Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Glasgow astronomers explain hot star disks

01.11.2002


Astronomers have been puzzled for decades as to how the rings of hot gas surrounding certain types of star are formed. Now a team of scientists from the Universities of Glasgow and Wisconsin believe they have found the answer. The team studied a type of young, hot star, known as a "Be star", that has a disk of glowing gas around it, similar to the rings surrounding Saturn. Until now, no one has been able to account for how these rings form but in a paper published this month*, the team suggest an answer.


Artist’s impression of a Be Star



The gas ring surrounding a Be Star may appear and then disappear, possibly reforming at a later time. Material in the disk is attracted back towards the star by the pull of gravity, but if it has enough energy it can escape into space, contributing to the stellar wind.

The new theory reveals why this material is held in a disk at some distance from the star instead of either being pulled closer or flying away into space.


Deborah Telfer of Glasgow University explains
"Our model relies on the existence of a magnetic field around Be stars producing a ‘Magnetically Torqued Disk’. Magnetic field lines channel stellar wind material leaving the surface of the star down towards the equatorial plane. A disk then forms in the region where particles have sufficient angular velocity to balance gravity. In the outer regions, the weaker magnetic field lines should burst open allowing particles to form part of the general stellar wind."

Previously, the Wind Compressed Disk Model (Bjorkman and Cassinelli, 1993) was regarded as one of the most successful explanations of circumstellar disks. However, it predicts disks that are out-flowing (i.e. the material moves from the star to the disk and then away into space) and expanding. Yet Be stars are observed to have circumstellar Keplerian disks, meaning that the disks are supported against gravity by rotation rather than gas or radiation pressure.

Deborah has been working with Joseph Cassinelli of Wisconsin on the new model for Be star disks and they are delighted at the success of their results.

These suggest that only a narrow range of types of star would form a detectable Magnetically Torqued Disk and be seen as Be stars.

Heavier stars would require an unreasonably large magnetic field while lighter stars would produce disks too small to be detected. More work is needed to explain every aspect of observational evidence but we may finally be reaching an understanding of what
produces these Saturn-like stars.

Julia Maddock | alfa

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 proton record: Researchers measure magnetic moment with greatest possible precision

High-precision measurement of the g-factor eleven times more precise than before / Results indicate a strong similarity between protons and antiprotons

The magnetic moment of an individual proton is inconceivably small, but can still be quantified. The basis for undertaking this measurement was laid over ten...

Im Focus: Frictional Heat Powers Hydrothermal Activity on Enceladus

Computer simulation shows how the icy moon heats water in a porous rock core

Heat from the friction of rocks caused by tidal forces could be the “engine” for the hydrothermal activity on Saturn's moon Enceladus. This presupposes that...

Im Focus: Nanoparticles help with malaria diagnosis – new rapid test in development

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....

Im Focus: A “cosmic snake” reveals the structure of remote galaxies

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...

Im Focus: Visual intelligence is not the same as IQ

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...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

Ecology Across Borders: International conference brings together 1,500 ecologists

15.11.2017 | Event News

Road into laboratory: Users discuss biaxial fatigue-testing for car and truck wheel

15.11.2017 | Event News

#Berlin5GWeek: The right network for Industry 4.0

30.10.2017 | Event News

 
Latest News

IceCube experiment finds Earth can block high-energy particles from nuclear reactions

24.11.2017 | Physics and Astronomy

A 'half-hearted' solution to one-sided heart failure

24.11.2017 | Health and Medicine

Heidelberg Researchers Study Unique Underwater Stalactites

24.11.2017 | Earth Sciences

VideoLinks
B2B-VideoLinks
More VideoLinks >>>