If you look closely at the haze of gas and starlight that is our galaxy, you’ll find traces of a violent history. However, the scars of our past are not always easy to distinguish from the more mundane waves that advance cosmic evolution, leading researchers to speculate which patterns are evidence of cataclysmic events and which are typical signs of aging.
Using data collected by the Gaia satellite, an international team of researchers has uncovered what could be details of a hypothetical dust between the Milky Way and an orbiting star body.
Since the 1960s, a series of studies have slowly revealed a distinct “S”-shaped curvature that can be seen in the disc of our galaxy, which is speculated to be the product of repeated collisions with a smaller neighbor, such as would be the Dwarf Galaxy in Sagittarius.
According to a recent analysis, the positions and motions of tens of thousands of stars spanning a quarter of our galaxy suggest that the kink may itself be the quiet sound of a wave propagating through large-scale deformation.
A hypothetical dust between the Milky Way and an orbital body of stars
Led by astronomer Eloisa Poggio of the Italian National Institute of Astrophysics, the team compared data on about 16,000 young giants and about 3,400 “distance marker” stars known as Cepheids, statistically correlating their forward and backward motions with their up and down.
The result is an oscillation eerily similar to the rolling motion of ocean waves traversing the star masses at the center of the Milky Way above, but distinct from the tsunami erupting below, he writes ScienceAlert.
While the ripple barely rises above the plane of the galaxy, its spatial extent is vast, calculated to extend more than a quarter of the way to the edges of the disc, with stars moving outwards deviating from their trajectories by about 10 to 15 kilometers per second.
It is debatable whether the radial and vertical motions are connected, or whether the undulation and core deformation should have a common cause.
Cataclysmic events or typical signs of aging?
Just by removing the signature of the curvature of the Milky Way itself, the remaining variations in the positions of the stars suggested that there might even be some kind of anomaly.
“The warp and the wave don’t necessarily have to be caused by the same event,” Poggio explained to ScienceAlert. “However, we will try to explore this point in the future using numerical simulations.”
Our galaxy hides its “bruises” well. Only by looking for the subtle signatures of stars sitting out of place or moving in a curious direction might we find a reason to look for traces of the past.
“Future work looking at other data sets, as well as different galaxy formation models, will reveal further details of the formation and evolution of the observed feature, as well as a more detailed dynamical description of how waves propagate in the Milky Way’s disc,” the researchers conclude in their report.
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Source: www.descopera.ro
