A comparison of the relative size of planets and brown dwarfs to the size of our sun. Credit: https://student.societyforscience.org/article/failed-%E2%80%98star%E2%80%99-found-sun%E2%80%99s-backyard
Despite being discovered 20 yrs ago, little is known about brown dwarfs – notably why they fail to grow into stars. Part of the answer probably lies in the physics of how dense plasmas merge inside them. Now researchers, led by the York Plasma Institute at the University of York and the UK’s Science and Technology Facilities Council’s (STFC) Central Laser
Facility, have created “lumps” of plasma to recreate the conditions similar to those found deep inside brown dwarfs. To do this they used the world’s most powerful lasers, STFC’s Vulcan Petawatt at Oxfordshire laser laboratory, to create the first test of resistivity and viscosity found in brown dwarfs.
Brown dwarfs bridge the gap between very low mass stars and planets and share characteristics with both. Despite being numerous across the immensity of space, these little “starlets” are hard to spot because they are small and cool in temperature so tend to be faint and difficult to record.
But by measuring the xrays emitted from these objects, they were able to build up a profile of how dense plasmas form inside brown dwarfs.
This artist’s conception illustrates the brown dwarf named 2MASSJ22282889-431026. NASA’s Hubble and Spitzer space telescopes observed the object to learn more about its turbulent atmosphere. Brown dwarfs are more massive and hotter than planets but lack the mass required to become sizzling stars. Their atmospheres can be similar to the giant planet Jupiter’s. Spitzer and Hubble simultaneously observed the object as it rotated every 1.4 hours. The results suggest wind-driven, planet-size clouds. Credit: NASA
The results pave the way towards furthering our understanding of these celestial objects. Professor Nigel Woolsey, from the Department of Physics at York, said: “Brown dwarfs are really difficult to observe because they are cool and our atmosphere absorbs the emissions from cool objects. “One of the issues you have in brown dwarfs with dense matter is how this material comes together and how hot it gets.
“We think, but we don’t know because we can’t see them, but we think there are lots of brown dwarfs about. “There is a suggestion there is at least as many brown dwarfs as there are stars. There’s more than a billion stars in our galaxy.” Dr Nicola Booth added: “The Vulcan Petawatt laser is one of the few places on Earth where we can produce conditions close to those at the centre of a brown dwarf. “We hope that with the predicted future observations of brown dwarfs, our experiments can help with the understanding of how energy is transported in these ‘starlets’.”
http://www.york.ac.uk/news-and-events/news/2015/research/browndwarfs-laser-physics/
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