Even with a pair of binoculars you'd find it a hard task. The team has named that galaxy Enceladus, and the below video shows a simulation of its collision with the Milky Way. Stars from different galaxies have their own kind of fingerprint.
Some of these then became integrated into the Milky Way.
But thanks to the recent release of Gaia data - the most detailed and accurate map of the sky to date - a team of astronomers has been able to make much more detailed observations of the stars in the inner halo.
The research is described in a paper published today (Oct. 31) in the journal Nature.More news: Central government invoke section 7 Act, 1934: History and amendment
A newly discovered star is thought to be one of the oldest in the Milky Way. But in this scenario, Gaia wouldn't be down on the NY streets, squinting up 443 metres to the top of the tower.
The history of stars can be determined by their direction. They suspected that this could be the debris from a collision between the Milky Way and another galaxy ten billion years ago. This second galaxy would have been a smaller "satellite" companion of the Milky Way, travelling around it.
"It will give us unique insights on how galaxies looked like in the early universe and at high redshift, insights that are not possible to obtain by imaging those galaxies with Hubble, for example". That means that while this is hardly the only galactic collision scientists have pinpointed, it's a comparatively huge one, the scientists said.
The astronomers called this galaxy Gaia-Enceladus after one of the Giants in ancient Greek mythology, who was the offspring of Gaia, the Earth, and Uranus, the Sky.More news: Violence against NHS staff in England reaches five-year high
The team's modelling suggests that a collision with a satellite dwarf galaxy roughly the size of the Small Magellanic Cloud would have both populated the Milky Way's halo with stars, and heated the pre-existing thin disc, expanding it into a thicker one. However, ten billion years is a long time (even for astronomy) - long enough to scatter the debris from a merger all over the sky, rather than just in a clear stream. Compared to others, the stars that are scattered throughout are remarkably poor in heavier metals.
The team used spectroscopic observations from the APOGEE-2 survey - which measures the amounts of different elements in individual stars. For U.S. readers snacking their way through a Halloween haul, consider the injection of caramel that turns a simple 3 Musketeers bar into the cosmic candy we know and love called Milky Way. Exactly which element is formed depends on the star. Alpha elements - formed by combining multiple helium atoms - are created in explosions of massive, rapidly evolving stars, while iron is formed in supernovae from star systems where two stars orbit each other.
We know that the fraction of alpha elements in a galaxy decreases with time, while the fraction of iron increases.
The researchers found that the chemical signatures of many halo stars in the Milky Way were not the same as its "native" stars.More news: Sheriff's office places 'No Trick-or-Treat' signs at sex offenders' homes
"According to the legend, Enceladus was buried under Mount Etna, in Sicily, and responsible for local earthquakes". An outstanding question is whether a galaxy like the Milky Way is the product of many small mergers or of a few large ones. The stars now form most of our Galaxy's inner halo - a diffuse component of old stars that were born at early times and now surround the main bulk of the Milky Way known as the central bulge and disc. Like Enceladus the giant, Gaia-Enceladus was buried, hidden deep inside the galaxy. If Gaia could dig out the remains of this event that happened ten billion years ago, it is exciting to think what else it will uncover.