NASA's venerated Hubble Space Telescope has captured a striking image of the larger galaxy NGC 7714 colliding with its smaller companion NGC 7715. A similar cataclysmic collision is due to take place between our own galaxy – the Milky Way – and our closest neighbor, the Andromeda galaxy, in around four billion years. The image itself is a composite, comprised of a number of images captured by Hubble over a wide range of wavelengths.
NGC 7715 is categorized as a Wolf-Rayet starburst galaxy due to the large, extremely hot and relatively short-lived stars that make up the celestial giant. Somewhere between 100 to 200 million years ago, NGC 7715 drifted too close to its galactic neighbor NGC 1174, triggering a dramatic change in the galaxy's structure.
NASA graphic showing Andromeda featuring prominently in the night sky, as it will in 3.75 billion years (Image: NASA; ESA; Z. Levay and R. van der Marel, STScI; T. Hallas; and A. Mellinger)
As the two galaxies approached each other, the colossal forces emanating from the wandering giants tortured and disrupted each other's structures, leaving us with the irregularly-shaped galaxies we have today. The larger galaxy has had two long tails of stars ripped away, flinging vast amounts of material out into the space between the giants.
This in turn has formed a sort of galactic bridge, funneling materials from the smaller galaxy and feeding a bright burst of star formation in NGC 7714. The formation is predominantly taking place in the galactic center of NGC 7714, however the process is evident throughout the entire galaxy to a lesser extent.
It is a comforting thought that, in four billion years when we collide with our closest neighbor Andromeda, we may find ourselves ushering in a fresh explosion of star formation in the now-distant galaxy.