Astronomers detect the coldest star ever observed emitting radio waves

It's burning out at a temperature of roughly 797 degrees Fahrenheit meaning it's cooler than the average campfire.
Chris Young
An artist's impression of a distant star.
An artist's impression of a distant star.

aryos / iStock 

Astronomers at the University of Sydney analyzed a small distant star and found that it is the coldest ever observed to produce emission at radio wavelength, a press statement reveals.

The 'ultracool brown dwarf,' designated T8 Dwarf WISE J062309.94−045624.6, is burning at roughly 797 degrees Fahrenheit (425 degrees centigrade) and has no nuclear fuel.

Its relatively balmy temperature, for a star, makes it cooler than the average campfire. By comparison, our Sun burns at approximately 9,930 Fahrenheit (5,600 Celcius).

The coldest star ever observed using radio astronomy

Though the star is not the coolest ever observed, it is the coldest ever analyzed using radio astronomy.

The researchers behind the analysis, who published their findings in The Astrophysical Journal, believe the new discovery will help us better understand the evolution of stars and the potential for habitability in systems surrounding these types of stars.

Though the star was originally discovered in 2011 by astronomers at Caltech in the US, the new analysis was conducted using new data collected by the CSIRO ASKAP telescope in Western Australia as well as follow-up observations from the Australia Telescope Compact Array near Narrabri in NSW and the MeerKAT telescope in South Africa.

"It's very rare to find ultracool brown dwarf stars like this producing radio emission," explained Kovi Rose, lead author of the study. "That’s because their dynamics do not usually produce the magnetic fields that generate radio emissions detectable from Earth."

"Finding this brown dwarf producing radio waves at such a low temperature is a neat discovery," Rose continued. "Deepening our knowledge of ultracool brown dwarfs like this one will help us understand the evolution of stars, including how they generate magnetic fields."

The star in question is located roughly 37 light-years from Earth. It has a radius between 0.65 and 0.95, that of Jupiter, but it is believed to have somewhere in the region of four to 44 times the mass. As a point of reference, the Sun is 1,000 times more massive than Jupiter.

Analyzing a mysterious distant star

Astronomers don't fully understand how brown dwarf stars form. They essentially blur the line between planets and stars, and they could form like a planet, by the accretion of material in a protoplanetary disk, or like a star, by the contraction of gas.

What's more, fewer than 10 percent of observed brown dwarf stars produce radio emissions, and astronomers aren't completely sure why. By contrast, they do know how larger "main sequence" stars like the Sun generate magnetic fields and radio emissions.

Some astronomers believe the rapid rotation of ultracool dwarfs may play a part, as the magnetic field rotates at a different speed to the dwarf's ionized atmosphere, creating electrical current flows.

Astronomers detect the coldest star ever observed emitting radio waves
An artist's impression of a brown dwarf star.

In the case of T8 Dwarf WISE J062309.94−045624.6, the researchers believe the radio waves are being produced by electrons flowing to the magnetic polar region of the star. This, as well as the rotation of the brown dwarf star, produces regular radio bursts.

Brown dwarf stars are not large enough to ignite the nuclear fusion reaction associated with stars like our Sun. In fact, NASA points out on its website that these stars "muddy a clear distinction between stars and planets, throwing established understanding of those bodies, and theories of their formation, into question."

The team behind the new analysis echoes this point. "These stars are a kind of missing link between the smallest stars that burn hydrogen in nuclear reactions and the largest gas giant planets, like Jupiter," Rose explained. As such, analyzing these mysterious stars will help us better understand the evolution of the cosmos and the role they play throughout the universe.

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