This may look like a regular galaxy, but all isn’t as it seems (Picture: Nasa/ESA/CSA/Webb/L Armus/A Evans)
The James Webb Space Telescope (JWST) has given astronomers another insight into the universe’s history – this time the aftermath of a cosmic collision between two galaxies half a billion years ago.
An image taken by the telescope shows NGC 3256 as a glowing swirl of red and orange punctuated by brilliant shining stars, 120 million light-years away in the Hydra-Centaurus Supercluster. However, something in the mass of stars and dust gives away its past, and the fact it was once one not one galaxy, but two.
As galaxies collide, they channel together the gas and dust needed to form new stars. This can be seen in the brighter regions of NGC 3256, where young stars blast out infrared light which irradiates small grains of dust, giving the galaxy its distinctive glow picked up by the JWST.
‘The galactic collision that created NGC 3256 triggered a luminous burst of star formation that can be seen in the brightest portions of this Webb image,’ said the James Webb team.
‘These infant stars shine most brightly at infrared wavelengths, light which can penetrate through obscuring dust in the galaxy, and which makes the stars perfect subjects for Webb.’
However, older stars are normally safe when galaxies collide, thanks to the large distances between them – our closest star after the Sun is Proxima Centauri, about 25 trillion miles away.
‘If you were asked to picture a galaxy collision, you might picture stars careening into one another with catastrophically explosive results,’ said the team. ‘In reality, the spaces between the stars in a galaxy are vast – when galaxies collide, their clouds of stars pass through one another and mingle like two clouds of smoke.’
In the case of NGC 3256 however, there were some stellar casualties, seen as the long red tendrils of stars pulled out of their original galaxies by the immense gravitational forces of the collision. These are called ‘tidal features’.
‘The tumultuous past of NGC 3256 is captured in the long tendrils of shining dust and stars which extend outwards from the main body of the galaxy,’ added the team.
The study of NGC 3256 and other colliding galaxies can teach astronomers more about the formation of our own galaxy. As they merge, so too do their black holes.
Last week scientists discovered that as black holes circle each other before colliding, they produce low-frequency gravitational waves that reverberate across the galaxy, changing space-time as they travel.
In January, the JWST spotted its first alien planet. Its first images, revealed last July, showed the universe 13 billion years ago.