Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Red Supergiant Cauldrons let off steam

17.04.2007
Steamy clouds have been observed bubbling away from four massive stars known as red supergiants. A team from Jodrell Bank, using the MERLIN array and European and Global VLBI Networks, found that the stars are actually ‘steaming’ as they enter their final death throes, driving out thick clouds of water vapour immersed in more tenuous gas.

Dr Anita Richards, who is presenting results at the RAS National Astronomy Meeting in Preston on 17th April, said, “Red supergiants lose more than half their mass before ending their lives as supernovae. Our observations show that this doesn’t happen smoothly, like an onion shedding layers. We see water vapour clouds which are over-dense, over-magnetised and rapidly accelerated away from the star. They are embedded in a cooler, more diffuse gas producing distinctive emission from hydroxyl, a break-down product of water.”

The group studied ‘maser’ emissions from the gas clouds surrounding the star: molecules in the gas amplify and emit beams of microwave radiation in much the same way as a laser produces very narrow, bright beams of light. Water emits at 1.3 cm wavelength, under hot, dense conditions (around 1000 degrees Kelvin). Hydroxyl emission at 18.0 cm can only occur from cooler, less dense gas and it was very unexpected to detect it as close to two of the stars as the water masers. The only explanation seems to be that the water masers come from clumps where the gas density is, typically, 50 times higher than the rest of the wind from the star. Supporting evidence comes from measurements of the magnetic field strength associated with the hydroxyl masers, which is much weaker than that of the adjacent water masers, as is expected if the hydroxyl environment is more diffuse.

The water vapour clouds appear to be very dusty and are accelerating faster than the surrounding gas. Only a few of these steam clouds form each stellar period (several years), filling just a few percent of the volume of the maser shell around the star, but they contain most of the mass lost by the star.

In the study, the maser emissions from the water vapour appeared to show that the clouds had a lifetime of only a few decades, although clouds were observed at distances that would have taken about a century to reach. The puzzle was solved by comparing the MERLIN results with longer-term observations from the Puschino radio telescope in Russia, which revealed individual clouds winking off and back on again due to the fickle nature of maser excitation or beaming. Dr Anita Richards said, “These observations are intriguing because, from the size of the masing shell, we estimate that the water vapour clouds take about 100 years to bubble away into interstellar space, but we can only actually ‘see’ any particular cloud for a few years.”

The group hope to follow this up by using the e-MERLIN, eVLBI and ALMA networks of radio telescopes to trace the mass loss process back to the star to discover whether star-spots, convection cells, dust formation or some other mechanism gives birth to the clumps.

Anita Heward | alfa
Further information:
http://www.ras.org.uk//index.php?option=com_content&task=view&id=1180

More articles from Physics and Astronomy:

nachricht Early opaque universe linked to galaxy scarcity
15.08.2018 | University of California - Riverside

nachricht MSU astronomers discovered supermassive black hole in an ultracompact dwarf galaxy
14.08.2018 | Lomonosov Moscow State University

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 interactive machine learning tool makes car designs more aerodynamic

Scientists develop first tool to use machine learning methods to compute flow around interactively designable 3D objects. Tool will be presented at this year’s prestigious SIGGRAPH conference.

When engineers or designers want to test the aerodynamic properties of the newly designed shape of a car, airplane, or other object, they would normally model...

Im Focus: Robots as 'pump attendants': TU Graz develops robot-controlled rapid charging system for e-vehicles

Researchers from TU Graz and their industry partners have unveiled a world first: the prototype of a robot-controlled, high-speed combined charging system (CCS) for electric vehicles that enables series charging of cars in various parking positions.

Global demand for electric vehicles is forecast to rise sharply: by 2025, the number of new vehicle registrations is expected to reach 25 million per year....

Im Focus: The “TRiC” to folding actin

Proteins must be folded correctly to fulfill their molecular functions in cells. Molecular assistants called chaperones help proteins exploit their inbuilt folding potential and reach the correct three-dimensional structure. Researchers at the Max Planck Institute of Biochemistry (MPIB) have demonstrated that actin, the most abundant protein in higher developed cells, does not have the inbuilt potential to fold and instead requires special assistance to fold into its active state. The chaperone TRiC uses a previously undescribed mechanism to perform actin folding. The study was recently published in the journal Cell.

Actin is the most abundant protein in highly developed cells and has diverse functions in processes like cell stabilization, cell division and muscle...

Im Focus: Lining up surprising behaviors of superconductor with one of the world's strongest magnets

Scientists have discovered that the electrical resistance of a copper-oxide compound depends on the magnetic field in a very unusual way -- a finding that could help direct the search for materials that can perfectly conduct electricity at room temperatur

What happens when really powerful magnets--capable of producing magnetic fields nearly two million times stronger than Earth's--are applied to materials that...

Im Focus: World record: Fastest 3-D tomographic images at BESSY II

The quality of materials often depends on the manufacturing process. In casting and welding, for example, the rate at which melts solidify and the resulting microstructure of the alloy is important. With metallic foams as well, it depends on exactly how the foaming process takes place. To understand these processes fully requires fast sensing capability. The fastest 3D tomographic images to date have now been achieved at the BESSY II X-ray source operated by the Helmholtz-Zentrum Berlin.

Dr. Francisco Garcia-Moreno and his team have designed a turntable that rotates ultra-stably about its axis at a constant rotational speed. This really depends...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

VideoLinks
Industry & Economy
Event News

Within reach of the Universe

08.08.2018 | Event News

A journey through the history of microscopy – new exhibition opens at the MDC

27.07.2018 | Event News

2018 Work Research Conference

25.07.2018 | Event News

 
Latest News

Early opaque universe linked to galaxy scarcity

15.08.2018 | Physics and Astronomy

Molecular switch detects metals in the environment

15.08.2018 | Materials Sciences

Seeing on the Quick: New Insights into Active Vision in the Brain

15.08.2018 | Life Sciences

VideoLinks
Science & Research
Overview of more VideoLinks >>>