Astronomers have made an exciting discovery, identifying the coldest star yet known to emit radio waves. This ultracool brown dwarf is a ball of gas with a surface temperature of approximately 425 degrees Celsius, making it cooler than a typical campfire. In comparison, the Sun’s surface temperature is a scorching 5600 degrees Celsius. The team of astronomers from the University of Sydney in Australia have determined that this small and faint star is the coldest ever studied using radio astronomy.
Lead author of the study, Kovi Rose, explained that it is extremely unusual to find ultracool brown dwarfs like this producing radio emission. Typically, their dynamics do not generate the magnetic fields required for radio emissions to be detected from Earth. Therefore, the discovery of this brown dwarf emitting radio waves at such a low temperature is a significant finding. Rose further elaborated that studying ultracool brown dwarfs like this one can help improve our understanding of star evolution and the generation of magnetic fields.
The processes that lead to brown dwarfs occasionally producing radio waves are still not fully understood. While astronomers have a good grasp of how larger main sequence stars generate magnetic fields and radio emissions, less than 10 percent of brown dwarf stars produce such emissions. The rapid rotation of ultracool dwarfs is believed to play a role in generating their strong magnetic fields. When the magnetic field rotates at a different speed from the dwarf’s ionized atmosphere, it results in electrical current flows. In this particular case, the inflow of electrons to the magnetic polar region of the star, combined with its rotation, produces regularly repeating radio bursts.
Brown dwarf stars, also known as failed stars, do not possess sufficient mass to ignite nuclear fusion like other stars, including the Sun. These stars emit very little energy or light compared to other stars. Rose describes them as a missing link between the smallest stars that burn hydrogen and the largest gas giant planets like Jupiter.
The star in question, named T8 Dwarf WISE J062309.94-045624.6, is located approximately 37 light years away from Earth. It was initially discovered in 2011 by astronomers at Caltech in the United States. The star has a radius ranging from 0.65 to 0.95 that of Jupiter, making its mass somewhat uncertain. However, it is estimated to be at least four times more massive than Jupiter, but no more than 44 times more massive. For comparison, the Sun is 1,000 times more massive than Jupiter.
The analysis of this star was conducted by Rose using new data from the CSIRO ASKAP telescope in Western Australia, followed by observations from the Australia Telescope Compact Array and the MeerKAT telescope in South Africa. Professor Tara Murphy, the head of the School of Physics at the University of Sydney and co-author of the study, highlights the promising results obtained with the ASKAP telescope. She states that they have already discovered a range of interesting and unusual astronomical objects.
Moving forward, the study of radio emissions from brown dwarfs will provide valuable insights into our understanding of the stars that surround us and the potential habitability of exoplanet systems they host.
The research findings have been published in The Astrophysical Journal.
