What NASA calls "cosmic fossils" are evidence of terrifying behavior from the Milky Way's satellite galaxy.
NASA has just released a close-up photo of globular cluster NGC 2005, which the agency calls "a fossil of the universe".
The image was recorded by the Hubble Space Telescope, the most accomplished space explorer of NASA and its partner ESA (European Space Agency).
"Fossils of the universe" NGC 2005 - Photo: NASA
NGC 2005 itself is not an unusual globular cluster, but it becomes special when compared to its surroundings.
NGC 2005 is in a galaxy called the Large Magellanic Cloud (LMC), about 750 light-years from the center.
LMC is the largest satellite galaxy of the Milky Way, the galaxy containing our Earth.
Globular clusters are dense groups of stars that can contain tens of thousands or millions of stars, are tightly bound by gravity and are therefore very stable.
This stability contributes to their longevity: Globular clusters can be billions of years old and often include very old stars. So studying globular clusters in space could be like studying fossils on Earth.
Earth's fossils provide insight into the characteristics of ancient plants and animals, and globular clusters shed light on the characteristics of ancient stars.
Current theories of galaxy evolution predict that galaxies will merge with each other as they grow.
In particular, the Milky Way - a giant monster in the galactic world - once swallowed more than 20 other galaxies to achieve its current giant size.
The LMC satellite is much smaller than the Milky Way, but the globular cluster that Hubble just captured is evidence that it was also once a monster.
NGC 2005 is special compared to its surroundings because its stars have a different chemical composition than surrounding stars. This suggests that NGC 2005 did not originally belong to the LMC, but to an ancient galaxy that was swallowed by the LMC.
"The other galaxy merged long ago and dispersed, but NGC 2005 remained as an ancient witness to the merger," NASA wrote.
