The two ice giants created a blaze of light.
A chance social media post by an eagle-eyed amateur astronomer sparked the discovery of an explosive collision between two massive planets.
The two ice giant exoplanets collided around a sun-like star, creating a blaze of light and plumes of dust in a distant space system 1,800 light-years away from Earth.
An international team of astronomers was formed after an enthusiast viewed the light curve of the star and noticed something strange.
It showed the system doubled in brightness at infrared wavelengths some three years before the star started to fade as the result dust cloud blocked its light.
‘To be honest, this observation was a complete surprise to me,’ said co-lead author Dr Matthew Kenworthy, from Leiden University, the Netherlands.
‘When we originally shared the visible light curve of this star with other astronomers, we started watching it with a network of other telescopes.
‘An astronomer on social media pointed out that the star brightened up in the infrared over a thousand days before the optical fading. I knew then this was an unusual event.’
The network of professional and amateur astronomers studied the star intensively, including monitoring changes in its brightness over the next two years.
The star was named ASASSN-21qj after the network of telescopes that first detected the fading of the star at visible wavelengths.
The researchers concluded the most likely explanation is that two ice giant exoplanets collided, producing the infrared glow detected by Nasa’s Neowise mission, which uses a space telescope to hunt for asteroids and comets.
‘Our calculations and computer models indicate the temperature and size of the glowing material, as well as the amount of time the glow has lasted, is consistent with the collision of two ice giant exoplanets,’ said co-lead author Dr Simon Lock, from the University of Bristol.
The resultant expanding debris cloud from the impact then travelled in front of the star some three years later, causing the star to dim in brightness at visible wavelengths.
Over the next few years, the cloud of dust is expected to start smearing out along the orbit of the collision remnant, and a tell-tale scattering of light from this cloud could be detected with both ground-based telescopes and Nasa’s largest telescope in space, known as JWST.
The astronomers plan on watching closely what happens next in this system.
‘It will be fascinating to observe further developments,’ said co-author Dr Zoe Leinhardt, from the University of Bristol. ‘Ultimately, the mass of material around the remnant may condense to form a retinue of moons that will orbit around this new planet.’
The study is published in the journal Nature.
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