The death throes of massive stars that have gone supernova are the answer to the long-standing puzzle of what supplied our early universe with dust, according to a new study.
The origin of the dust that exists in the interstellar medium is very important as it plays a crucial role in the formation of stars and plates. Its heavy atoms like carbon, silicon, oxygen and iron were not produced in the Big Bang and must have formed later.
Galaxies including our Milky Way contain not only countless stars, but also large masses of gas and cosmic dust, indispensable to star formation.
Although they are only a minor part of the Universe and our Solar System, they are the main constituents of rocky planets like Earth and thus of life itself: many of the atoms we are made of were once part of the dust in the Universe.
However, it is not fully understood where this dust comes from, especially in the distant and thus young Universe, but now we have an indication.
The many old red giant stars in today’s Universe are thought to be the major dust producers, with the grains condensing like soot in a chimney as warm gases flow away from the star.
In a study published online July 7 in Science magazine, with the help of European Space Agency's Herschel telescope, a team of 22 researchers, including Dr Mikako Matsuura from the University College London, found that Supernova 1987A ejected a huge amount of cold grains of dust into space, an amount equivalent to 40 to 70 percent the mass of the sun.
Interestingly, this brand new clue does not come from observation of very distant galaxies, but from one of our closest galactic neighbours, said Mikako Matsuura, who lead the study published in the journal Science.
With SN1987A, we can investigate details that are almost impossible to discern in supernovae inside more distant galaxies. This helps us improve our understanding of these stellar explosions, which we can then apply to the broader context of galaxy evolution, added Matsuura.
This is a star 160,000 light years away, and even though we first saw it on Feb 23, 1987, the star blew up 160,000 years ago, and it took that long for the light to get to us, said LSU Astrophysics Prof. Geoffrey Clayton.
Supernovae are what happen to massive stars towards the end of their lives. Stars shine via nuclear fusion, turning hydrogen into helium, and then helium into carbon and heavier elements. Eventually, the star starts making iron. When that happens, the amount of energy released from fusing into anything heavier is less than what it takes to fuse the atoms. So the iron falls as ash to the center of the star.
When the iron core reaches a certain size, the star can't generate enough energy to support the outer layers (which are made up of hydrogen, helium and other heavier elements). The star collapses in a few seconds, and the mass of material bounces off the core, with so much energy that the star van shine more brightly than the galaxy it is in. What's left is a neutron star, a ball of neutrons a few miles across and so dense that a cubic centimeter weighs a metric ton.