Gregg Hallinan of the National University of Ireland, Galway, who is presenting the discovery at the RAS National Astronomy Meeting in Preston on 18th April, said, “Brown dwarfs tend to be seen as a bit boring – the cinders of the galaxy. Our research shows that these objects can be fascinating and dynamic systems, and may be the key to unlocking this long-standing mystery of how pulsars produce radio emissions.”
Since the discovery of pulsars forty years ago, astronomers have been trying to understand how the rotating neutron stars produce their flashing radio signals. Although there have been many attempts to describe how they produce the extremely bright radio emissions, the vast magnetic field strengths of pulsars and the relativistic speeds involved make it extremely difficult to model. Brown dwarfs are now the second class of stellar object observed to produce this kind of powerful, amplified (coherent) radio signal at a persistent level. The emissions from the brown dwarfs appear to be very similar to those observed from pulsars, but the whole system is on a much slower and smaller scale, so it is much easier to decipher exactly what is going on. Importantly, the mechanisms for producing the radio emissions in brown dwarfs are well understood, as they are almost identical to the processes that produce radio emissions from planets.
Hallinan said, “It looks like brown dwarfs are the missing step between the radio emissions we see generated at Jupiter and those we observe from pulsars”.
Jupiter’s volcanic moon, Io, is a source of electrically charged gas that is accelerated by the planet’s magnetic field and causes powerful radio laser, or maser, emissions. The radiation can be so intense that Jupiter frequently outshines the Sun as a source of energy at radio wavelengths. For some time, scientists have thought that there may be similarities between this type of maser emission and pulsars’ lighthouse-like beams of radio waves. Observations of the brown dwarf, TVLM 513, using the Very Large Array (VLA) radio telescope, may provide the first direct evidence for that link.
The group observed the brown dwarf over a period of 10 hours at two different frequencies. In both cases, a bright flash was observed every 1.96 hours.
As yet, the processes controlling the radio flashes from TVLM 513 are still unclear. There is no evidence of a binary system, so interaction of the magnetosphere with a stellar wind from a nearby star seems an unlikely cause, nor is there any sign of an orbiting planet that could produce a scenario like that of Jupiter and Io. However, rapid rotation is also thought to be a source of electron acceleration for a component of Jupiter’s maser emission and this may also be the main source of TVLM 513’s radio flashes.
The group is now planning a large survey of all the known brown dwarfs in the solar neighbourhood to find out how many are radio sources and how many of those are pulsing. If a large fraction of brown dwarfs are found to pulse, it could prove a key method of detection for these elusive objects.
Anita Heward | alfa
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17.12.2018 | Universität Basel
Researchers from the University of Basel have reported a new method that allows the physical state of just a few atoms or molecules within a network to be controlled. It is based on the spontaneous self-organization of molecules into extensive networks with pores about one nanometer in size. In the journal ‘small’, the physicists reported on their investigations, which could be of particular importance for the development of new storage devices.
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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...
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...
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