Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

First direct measurement of the mass of an ultra-cool brown dwarf star

15.06.2004


An international team of astronomers, led by Hervé Bouy from the Max Planck Institute, Garching, Germany and the Observatoire de Grenoble, France, have for the first time measured the mass of an ultra-cool brown dwarf star. The team performed the measurements using four of the most powerful telescopes available. This is the first-ever mass measurement of an L-type star belonging to the new stellar class of very low-mass stars, discovered a few years ago. With a mass of 6.6% of the solar mass, this celestial object is a "failed" star, lying between stars and planets in the evolutionary scheme.



Making use of four of the most famous telescopes worldwide, an international team of astronomers made the first-ever direct measurement of the mass of a so-called L-type star. The star, named 2MASSW J0746425+2000321, is a binary star that was observed for four years with the ESO Very Large Telescope (Chile), the Keck and Gemini Telescopes (Hawaii), and the Hubble Space Telescope.

Precise observations of each component of the binary system were required to be able to compute their masses. As both stars are very close to each other, telescopes providing high-resolution images were needed. Additionally, observations had to be performed over a long period of time (four years) to follow the motion of both stars around each other. Very accurate measurements of the relative position of the individual components were made, so that the full orbit of the binary system could be reconstructed, as illustrated in the following picture. Once the orbit was known, the astronomers were able to compute the total mass of the system using Kepler’s laws. In addition, very precise measurements of the brightness of each star were needed to be able to compute the individual mass of each component of the system. The astronomers calculated the mass ratio of the system from these brightness measurements, using the theoretical models by G. Chabrier and collaborators (Centre de Recherche Astronomique de Lyon, France). Finally, the mass of each component could be determined.


Both stars of the binary system belong to the L stellar class that includes the lowest mass stars. This stellar class was discovered in 1997 and was added to the stellar classification that had remained unchanged for half a century. The L class is characterized by the formation of dust grains in their atmospheres, which strongly changes the shape of the spectrum. For the first time, Hervé Bouy and his team have directly measured the mass of a star from this new class of ultra-cool stars.

The more massive component of the system weighs 8.5% of the solar mass, and is likely to be a very low-mass star. Weighing 6.6% of the solar mass, the secondary star is clearly not a star, but a so-called "sub-stellar" object, a failed star that occupies an intermediate position between the lightest stars and the heaviest planets.

Theoretically foreseen for a long time, these sub-stellar objects called "brown dwarfs" were only discovered in 1995. Indirect techniques were conceived of to identify brown dwarf candidates; however, mass measurement is the only direct way to identify a star as a brown dwarf. Indeed, following stellar evolutionary models, the mass IS the criterion to determine whether a given object is a "true" star or a brown dwarf. A "true" star is heavy enough to, at some point, stabilize its temperature through fusion in its interior. For example, for 5 billion years our Sun has been burning hydrogen – it is thanks to this hydrogen fusion that the Sun shines – and it will go on burning hydrogen for 5 billion years more. A brown dwarf will never have such a stable life. Its brightness originates in the energy that remains from its birth; as this energy decreases, the brown dwarf becomes cooler and fainter. Direct mass measurements such as the one made by Bouy and his team, are a key to a better understanding of the physics of these fascinating objects.

Such mass measurements, however, are much more challenging than one could imagine. There are no means to measure the mass of a star in the Universe, except if the star belongs to a binary system. Additionally, binary brown dwarfs are often faint and close to each other: large telescopes are therefore required to perform such studies. These requirements make this research topic particularly challenging; the mass measurement performed by Hervé Bouy and his colleagues is thus a major step toward our understanding of these sub-stellar objects that occupy the gap between stars and planets.

Jennifer Martin | alfa
Further information:
http://www.edpsciences.org/journal/index.cfm?edpsname=aa&niv1=others&niv2=press_release&niv3=PR200405

More articles from Physics and Astronomy:

nachricht CCNY-Yale researchers make shape shifting cell breakthrough
12.12.2018 | City College of New York

nachricht Electronic evidence of non-Fermi liquid behaviors in an iron-based superconductor
11.12.2018 | Science China Press

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: Lethal combination: Drug cocktail turns off the juice to cancer cells

A widely used diabetes medication combined with an antihypertensive drug specifically inhibits tumor growth – this was discovered by researchers from the University of Basel’s Biozentrum two years ago. In a follow-up study, recently published in “Cell Reports”, the scientists report that this drug cocktail induces cancer cell death by switching off their energy supply.

The widely used anti-diabetes drug metformin not only reduces blood sugar but also has an anti-cancer effect. However, the metformin dose commonly used in the...

Im Focus: New Foldable Drone Flies through Narrow Holes in Rescue Missions

A research team from the University of Zurich has developed a new drone that can retract its propeller arms in flight and make itself small to fit through narrow gaps and holes. This is particularly useful when searching for victims of natural disasters.

Inspecting a damaged building after an earthquake or during a fire is exactly the kind of job that human rescuers would like drones to do for them. A flying...

Im Focus: Topological material switched off and on for the first time

Key advance for future topological transistors

Over the last decade, there has been much excitement about the discovery, recognised by the Nobel Prize in Physics only two years ago, that there are two types...

Im Focus: Researchers develop method to transfer entire 2D circuits to any smooth surface

What if a sensor sensing a thing could be part of the thing itself? Rice University engineers believe they have a two-dimensional solution to do just that.

Rice engineers led by materials scientists Pulickel Ajayan and Jun Lou have developed a method to make atom-flat sensors that seamlessly integrate with devices...

Im Focus: Three components on one chip

Scientists at the University of Stuttgart and the Karlsruhe Institute of Technology (KIT) succeed in important further development on the way to quantum Computers.

Quantum computers one day should be able to solve certain computing problems much faster than a classical computer. One of the most promising approaches is...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

VideoLinks
Industry & Economy
Event News

ICTM Conference 2019: Digitization emerges as an engineering trend for turbomachinery construction

12.12.2018 | Event News

New Plastics Economy Investor Forum - Meeting Point for Innovations

10.12.2018 | Event News

EGU 2019 meeting: Media registration now open

06.12.2018 | Event News

 
Latest News

New discoveries predict ability to forecast dementia from single molecule

12.12.2018 | Health and Medicine

CCNY-Yale researchers make shape shifting cell breakthrough

12.12.2018 | Physics and Astronomy

Pain: Perception and motor impulses arise in the brain independently of one another

12.12.2018 | Health and Medicine

VideoLinks
Science & Research
Overview of more VideoLinks >>>