by Evan Jones (Swansea University)

In early 2018, the ESA Gaia spacecraft was busy observing the cosmos, detecting points of light in space as part of its mission to map out the physical features of our Galaxy. In Eastbury Community School, Barking, Essex, Megan Greet, the Head of Physics, was working on a project with her Year 13 students, which involved using the robotic Faulkes Telescopes to help identify exploding stars, or supernovae, in Gaia’s data. One object however stood out for the group – instead of showing the typical lightcurve of an exploded star, this object’s lightcurve looked different. Data was collected by pupil Jorgen Kolgjini, and collated by astronomer Dr Jaroslav Merc (Astronomical Institute of Charles University in Prague) to analyse. Further data was taken and the results discussed.

The outcome – Gaia18aen was not a supernova but a symbiotic star.

Merc explains further:
“Symbiotic stars are binary stars that typically consist of a cool evolved giant (usually of a spectral type K or M, meaning that they are cooler than the Sun) and a very hot and luminous white dwarf. The giant is losing mass in the form of a stellar wind. Part of it is accreted by the white dwarf. This interaction results in observable effects such as significant photometric brightenings (so-called outbursts) or changes in the spectroscopic appearance.”

Image 1 shows an artist’s illustration of a symbiotic binary system. Here you can see where the giant star is losing mass to the white dwarf forming an accretion disk and resulting in bipolar outbursts from the white dwarf.

Merc commented, “These objects are very interesting astrophysical laboratories. You can study the mass transfer, accretion of matter, stellar winds, jets, the formation of dust, and other astrophysical phenomena. Symbiotics are also important for the study of the evolution of binary stars.”

This was the very first discovery of a symbiotic star by the Gaia mission and proves that besides its mission to accurately measure the precise positions of stars in our Galaxy, Gaia can also be used to detect new types of interesting stars, and school pupils can help with these discoveries!

Merc also went on to comment on the relatively recent rapid increase of known symbiotic stars, which he has attributed to more specialist surveys of stellar objects, but also how this number of known symbiotic stars is still much lower than any estimate of the total population of symbiotic stars. He suggests that many of the symbiotic stars that we know about are often only discovered by “coincidence” as opposed to being sought out by space telescopes or probes like Gaia.

Fraser Lewis from the FT Project commented “We were delighted to be a part of this research, especially as it involved a teacher and her pupil contributing to an exciting astronomical discovery”.

It was this “coincidence” of Gaia18aen’s discovery by Jorgen Kolgjini and his teacher, Megan Greet that has led them to be included as authors on the published paper documenting the discovery of Gaia18aen – not bad for a day’s work in school!

For more information on the Gaia mission and how you can get involved visit https://www.gaia.ac.uk/ Or contact the Faulkes Telescope Project directly on info@faulkes-telescope.com