Little could Martí Perpinyà have imagined that his bachelor’s thesis would lead him to a scientific discovery of such importance in the field of astrophysics as the first resolved triple white dwarf system, named by scientists J1953-1019. The aim of his thesis at the UPC’s Barcelona School of Telecommunications Engineering (ETSETB) was to find white dwarf binary systems, which are also quite rare. Based on the second data release (DR2) collected by Gaia, one of the most important astronomical missions of the European Space Agency (ESA), Perpinyà found some 50 white dwarf binary systems, but also the triple system.

He confesses that at first he did not realise the importance of the finding: “When I first made the discovery, I was not aware of its impact. Two days later, after an email exchange between my supervisors and other collaborators, we realised that it was the first triple white dwarf system ever observed. At that moment, I felt very happy and very proud of my work. I would have never imagined that I would make such a discovery. It will mainly go unnoticed, but for me and for people in astrophysics it is very important, which is more than enough for me.”

An outstanding contribution to astrophysics
White dwarfs are the most common stellar remnants. When a star of less than 9 to 10 times the mass of the Sun exhausts the hydrogen it once used as a nuclear fuel, it becomes a white dwarf. Near the end of its nuclear burning stage, this type of star ejects most of its material into space, creating a nebula while its core contracts because of the force of gravity and it becomes denser. When the nebula is expelled, the remaining core, the white dwarf, will cool down over time. This is a phenomenon that will affect the majority of known stars, including the Sun.

Along with red dwarfs, white dwarfs are the most common stars in the Universe. They are about the size of Earth, yet their mass is comparable to that of the Sun, so they are extremely dense. Because of this, white dwarfs cannot exceed a certain mass limit (approximately 1.4 solar masses), beyond which they explode as a type Ia supernova (SNIa), one of the most luminous events in the Universe. An SNIa can be triggered, for instance, by the collision of white dwarfs in a resolved triple system. However, this configuration had never been observed until now. Measuring the stellar parameters of the three white dwarfs has proven that it is unlikely that the two inner white dwarfs collide, though if it occurs it could result in an SNIa.

As stated by Alberto Rebassa, professor at the UPC’s Department of Physics and cotutor of the thesis with professor Jordi José from the UPC and professor Boris T. Gänsicke from the University of Warwick, “the resolved triple white dwarf system helps demonstrate phenomena such as the stellar explosions explaining the accelerating expansion of the Universe.” Therefore, this finding “opens the door to scientific demonstrations of astrophysical theories that are currently on the table, with unimaginable repercussions in our knowledge of the Universe,” concludes the professor.

Recognition by the Royal Astronomical Society in London
The work of Martí Perpinyà has been recognized by the scientific community, and the digital magazine Monthly Notices of the Royal Astronomical Society has published the article ‘Discovery of the fist resolved triple white dwarf’, signed by Perpinyà, professor Alberto Rebassa and other scientists from European and American universities. In the paper, the researchers present the discovery of the three white dwarfs, describe their nature and analyse the future evolution of the system. The article was also published in volume 483 of the magazine’s printed version this February.

Monthly Notices of the Royal Astronomical Society is one of the world’s leading primary research journals in astronomy and astrophysics, as well as one of the longest established.