The Hubble Space Telescope has done it again, capturing an incredibly detailed, macabre view of a dramatic galactic merger. This particular cosmic battle is set to be a pretty one-sided affair, as the majestic barred spiral galaxy NGC 1512 bears down on its victim – the (relatively) puny dwarf galaxy NGC 1510.
NGC 1512 spans roughly 70,000 light-years from end to end, making it comparable in size to our own Milky Way galaxy. Therefore, you could be forgiven for thinking that the little dwarf NGC 1510 would have little effect on its monstrous partner.
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The merger of the two galaxies represents a vital element of galactic evolution. Even prior to the inevitable collision, the pair are actively helping one another to mature by kick-starting dramatic bursts of star formation.
It is likely that the bar running horizontally through NGC 1512 formed at least in part as a result of the gravitational influence of NGC 1510. This bar is funneling raw material toward the heart of the galaxy, where it has prompted an explosion of star formation in the 2,400 light-year wide region encircling the center of the galaxy, known as the circumnuclear starburst ring.
Composite Hubble image of the barred spiral galaxy NGC 1512 (left) and the dwarf galaxy NGC 1510 (right). Both galaxies are located roughly 30 million light-years away in the constellation of Horologium (Credit: ESA/Hubble, NASA)
The feature can be easily spotted as a bright blue ring, which is shining with the light of countless star clusters comprised of hot, young stellar bodies. Subtler evidence of star formation can also be seen marking the outer disk of NGC 1512.
At dozens of points throughout the outer disk of the galaxy, we see knots of light representing the emission glow from enormous clouds of hydrogen gas. This glow is created as ultraviolet light emitted by hot young stars embedded within the clouds ionizes the hydrogen gas, causing it to give off its own light.
As NGC 1510 draws ever nearer to its end, the powerful gravitational influence of its neighboring partner has stirred up the dwarf's star-creating materials, giving rise to intense levels of star formation that have caused the galaxy to glow a fierce blue.
Artists impression of the Andromeda galaxy and the Milky Way closer to the point of the merger (Credit: NASA; ESA; Z. Levay and R. van der Marel, STScI; T. Hallas; and A. Mellinger)
The merger, which has already been going on for 400 million years, will inevitably conclude with the dwarf galaxy being absorbed into NGC 1512. As it turns out, NGC 1510 is not the only victim of this celestial fiend. In 2015, it came to light that NGC 1512 has a history when it comes to galactic cannibalism, as it was revealed that the outer regions of its spiral arms are actually formed from a separate, even older galaxy.
Still, before we judge NGC 1512 too harshly for its murderous ways, we must remember that the Milky Way is itself composed of numerous smaller galaxies that have wandered across its path in the distant past, and will itself merge with the neighboring Andromeda galaxy in about four billion years.
Don't worry though, our solar system is likely to survive the collision, which computer simulations suggest will result in the birth of a single, enormous elliptical galaxy. The downside is that, if human beings somehow survive long enough to see the creation of this new monster, they will be living in a galaxy that some astronomers are already starting to refer to as Milkomeda.
I for one wouldn't want to live in a galaxy that sounds like a poorly branded dairy drink.
Source: Hubble Space TelescopeView gallery - 4 images