An adorable pair of white dwarf stars spiraling closer to each other are the latest addition to a promising gravitational wave source that astronomers may discover in the near future.
Of course, epic stellar mergers are the ultimate fate of many binaries when stars get too close to their partners. However, this new discovery – called J2322 + 0509 – is special. That's why.
White dwarfs are the remnants of stellar cores left behind after stars like our Sun have run out of fuel. J2322 + 0509 is two helium-core white dwarfs in close orbit, but they do not share any matter (unlike one star absorbing material from another).
In fact, J2322 + 0509 has an orbital period of 20 minutes and one second, which is one of the shortest periods of any single binary star known. During this short period of time, each star in the binary system completes the full orbit of the other.
That's about three times longer than the current record holder – two stars orbiting each other in less than seven minutes – but still an incredible characteristic, and one that generates even more amazing phenomena.
The theory predicts that double white dwarfs with particularly close orbits, such as J2322 + 0509, could become the source of gravitational waves: invisible ripples in the fabric of spacetime that are generated when extremely massive objects change their speed.
Gravitational waves were first detected in 2015. The Gravitational Wave Observatory (LIGO) discovered them from the collision of two black holes – an event that happened about 1.3 billion years ago.
But mergers of black holes are not the only thing that can create gravitational waves. General relativity predicts that these powerful vibrations in the fabric of the universe could also come from other sources, including the spinning of neutron stars, supernova explosions, and, yes, the spiral motion of dense white dwarfs in binaries as they rotate fast and close – just like J2322 + 0509.
The orbit of this pair of objects is approaching. Steam loses energy due to the emitted gravitational waves; in 6 or 7 million years they will merge into one more massive white dwarf.
The discovery serves as a basis for future experiments so that astronomers can find more of these stars and determine their true number.
The results will be published in The Astrophysical Journal Letters.
Sources: Photo: (M. Weiss)
