James Webb discovers silicate and carbonate particles in the disk of a dirty white dwarf

Bodies destroyed by dwarves can be quite large. The James Webb Infrared Space Telescope has discovered traces of silicate and carbonate minerals in the disk around contaminated white dwarf WD 0145+234. This may indicate that the objects previously destroyed by the dwarves were quite large objects within which reactions involving liquid water had occurred. The preprint is available at arXiv.org. White dwarfs appear at the end of the life cycle of low- and medium-mass stars;

Our Sun will also transform into one after its red giant phase. High surface gravity causes heavy elements to sink below the photosphere of white dwarfs, leaving their atmospheres mostly hydrogen or helium. However, many dwarves are known to have atmospheres contaminated with traces of heavy elements, which has been linked to the accretion onto dwarves of bodies destroyed by tidal forces from the disk around them. . This gives scientists an unusual way to study material from main sequence star systems left behind by planets, dwarf planets, asteroids or planetesimals.

A team of astronomers led by Andrew Swan from the University of Warwick has presented the first spectroscopic observation of a contaminated white dwarf by the James Webb Telescope. Observations were made with the MIRI and NIRSpec infrared instruments, the first on July 26, 2022, and the following five observations at intervals of 3, 6, 12, 21 and 357 days . The study’s target was WD 0145+234, a bright white dwarf that produced an infrared flare in 2018 (which has since diminished), possibly the result of a large object falling into the dwarf. The dwarf itself has a temperature of 13,000 kelvin and a mass of about 0.67 solar masses, is contaminated with heavy elements, and is surrounded by a disk of emitting gas. The dwarf is located 95.8 light years from the Sun.

Observations show that the circumstellar disk returns to a quiet state, revealing excess infrared radiation similar to that of typical dusty white dwarfs. The researchers noticed the presence of fine silicate dust whose particles can continuously collide with each other. It is thought that these are most likely enstatite grains, but may also be forsterite. There is also evidence of carbonate minerals in the dust; If this is further confirmed, then we can say that the objects destroyed by the dwarves were large enough (tens of kilometers) for chemical reactions involving liquid water to occur inside them.

Source: https://arxiv.org/pdf/2310.09355.pdf