In 2015, astronomers discovered something strange. It was a white dwarf star, 570 light years from Earth, with a kind of repetitive twinkling.
Its luminosity dropped to different levels, which was repeated for 4.5-5 hours; and the atmosphere was polluted by elements commonly found on rocky planets.
It didn't take long for astronomers to figure out the cause of this flicker. The dead star's gravity was in the process of crushing and devouring bodies in orbit around it, a process known as tidal destruction.
The star is called WD 1145 + 017 and is now being used as a proof of concept for a new field of planetary exploration, reconstructing planetary bodies to understand what they were and how they died.
Astronomers from the United States and the United Kingdom refer to this area as necroplanetology.
Their analysis of WD 1145 + 017 has been accepted for publication in the Astrophysical Journal and is available on arXiv.
The researchers say the study could be applied to future discoveries like the white dwarf system to piece together information about how planets die while orbiting various types of dead stars.
Although white dwarfs emit a lot of material, in a series of violent thermonuclear explosions, planets may somehow survive this process. Not only did we find planets orbiting white dwarfs, we also found elements in the atmospheres of white dwarfs, which are usually found inside rocky planets.
The surface gravity of white dwarfs is so intense that heavier elements will be attracted rather quickly, indicating that the star must have accreted material very recently, from a cosmic body that survived the star's death throes.
To try to determine how WD 1145 + 017 got the same thing, astronomers from the University of Colorado, Boulder, Weslin University and the University of Warwick in the UK ran a series of simulations to impose constraints on a space body destroyed by tidal gravity.
Simulations have shown that the bodies most likely producing what we see at WD 1145 + 017 have a small core and a low-density mantle 'resembling an asteroid with a partially differentiated structure and rich in volatile shells'.
'A multilateral approach will use the death of planetary systems in action to study fundamental properties of exoplanetary bodies that are otherwise unavailable: research in necroplanetology.'
The study was accepted by the Astrophysical Journal, and is available on arXiv.
Sources: Photo: NASA
