New Gaia Observations Reveal The Galaxy Is Formed ‘Inside-Out’


A new breakthrough using data from the Gaia-ESO project provides new insight into our Milky Way galaxy. It supports the fact that the galaxy might have formed the inside-out with the inner region forming faster than the outer reaches.

The European Space Agency’s Gaia satellite has been launched this month. It has provided substantiation supporting up theoretically-predicted divisions in the chemical composition of the stars that make up the Milky Way’s disc – the vast collection of giant gas clouds and billions of stars that give our Galaxy its ‘flying saucer’ shape.

The Gaia-ESO survey, the Earth-based component of the survey mission, includes the European Southern Observatory’s Very Large Telescope, VLT, in Chile.

Astronomers tracked fast-produced elements like magnesium to see how quickly different parts of the Milky Way were formed.

“The different chemical elements of which stars – and we – are made are created at different rates – some in massive stars which live fast and die young, and others in sun-like stars with more sedate multibillion year lifetimes,” said Professor Gerry Gilmore, a Cambridge University professor of astronomy, lead investigator on the Gaia-ESO Project.

The images snapped in the project also provide new insight on the much-pondered “double structure” of the Milky Way’s disc – the idea that there might be “thin” and “thick” discs.

Metallicity is the concentrations of chemicals other than hydrogen and helium. The two fundamental ingredients of stars are hydrogen and helium.


During the latest research, the team found that the stars in the young, ‘thin’ disc aged between 0 – 8 billion years all have a similar degree of metallicity, regardless of age in that range, with many of them considered ‘metal-rich’.

There is a “steep decline” in metallicity for stars aged over 9 billion years, typical of the ‘thick’ disc, with no detectable ‘metal-rich’ stars found at all over this age.

But stars of different ages and metallicity can be found in both discs.

Massive stars also have the tendency to lead a short life with a violent end. The violent end produces huge amounts of magnesium while going supernova. The deaths of such stars can also form a neutron star or in some cases black hole.

“We have been able to shed new light on the timescale of chemical enrichment across the Milky Way disc, showing that outer regions of the disc take a much longer time to form,” said study leader Maria Bergemann from Cambridge’s Institute of Astronomy. “This supports theoretical models for the formation of disc galaxies in the context of Cold Dark Matter cosmology, which predict that galaxy discs grow inside-out.”

The findings titled “The Gaia-ESO Survey: radial metallicity gradients and age-metallicity relation of stars in the Milky Way disk” was published in the journal Astronomy and Astrophysics.

  • Ulises

    Along with this cosmic evolution, which is the probability that within the milky way, from the dust of its exploded stars, the living being who uses a computer was formed – computer included? A favourable case among infinite unfavourable possibilities? Fifty-fifty? To be or not to be, is that the question? Or is it a zero followed by a radix point and an infinite amount of zeros behind, but finishing with a one emerging from error or compassion when rounding up? Are calculations simplified or made more complex when the subjective self of each one is the entity that is studied? Anyway , what is the relationship between life and immense numbers? Is life a folding process of infinity? Is it just something infinite that would have enough to allow a self, something of infinite claims? But, is infinity credible within something with a beginning, out of a Big Bang? And is it credible within something with an ending, with the inevitable death around the corner? Along these lines, there is a peculiar book, a preview in Just another mind leisure suggestion, in order to freethink for a while

    • Martel

      There are at least one million planets in our little galaxy with carbon based life on them. A significant portion of those planets have had, will have, or currently have intelligent life. The most pertinent question would be how long a very intelligent tool using species persists before it annihilates itself. That may only be a short time, in other words a high order of intelligence may choose to conflict directly with the very social traits which enabled the intelligence to develop. If that’s the case we may never be able to find another intelligent species living around another star with whom we could communicate, as we would not be able to carry out such communication until another intelligent species develops sufficiently on another planet so as to communicate with us…and we would be extinct by that time.

  • Tyler Brown

    Since black holes are at the center of the galaxy, does that mean they come first?

  • Alfonso Bergamo

    No one has a clue of the universe or our existence.
    It s okay to know you don t know

    • Pluto Animus

      People like Alfonso, who choose to remain ignorant of the discoveries of science, have no clue.

      The rest of us can exult in the knowledge science brings us every day.

      • Alfonso Bergamo

        You re in denial, we don t have a clue

        • Matthew Kirwan

          Don’t project your personal failings upon the rest of the population. Just because you’re an ignorant moron, doesn’t mean that we all are.

  • adarsha rao

    > But stars of different ages and metallicity can be found in both discs.
    > This supports …. that galaxy discs grow inside-out

    Aren’t these two statements contradictory? If galaxy formed inside out there should have been metal-rich new stars only in thin disk.