NORTH BAY -- A team of astronomers, led by the University of Warwick in the United Kingdom, has observed a record-breaking spin rate for a confirmed white dwarf star the size of our own planet.
Published Monday in the journal , astronomers report that the white dwarf was seen completing a full rotation once every 25 seconds.
The event is being heralded as an "extremely rare" example of a magnetic propeller system, which is when a white dwarf pulls gaseous plasma from a nearby companion star and flings it into space at around 3,000 kilometres per second, according to a news release on the findings.
The team says this is only the second magnetic propeller white dwarf to be identified in more than 70 years.
Lead author Ingrid Pelisoli of the University of Warwick physics department said the white dwarf "will have completed several rotations in the short amount of time that people take to read about it,鈥� adding that it is 鈥渞eally incredible."
The astronomers say the next comparable spin rate for a confirmed white dwarf is just over 29 seconds. By comparison, it takes Earth 24 hours to complete one rotation.
"The rotation is so fast that the white dwarf must have an above average mass just to stay together and not be torn apart," Pelisoli said in the release.
"It is pulling material from its companion star due to its gravitational effect, but as that gets closer to the white dwarf the magnetic field starts to dominate. This type of gas is highly conducting and picks up a lot of speed from this process, which propels it away from the star and out into space.鈥�
Named LAMOST J024048.51+195226.9 鈥� or J0240+1952 鈥� the star observed by the Warwick team is part of a binary star system.
It is the size of Earth, but believed to be at least 200,000 times more massive.
A white dwarf is a star that has burnt up all of its fuel and shed its outer layers. From there, it goes through a process of shrinking and cooling over millions of years.
At some point, the star developed a strong magnetic field, acting as a protective barrier and causing most of the falling plasma to be propelled away from the white dwarf, with the rest flowing toward its magnetic poles, the news release said.
This plasma gathers in bright spots on the star's surface, creating pulsations in the light as it rotates in and out of view, which astronomers from Earth can then observe and use to measure the star's rotation.
The instruments used to observe the star include HiPERCAM, which is jointly operated by Warwick and the University of Sheffield, with funding from the European Research Council. It was mounted on the Gran Telescopio Canarias in La Palma in the Canary Islands, the largest functioning optical telescope in the world measuring 10 metres in diameter.
The study was led by the University of Warwick, in association with the University of Sheffield, and funded by the Science and Technology Facilities Council -- part of U.K. Research and Innovation -- and the Leverhulme Trust.
