Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Astronomers show that low-mass stars in binary stars appear to behave like high-mass, evolved stars

26.05.2003


Astronomers Steve Howell of the University of California, Riverside and Thomas E. Harrison and Heather Osborne of New Mexico State University have found from their observations of over a dozen mass-losing stars in ’cataclysmic variables’ that most of the secondary stars do not appear to be normal main sequence stars in terms of their apparent abundances. To various degrees, each star seems to have low to no carbon and other odd mixtures of elements such as sodium and calcium, the astronomers announced today at the American Astronomical Society meeting in Nashville, Tenn.


An artist’s conception of a cataclysmic variable. Cataclysmic variables are binary stars consisting of a white dwarf primary and a lower mass secondary star.
(Artist: Mark Garlick, http://www.space-art.co.uk/, mark@space-art.co.uk)



(A main sequence star is a star that is in its normal state, such as the sun. These stars have well-defined relations between luminosity, temperature, size and mass.)

"Cataclysmic variables are binary stars consisting of a white dwarf primary and a lower mass secondary star," explained Howell. A binary star system consists of two stars orbiting about their common center of mass and held together by their mutual gravitational attraction. A white dwarf is a star that has exhausted all its nuclear fuel and has collapsed to a very small size, about the size of the Earth.


Howell further explained that the high gravity of the white dwarf pulls matter off the lower-mass, but larger secondary star. This material often forms a disk around the white dwarf. The orbital periods of these binaries are short, typically ranging from approximately 12 hours to 80 minutes. "Cataclysmic variables are very small systems," he said. "The entire binary would completely fit inside our sun."

For their research, the three astronomers used telescopes to obtain spectral observations of mass-losing stars in cataclysmic variables. "Our findings suggest that the normal idea that ’main sequence’ rules apply to the mass-losing stars appears not to be the case," said Howell. "Furthermore, the observed abundance patterns are consistent with stellar material formed by a process called CNO or carbon-nitrogen-oxygen burning, which is only thought to occur in stars with masses greater than those of the mass-losing stars.

The research, funded by the National Science Foundation, was performed in the past two years using telescopes located at the Kitt Peak National Observatory, near Tucson, Ariz., and on Mauna Kea, Hawaii, using the NASA infrared telescope (IRTF) and the United Kingdom infrared telescope (UKIRT).

Additional contacts:
Steve Howell, steve.howell@ucr.edu
Thomas Harrison, tharriso@nmsu.edu

Iqbal Pittalwala | UC Riverside
Further information:
http://www.newsroom.ucr.edu/cgi-bin/display.cgi?id=595
http://www.igpp.ucr.edu/
http://www.cnas.ucr.edu/

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: LaserTAB: More efficient and precise contacts thanks to human-robot collaboration

At the productronica trade fair in Munich this November, the Fraunhofer Institute for Laser Technology ILT will be presenting Laser-Based Tape-Automated Bonding, LaserTAB for short. The experts from Aachen will be demonstrating how new battery cells and power electronics can be micro-welded more efficiently and precisely than ever before thanks to new optics and robot support.

Fraunhofer ILT from Aachen relies on a clever combination of robotics and a laser scanner with new optics as well as process monitoring, which it has developed...

Im Focus: The pyrenoid is a carbon-fixing liquid droplet

Plants and algae use the enzyme Rubisco to fix carbon dioxide, removing it from the atmosphere and converting it into biomass. Algae have figured out a way to increase the efficiency of carbon fixation. They gather most of their Rubisco into a ball-shaped microcompartment called the pyrenoid, which they flood with a high local concentration of carbon dioxide. A team of scientists at Princeton University, the Carnegie Institution for Science, Stanford University and the Max Plank Institute of Biochemistry have unravelled the mysteries of how the pyrenoid is assembled. These insights can help to engineer crops that remove more carbon dioxide from the atmosphere while producing more food.

A warming planet

Im Focus: Highly precise wiring in the Cerebral Cortex

Our brains house extremely complex neuronal circuits, whose detailed structures are still largely unknown. This is especially true for the so-called cerebral cortex of mammals, where among other things vision, thoughts or spatial orientation are being computed. Here the rules by which nerve cells are connected to each other are only partly understood. A team of scientists around Moritz Helmstaedter at the Frankfiurt Max Planck Institute for Brain Research and Helene Schmidt (Humboldt University in Berlin) have now discovered a surprisingly precise nerve cell connectivity pattern in the part of the cerebral cortex that is responsible for orienting the individual animal or human in space.

The researchers report online in Nature (Schmidt et al., 2017. Axonal synapse sorting in medial entorhinal cortex, DOI: 10.1038/nature24005) that synapses in...

Im Focus: Tiny lasers from a gallery of whispers

New technique promises tunable laser devices

Whispering gallery mode (WGM) resonators are used to make tiny micro-lasers, sensors, switches, routers and other devices. These tiny structures rely on a...

Im Focus: Ultrafast snapshots of relaxing electrons in solids

Using ultrafast flashes of laser and x-ray radiation, scientists at the Max Planck Institute of Quantum Optics (Garching, Germany) took snapshots of the briefest electron motion inside a solid material to date. The electron motion lasted only 750 billionths of the billionth of a second before it fainted, setting a new record of human capability to capture ultrafast processes inside solids!

When x-rays shine onto solid materials or large molecules, an electron is pushed away from its original place near the nucleus of the atom, leaving a hole...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

“Lasers in Composites Symposium” in Aachen – from Science to Application

19.09.2017 | Event News

I-ESA 2018 – Call for Papers

12.09.2017 | Event News

EMBO at Basel Life, a new conference on current and emerging life science research

06.09.2017 | Event News

 
Latest News

Fraunhofer ISE Pushes World Record for Multicrystalline Silicon Solar Cells to 22.3 Percent

25.09.2017 | Power and Electrical Engineering

Usher syndrome: Gene therapy restores hearing and balance

25.09.2017 | Health and Medicine

An international team of physicists a coherent amplification effect in laser excited dielectrics

25.09.2017 | Physics and Astronomy

VideoLinks
B2B-VideoLinks
More VideoLinks >>>