It’s the coolest star in town.
It may not be the shiniest, but for one brown dwarf star that doesn’t matter. Astronomers at the University of Sydney have just found the coldest star on record to emit radio waves.
At a mere 425 degrees Celcius (797 Fahrenheit), this little ball of gas is cooler than a typical campfire. The Sun, meanwhile, burns nuclear fuel to reach a whopping 5,600 degrees Celcius (10,112 Fahrenheit).
“Finding this brown dwarf producing radio waves at such a low temperature is a neat discovery,” said lead author Kovi Rose, PhD candidate at Sydney’s School of Physics.
The discovery, published in The Astrophysical Journal, is unusual. According to Rose, “It’s very rare to find ultracool brown dwarf stars like this producing radio emission.
“That’s because their dynamics do not usually produce the magnetic fields that generate radio emissions detectable from Earth.”
Radio waves can teach us a lot about the composition, structure and motion of astronomical objects. However, fewer than 10 per cent of brown dwarfs produce radio emissions.
The Australian scientists hope that their discovery will deepen existing knowledge of ultracool brown dwarfs, including how they evolve and generate magnetic fields.
The star, known (to some) as T8 Dwarf WISE J062309.94−045624.6, is located about 37 light years from Earth. Its radius is smaller than Jupiter’s – another rare find for a brown dwarf star – but is between 4 to 44 times more massive than our gas giant. It was originally discovered in 2011 by US astronomers, but using infrared spectroscopy rather than radio.
The name ‘brown dwarf’ comes from the fact that these stars give off very little light – as well as the fact they are not large enough to ignite and sustain nuclear fusion in the same way that stars like our Sun do.
This discovery is just one in the beginning of a series of unusual astronomical objects detected using new data from the CSIRO ASKAP telescope in Western Australia. The ASKAP is a radio telescope which can map the sky extremely quickly.
Co-author Professor Tara Murphy said: “As we open this window on the radio sky, we will improve our understanding of the stars around us, and the potential habitability of exoplanet systems they host.”
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