Early galaxy may reveal answers about our own Milky Way
Researchers are looking to the stars to find out more about the origin story of our own galaxy.
Using data gathered by the ESO Very Large Telescope and the Hubble Space Telescope, researchers have been able to determine the size, mass, content of elements that make up another early galaxy and figured out how quickly it can form stars.
"Galaxies are deeply fascinating objects. The seeds of galaxies are quantum fluctuations in the very early universe and thus, understanding of galaxies links the largest scales in the universe with the smallest. It is only within galaxies that gas can become cold and dense enough to form stars and galaxies are therefore the cradles of star's births," co-lead researcher Johan Fynbo, professor at the Dark Cosmology Centre at the Niels Bohr Institute at the University of Copenhagen, said in a press release.
Back when the universe was forming, galaxies were created from large clouds of gas and dark matter. When gas cools down, it becomes so dense and compact that it collapses in on itself when gravity's pressure heats up its matter. That process creates a glowing ball of gas, or what we call a star.
Inside the stars, hydrogen and helium melt and form heavier elements carbon, nitrogen, oxygen. Eventually, magnesium, silicon and iron are formed. When the core of the star has turned to iron, no more energy can be taken out, and the star burns out and dies in a supernova explosion. This causes clouds of gas and other elements to be shot out into space, where new gas clouds form. The gas clouds cool and eventually become dense, the star process begins again.
Earlier stars only had 1/1000th of the amount of elements found in our own Sun. Today's galaxies have more stars and not as much gas compared to earlier galaxies. This means that newer stars contain even more elements, and heavier ones at that.
To figure out how the changes affect newer galaxies, researchers located a galaxy that started forming 11 billion years ago. In comparison, our galaxy, the Milky Way, is 13.2 billion years old.
"We want to understand this cosmic evolutionary history better by studying very early galaxies. We want to measure how large they are, what they weigh and how quickly stars and heavy elements are formed," co-lead researcher Johan Fynbo, a PhD student at the Dark Cosmology Centre at the Niels Bohr Institute, said.
The researchers followed a quasar, an active black hole that is brighter than a galaxy, to determine the location of the young galaxy. They were able to see the recently formed stars in the galaxy and figure out how many stars there were in relation to the total mass, which they calculated from stars and available gas.
This allowed them to figure out that heavier elements are equally spread throughout the younger galaxy, and that stars formed in the center of the galaxy help provide more gas for new stars in the outer regions.
The new stars also only contain about 1/3 as much oxygen as our Sun's original content. This means stars made at least 11 billion years ago and earlier may have enough elements to create livable habitats like the Earth.
The study was published on Tuesday in Monthly Notices of the Royal Astronomical Society.
