Milky Way’s violent birth decoded

• The Milky Way, home to our sun and billions of other stars, merged with another smaller galaxy in a colossal cosmic collision roughly 10 billion years ago, scientists said based on data from the Gaia space observatory.

What is Milky Way?

• The Milky Way is the galaxy that contains the Solar System, with the name describing the galaxy’s appearance from Earth.
• It resembles to a hazy band of light seen in the night sky formed from stars that cannot be individually distinguished by the naked eye.
• Galileo Galilei first resolved the band of light into individual stars with his telescope in 1610.

Its formation

• The union of the Milky Way and the so-called dwarf galaxy Gaia-Enceladus increased our galaxy’s mass by about a quarter and triggered a period of accelerated star formation lasting about 2 to 4 billion years.
• Galaxies of all types, including the Milky Way, began to form relatively soon after the Big Bang explosion that marked the beginning of the universe some 13.8 billion years ago.
• But they were generally smaller than those seen today and were forming stars at a rapid rate.
• Subsequent galactic mergers were instrumental in configuring galaxies existing now.

How was that verified?

• A high-precision measurement of the position, brightness and distance of around a million stars within 6,500 light years of the sun was obtained by the Gaia space telescope.
• It helped pinpoint stars present before the merger and those that formed afterward.
• Certain stars with higher content of elements other than hydrogen or helium arose in the Milky Way and others with lower such content originated in Gaia-Enceladus owing to its smaller mass.
• While the merger was dramatic and helped shape the Milky Way, it was not a star-destroying calamity.
• This crash was big in cosmic terms, but if it was happening now, we could probably not even notice at a human or solar system level.