magnetic properties of individual molecular building blocks can be investigated and modified. For the first time, researchers have now produced a wafer-thin ferrimagnet, in which molecules with different magnetic centers arrange themselves on a gold surface to form a checkerboard pattern. Scientists at the Swiss Nanoscience Institute at the University of Basel and the Paul Scherrer Institute published their findings in the journal Nature Communications.

Ferrimagnets are composed of two centers which are magnetized at different strengths and point in opposing directions. Two-dimensional, quasi-flat ferrimagnets...

Im Focus: World's thinnest hologram paves path to new 3-D world

Nano-hologram paves way for integration of 3-D holography into everyday electronics

An Australian-Chinese research team has created the world's thinnest hologram, paving the way towards the integration of 3D holography into everyday...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

Marine Conservation: IASS Contributes to UN Ocean Conference in New York on 5-9 June

24.05.2017 | Event News

AWK Aachen Machine Tool Colloquium 2017: Internet of Production for Agile Enterprises

23.05.2017 | Event News

Dortmund MST Conference presents Individualized Healthcare Solutions with micro and nanotechnology

22.05.2017 | Event News

 
Latest News

How herpesviruses win the footrace against the immune system

26.05.2017 | Life Sciences

Water forms 'spine of hydration' around DNA, group finds

26.05.2017 | Life Sciences

First Juno science results supported by University of Leicester's Jupiter 'forecast'

26.05.2017 | Physics and Astronomy

VideoLinks
B2B-VideoLinks
More VideoLinks >>>