NASA Study Says Our Galaxy's Collision With Andromeda Has A 50/50 Chance
For decades, astronomers have said of our Milky Way galaxy is headed for an inevitable, head-on collision with its colossal neighbor, Andromeda, in approximately 4.5 billion years. This collision, often depicted as a spectacular, transformative event, has been a cornerstone of our understanding/presumption of galactic evolution. However, new research leveraging over a decade of data from the NASA/ESA Hubble Space Telescope, combined with observations from the Gaia space telescope, is challenging this long-held certainty.
The study, published this week on Nature, indicates that the likelihood of a direct collision between the Milky Way and Andromeda within the next 10 billion years is now a mere 50-50 chance. This significantly contrasts with previous studies that suggested such an encounter was almost guaranteed, potentially triggering a cascade of star formation and reshaping both galaxies into a new, grander form.
Astronomers in the study re-examined the precise motions of both galaxies, factoring in not only their approach but also their sideways movement. The initial measurements from Hubble a decade ago seemed to solidify the head-on collision scenario, as Andromeda's sideways motion appeared negligible. However, the latest, more comprehensive analysis, incorporating additional data and a more intricate understanding of galactic dynamics, has introduced greater uncertainty.
A crucial factor in this revised outlook is the gravitational influence of the Large Magellanic Cloud (LMC), a satellite galaxy of the Milky Way. Its presence and gravitational pull can subtly alter the Milky Way's trajectory, potentially veering it away from a direct impact with Andromeda. Researchers conducted 100,000 Monte Carlo simulations (spanning out to 10 billions years into the future), considering 22 different variables that could affect the potential collision. The sheer number of variables, each with its own inherent errors, contributes to a much larger uncertainty to the ultimate outcome.
Till Sawala, lead author and astronomer at the University of Helsinki in Finland noted that "it's somewhat ironic that, despite the addition of more precise Hubble data taken in recent years, we are now less certain about the outcome of a potential collision."
In roughly half of the simulations, the two colossal galaxies fly past each other, separated by around half a million light-years or less – about five times the Milky Way's diameter. That said, while they might move outward initially, they are still gravitationally bound and could eventually merge in the very distant future.
The study, published this week on Nature, indicates that the likelihood of a direct collision between the Milky Way and Andromeda within the next 10 billion years is now a mere 50-50 chance. This significantly contrasts with previous studies that suggested such an encounter was almost guaranteed, potentially triggering a cascade of star formation and reshaping both galaxies into a new, grander form.
Astronomers in the study re-examined the precise motions of both galaxies, factoring in not only their approach but also their sideways movement. The initial measurements from Hubble a decade ago seemed to solidify the head-on collision scenario, as Andromeda's sideways motion appeared negligible. However, the latest, more comprehensive analysis, incorporating additional data and a more intricate understanding of galactic dynamics, has introduced greater uncertainty.
A crucial factor in this revised outlook is the gravitational influence of the Large Magellanic Cloud (LMC), a satellite galaxy of the Milky Way. Its presence and gravitational pull can subtly alter the Milky Way's trajectory, potentially veering it away from a direct impact with Andromeda. Researchers conducted 100,000 Monte Carlo simulations (spanning out to 10 billions years into the future), considering 22 different variables that could affect the potential collision. The sheer number of variables, each with its own inherent errors, contributes to a much larger uncertainty to the ultimate outcome.
Till Sawala, lead author and astronomer at the University of Helsinki in Finland noted that "it's somewhat ironic that, despite the addition of more precise Hubble data taken in recent years, we are now less certain about the outcome of a potential collision."
In roughly half of the simulations, the two colossal galaxies fly past each other, separated by around half a million light-years or less – about five times the Milky Way's diameter. That said, while they might move outward initially, they are still gravitationally bound and could eventually merge in the very distant future.
