TESS Finds a Triple Star System that Could Fit within Mercury’s Orbit

TESS, the Transiting Exoplanet Survey Satellite has been on the lookout for alien worlds since 2018. It has just hit the news again having identified an extreme triple star system where two stars orbit each other every 1.8 days. The third component circles them both in 25 days – this puts the entire system within the orbit of Mercury with a little wriggle room to spare! To visual observers, it looks like a single star but the power of TESS revealed a flicker as the stars line up and pass one another along our line of sight. Eventually, the two inner stars will merge, triggering a supernova event!

Exoplanets are planets in orbit around other star systems. Unlike the familiar planets in our own Solar System, their size and composition varies widely. To date gas giants larger than Jupiter have been found and small rocky worlds similar to Earth have been spotted. The techniques to hunt down the alien worlds vary from the transit method to the radial velocity method which detects a star’s wobble caused by the presence of a planet. Using these various different techniques, over 5,000 exoplanets have been identified.

TESS was launched by NASA in April 2018 with the purpose of hunting down exoplanets. It uses the technique that relies upon searching for transit events as planets cross the face of their host star. Since it began operations, TESS has monitored the brightness of over 200,000 stars looking for tiny dips in brightness. It’s been particularly focussed on looking for Earth sized planets orbiting within a stars habitable zone. Here the conditions are such that a planet could support liquid water and therefore may harbour life. 

In an exciting twist to the usual approach for hunting exoplanets, a team of professional and amateur astronomers have joined forces with artificial intelligence and found a strange new multiple star system. Called TIC 290061484 it consists of twin stars orbiting each other every 1.8 days and a third star that orbits them both in just 25 days.  The discovery beats the existing record for the shortest outer orbital period of a stellar system that was set in 1956 by 8 days! 

The edge-on presentation of the system is perfectly aligned for analysis. Monitoring the movement and brightness changes it is possible to measure orbits, masses, sizes and temperatures of the stellar components. The team, led by Veselin Kostov from NASA’s Goddard Space Flight Center published their findings in the Astrophysical Journal. 

Using TESS’ sensitivity to pickup flickering and brightness changes, the nature of the triple star system was revealed. Located in the constellation Cygnus almost 5,000 light years away the team monitored the dips in brightness as one star passed in front of the other. Using the capability of AI and machine learning, the team were able to filter the immense amounts of data to identify dimming events from transits rather than just the flicking of light caused by our own atmosphere. 

The data was then analysed by teams of citizen scientists who had formed ‘The Planet Hunters’ in 2010 to support exoplanet surveys. They later joined forces with professional astronomers as ‘the Visual Survey Group’ where they would provide real visual assessment of survey results. The team have now developed the model for the system and even forecast that, in between 20 to40 million years, the inner stars will expand and trigger a supernova explosion. 

The hunt is now on for more close multiple star systems with the Nancy Grace Roman Space Telescope (NGRST) joining the hunt. With its far higher resolution, NGRST will offer 36,000 pixels where TESS only offered 1, giving a new window on the same region of the Galaxy.

Source : NASA’s TESS Spots Record-Breaking Stellar Triplets