The Milky Way May Be Swarming With Planets That Have Continents and Oceans Like Earth
https://scitechdaily.com/the-milky-...new study,particles containing ice and carbon.
"“All planets in the Milky Way may be formed by the same building blocks, meaning that planets with the same amount of water and carbon as Earth,” says Professor Anders Johansen. Credit: NASA, ESA and G. Bacon (STScI)
Using a computer model, Anders Johansen and his team have calculated how quickly planets are formed, and from which building blocks. The study indicates that it was millimetre-sized dust particles of ice and carbon – which are known to orbit around all young stars in the Milky Way – that 4.5 billion years ago accreted in the formation of what would later become Earth.
“Up to the point where Earth had grown to one percent of its current mass, our planet grew by capturing masses of pebbles filled with ice and carbon. Earth then grew faster and faster until, after five million years, it became as large as we know it today.
Along the way, the temperature on the surface rose sharply, causing the ice in the pebbles to evaporate on the way down to the surface so that, today, only 0.1 percent of the planet is made up of water, even though 70 percent of Earth’s surface is covered by water,” says Anders Johansen, who together with his research team in Lund ten years ago put forward the theory that the new study now confirms.
The theory, called “pebble accretion,” is that planets are formed by pebbles that are clumping together, and that the planets then grow larger and larger.
Anders Johansen explains that the water molecule H2O is found everywhere in our galaxy, and that the theory therefore opens up the possibility that other planets may have been formed in the same way as Earth, Mars, and Venus.
“All planets in the Milky Way may be formed by the same building blocks, meaning that planets with the same amount of water and carbon as Earth – and thus potential places where life may be present – occur frequently around other stars in our galaxy, provided the temperature is right,” he says."
