University of Warwick astronomers have uncovered the chemical fingerprint of a frozen, water-rich planetary fragment being consumed by a white dwarf star outside our Solar System.
In our Solar System, it is thought that comets and icy planetesimals (small solid objects in space) were responsible for delivering water to Earth. The existence of these icy objects is a requirement for the development of life on other worlds, but it is incredibly difficult to identify them outside our Solar System as icy objects are small, faint and require chemical
In a study published in MNRAS, astronomers from Warwick, Europe and the US have found strong evidence that icy, volatile-rich bodies – capable of delivering water and the ingredients for life – exist in planetary systems beyond our own.
To make this discovery, the group used ultraviolet spectroscopy from the Hubble Space Telescope to study the chemical make-up of distant stars. One star, WD 1647+375, stood out as having ‘volatiles’ (chemical substances with low melting points) on the surface. White dwarf atmosphere is typically made up of hydrogen and helium, but WD 1647+375 had elements such as carbon, nitrogen, sulphur and oxygen.
This volatile-rich atmosphere was the first clue that WD 1647+375 was different.
Lead author Snehalata Sahu, Research Fellow, Department of Physics, University of Warwick said: “It is not unusual for white dwarfs to show signatures of calcium, iron and other metal from the material they are accreting (absorbing). This material comes from planets and asteroids that come too close to the star and are shredded and accreted. Analysing the chemical make-up of this material gives us a window into how planetesimals outside the Solar System are composed.
“In this way, white dwarfs act like cosmic crime scenes — when a planetesimal falls in, its elements leave chemical fingerprints in the star’s atmosphere, letting us reconstruct the identity of the ‘victim’. Typically, we see evidence of rocky material being accreted, such as calcium and other metals, but finding volatile-rich debris has been confirmed in only a handful of cases.”
