It’s been 32 years since NASA launched Hubble Space Telescope into orbit. And just like every year, the anniversary is marked by a photo that Hubble captured on duty.
To celebrate Hubble’s 32nd birthday, NASA has shared yet another remarkable image. It shows an unusual close-knit collection of five galaxies, called The Hickson Compact Group 40.
“Though such cozy galaxy groupings can be found in the heart of huge galaxy clusters, these galaxies are notably isolated in their own small patch of the universe, in the direction of the constellation Hydra.
One possible explanation is that there’s a lot of dark matter (an unknown and invisible form of matter) associated with these galaxies. If they come close together, then the dark matter can form a big cloud within which the galaxies are orbiting. As the galaxies plow through the dark matter they feel a resistive force due to its gravitational effects. This slows their motion and makes the galaxies lose energy, so they fall together.
Therefore, this snapshot catches the galaxies at a very special moment in their lifetimes. In about 1 billion years they will eventually collide and merge to form a giant elliptical galaxy.”
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