Much like the planets that surround it, our own Sun also rotates around its axis. In fact, the Sun rotates, or “spins” once every 27 days. Given its size, however, space scientists note that different parts of the Sun actually spin at different rates; the equator takes some 24 days to rotate, while the poles generally need around 30 days.
Of course, the Sun isn’t the only spinning star out there. And given the information presented recently to the Monthly Notices of the Royal Astronomical Society, there are a lot of stars out there that can give the Sun a very spinny run for its money.
Named LAMOST J024048.51+195226.9, and affectionately shortened to J0240+1952, is a white dwarf located some 2,000 light-years away. This white dwarf is locked in a dance with a neighboring main sequence star (our own Sun is a main sequence star), and it is pulling stellar material away from its dance partner.
This bright stellar plasma streams away from the white dwarf like “a stream of water directed to a propeller,” according to news source EurekAlert!. As such, some of this plasma accretes around the white dwarf, rotating in and out of our view. It was this pulsing that allowed a team of researchers led by the University of Warwick (UW) astrophysicist Ingrid Pelisoli to measure just how fast it was spinning.
And frankly, it has already rotated several times by the time you are reading this part of the post, as this star rotates at a blistering pace of once every 25 seconds. It’s rotating so fast, in fact, that plasma is expected to be streaming out of the star at speeds of up to 3,000 km/s (1,864 mi/s).
“The rotation is so fast that the white dwarf must have an above average mass just to stay together and not be torn apart. It is pulling material from its companion star due to its gravitational effect, but as [it] 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,” said Pelisoli in a statement.
This fast-spinning white dwarf is the second star ever discovered that siphons off material from a main sequence partner, with some of the said material being flung off into space due to the white dwarf’s magnetic field. It joins the star AE Aquarii as the only two known propeller stars in astronomical records.
The team believes that a previous red dwarf member of the group was fed on by this white dwarf, giving it the material and the rotational speed boost. While scientists are unsure as to how J0240+1952 may have developed a magnetic field, they do believe that one is present on the star, and is the repulsive force sending the plasma away from the white dwarf at blistering speeds.
Despite this, some material still manages to get absorbed by the star at its poles, leading to accretion. This causes the star to glow brightly; this glow is what allowed astronomers to measure its rotation rate.
J0240+1952 is known as a cataclysmic variable star, in that the plasma it pulls away from its companion main sequence star may sometimes trigger “eruptions” on the white dwarf’s surface due to runaway hydrogen fusion reactions caused by the new material. The fast-spinning white dwarf may become unstable due to its own “predation” of its neighboring star, which may lead to it exploding as a Type Ia supernova.
“It’s only the second time that we have found one of these magnetic propeller systems, so we now know it’s not a unique occurrence. It establishes that the magnetic propeller mechanism is a generic property that operates in these binaries, if the circumstances are right,” said UW astrophysicist Tom Marsh who’s unrelated to the work. “The second discovery is almost as important as the first as you develop a model for the first and with the second you can test it to see if that model works. This latest discovery has shown that the model works really well, it predicted that the star had to be spinning fast, and indeed it does.”
(Read further on Modern Sciences with some of the universe’s oddities, like the “Guest Star” of 1181 and the so-called first “extragalactic” exoplanet.)
References
- Pelisoli, I., Marsh, T. R., Dhillon, V. S., Breedt, E., Brown, A. J., Dyer, M. J., Green, M. J., Kerry, P., Littlefair, S. P., Parsons, S. G., Sahman, D. I., & Wild, J. F. (2021). Found: A rapidly spinning white dwarf in LAMOST J024048.51+195226.9. ArXiv:2108.11396 [Astro-Ph]. http://arxiv.org/abs/2108.11396
- Pelisoli, I., Marsh, T. R., Dhillon, V. S., Breedt, E., Brown, A. J., Dyer, M. J., Green, M. J., Kerry, P., Littlefair, S. P., Parsons, S. G., Sahman, D. I., & Wild, J. F. (2021). Found: A rapidly spinning white dwarf in LAMOST J024048.51+195226.9. Monthly Notices of the Royal Astronomical Society: Letters, Volume 509, Issue 1, January 2022, Pages L31–L36, https://doi.org/10.1093/mnrasl/slab116
- Starr, M. (2021, November 23). Wild ‘propeller’ star smashes the record for fastest-spinning white dwarf. ScienceAlert. https://www.sciencealert.com/wild-propeller-star-has-smashed-the-record-for-the-fastest-spinning-white-dwarf
- University of Warwick. (2021, November 22). High-speed propeller star is fastest spinning white dwarf. EurekAlert! https://www.eurekalert.org/news-releases/935684
