Exactly 50 years ago Shiv Kumar has theoretically predicted the existence of Brown Dwarfs, which are the link between stars and planets. It took another 30 years until these exotic objects were actually detected by observations. The origin of these mysterious objects is still not fully understood.
A disk around a young Brown Dwarf - which ejects a Jet - similar to young recently born stars (artificial image). Axel M. Quetz, MPIA / DSS-2 (Background)
All this is reason enough for renowned experts to meet on October 21.-24. in an international conference at Ringberg Castle nearby the Tegernsee. Present will be Shiv Kumar as well as the discoverers of the first Brown Dwarfs, Ben Oppenheimer, Rafael Rebolo and Gibor Basri.
Brown Dwarfs are often called failed stars because they are too cool too sustain enough nuclear fusion to shine as the sun or other stars. On the other hand, they share many properties with giant planets, such as relatively cool atmospheres in which clouds can form. The exploration of Brown Dwarfs is, therefore, a key to understand both the formation and evolution of planets as well as those of low-mass stars.
Brown dwarfs are cool
The existence of substellar objects, which do not produce enough internal energy to shine steadily for a long time, was predicted by Shiv Kumar in 1962. The term "Brown Dwarf" was proposed in 1975 by Jill Tarter, a researcher now at the SETI Institute. However, the actual color of Brown Dwarfs is rather red or magenta. Therefore, Brown Dwarfs are not only very faint, but also radiate mainly in infrared light. It required enormous technical advancements particularly in the field of infrared detectors, to allow their discovery in the mid 90s.
One of the first Brown Dwarfs discovered, Teide 1, appeared in 1994 as an unusual red object in the camera of Rafael Rebolo of the Instituto de Astrofísica de Canarias and has been confirmed by Gibor Basri as a young Brown Dwarf. An even cooler object was found in the same year by Ben Oppenheimer and Tadashi Nakajima with the Hubble Space Telescope. They were able to even detect methane in the atmosphere of this companion of the star Gl229.
The clouds that can form in the cool atmospheres of Brown Dwarfs, can consist of e.g. iron instead of water as on earth, as Christiane Helling and Mark Marley show in their model calculations. Last year, a group of astronomers around Mike Cushing has discovered the first so-called Y-Dwarfs with the WISE-satellite. With temperatures below 300 degrees, they are the coldest, free floating celestial objects detected so far.
Origin is a mystery
Due to their low mass, a star-like formation by the gravitational collapse of gas and dust clouds is not easy to explain. Nevertheless, such a scenario seems possible to some researchers. One of many alternative formation scenarios is the ejection of "stellar embryos" out of their birth place before they can grow up to real stars.
"Some observations actually indicate a star-like formation. For example, the discovery of Brown Dwarfs that have been formed in isolation or very wide Brown Dwarf binaries - both cases which do not hint at strong dynamical interactions. Furthermore, young Brown Dwarfs were found to be surrounded by disks and to drive jets and outflows – similar to young stars", explain Viki Joergens and Thomas Henning from the Max Planck Institute for Astronomy in Heidelberg (MPIA). Their team detected this years for the first time such disks at submillimeter wavelengths with the Herschel Space Telescope and also found jets with the ESOs VLT Observatory. Such disks have been also seen in the millimeter regime with ESOs ALMA Observatory by a team including Leonardi Testi.
The conference organized by Viki Joergens and Thomas Henning from MPIA entitled "50 Years of Brown Dwarfs" will provide a lively exchange between observers and theorists, and will bring together many of the world's most renowned experts working in that field.
Contact:Dr. Viki Joergens
The size of Brown Dwarfs is determined by quantum mechanical effects and is about one Jupiter radius, when they have passed their "adolescence". Despite their name they are not really brown, but rather red or magenta.
How brown dwarfs form is still one of the main open questions in the theory of star formation. A key role to answer this question play brown dwarfs as members of binary and multiple systems. Steadily improving instrumental performance led to the discovery of companions around brown dwarfs down to planetary masses, to size (radii) and dynamical mass determinations, and to statistically significant samples of very low-mass binaries. These detailed empirical characterizations of brown dwarfs enable us to test and calibrate increasingly sophisticated models of internal structure, atmosphere, and formation of substellar objects.
There is evidence that even among the coldest Brown Dwarfs, called T-and Y-Dwarfs, binary systems were found. Their discovery might be published during this conference.
Dr. Klaus Jäger, Dr. Markus Pössel | Max-Planck-Institut
Ecology Across Borders: International conference brings together 1,500 ecologists
15.11.2017 | Gesellschaft für Ökologie e.V.
Road into laboratory: Users discuss biaxial fatigue-testing for car and truck wheel
15.11.2017 | Fraunhofer-Institut für Betriebsfestigkeit und Systemzuverlässigkeit LBF
The WHO reports an estimated 429,000 malaria deaths each year. The disease mostly affects tropical and subtropical regions and in particular the African continent. The Fraunhofer Institute for Silicate Research ISC teamed up with the Fraunhofer Institute for Molecular Biology and Applied Ecology IME and the Institute of Tropical Medicine at the University of Tübingen for a new test method to detect malaria parasites in blood. The idea of the research project “NanoFRET” is to develop a highly sensitive and reliable rapid diagnostic test so that patient treatment can begin as early as possible.
Malaria is caused by parasites transmitted by mosquito bite. The most dangerous form of malaria is malaria tropica. Left untreated, it is fatal in most cases....
The formation of stars in distant galaxies is still largely unexplored. For the first time, astron-omers at the University of Geneva have now been able to closely observe a star system six billion light-years away. In doing so, they are confirming earlier simulations made by the University of Zurich. One special effect is made possible by the multiple reflections of images that run through the cosmos like a snake.
Today, astronomers have a pretty accurate idea of how stars were formed in the recent cosmic past. But do these laws also apply to older galaxies? For around a...
Just because someone is smart and well-motivated doesn't mean he or she can learn the visual skills needed to excel at tasks like matching fingerprints, interpreting medical X-rays, keeping track of aircraft on radar displays or forensic face matching.
That is the implication of a new study which shows for the first time that there is a broad range of differences in people's visual ability and that these...
Computer Tomography (CT) is a standard procedure in hospitals, but so far, the technology has not been suitable for imaging extremely small objects. In PNAS, a team from the Technical University of Munich (TUM) describes a Nano-CT device that creates three-dimensional x-ray images at resolutions up to 100 nanometers. The first test application: Together with colleagues from the University of Kassel and Helmholtz-Zentrum Geesthacht the researchers analyzed the locomotory system of a velvet worm.
During a CT analysis, the object under investigation is x-rayed and a detector measures the respective amount of radiation absorbed from various angles....
The quantum world is fragile; error correction codes are needed to protect the information stored in a quantum object from the deteriorating effects of noise. Quantum physicists in Innsbruck have developed a protocol to pass quantum information between differently encoded building blocks of a future quantum computer, such as processors and memories. Scientists may use this protocol in the future to build a data bus for quantum computers. The researchers have published their work in the journal Nature Communications.
Future quantum computers will be able to solve problems where conventional computers fail today. We are still far away from any large-scale implementation,...
15.11.2017 | Event News
15.11.2017 | Event News
30.10.2017 | Event News
22.11.2017 | Business and Finance
22.11.2017 | Physics and Astronomy
22.11.2017 | Physics and Astronomy