It can resolve uncertainties in distances to critical stars called Cepheids - like Polaris, the North Star - that are the bottom rung of the distance ladder, where each rung is a single step, but by the time you get to the top you’re measuring distances on a cosmic scale.Īnd in this new case, it reveals the remnants of a long-dead galaxy, one used as sustenance for our own.Īrtwork depicting the stars from Gaia-Enceladus (arrows indicate their velocity) merging with the Milky Way based on actual physical simulations. In others it can reveal hidden denizens of the Milky Way. How can mapping stars be so important? In some cases it can solve long-standing puzzles that have irritated astronomers for decades. Gaia has provided nothing short of a revolution in astronomy.
It is in the process of mapping the positions, motions, colors, and most importantly the distances of well over a billion stars.
The stars in question were mapped by Gaia, a European Space Agency satellite. And that time was a staggering ten billion years ago. By mapping huge numbers of stars in the galaxy, astronomers have found compelling evidence that the Milky Way ate a galaxy that was, at the time, about a quarter its size.
These are usually relatively recent events involving a much smaller galaxy.īut a new result changes that. For another, we can track stars on our galaxy that were once part of another galaxy, but were absorbed into our own. For one, we can see other galaxies colliding and merging all over the sky. Our Milky Way galaxy grows by eating other galaxies.
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