Cosmic grains of dust formed in supernova explosion

July 09, 2014

There are billions of stars and planets in the universe. A star is glowing sphere of gas, while planets like Earth are made up of solids. The planets are formed in dust clouds that swirled around a newly formed star. Dust grains are composed of elements like carbon, silicon, oxygen, iron, and magnesium. But where does the cosmic dust come from? New research from the Niels Bohr Institute at the University of Copenhagen and Aarhus University shows that not only can grains of dust form in gigantic supernova explosions, they can also survive the subsequent shockwaves they are exposed to. The results are published in the prestigious scientific journal, Nature.

How the cosmic dust is formed has long been a mystery to astronomers. The elements themselves are formed out of the glowing hydrogen gas in stars. The hydrogen atoms fuse together into heavier and heavier elements and in the fusion process the star emits radiation in the form of light, that is, energy. When all the hydrogen is exhausted and no more energy can be extracted, the star dies and giant clouds of gas are slung out into space, where they are recycled into new stars in a vast cosmic cycle.

The heavy elements are primarily formed in supernovae, which are massive stars that die in a gigantic explosion. But how do the elements grow into 'larger clumps' like cosmic dust grains?

The mystery of the origin of dust

"The problem has been that even though dust grains composed of heavy elements would form in supernovae, the supernova explosion is so violent that the grains of dust may not survive. But cosmic grains of significant size do exist, so the mystery has been how they are formed and have survived the subsequent shockwaves. Our research casts new light on this - both on how dust is formed and how it survives the shockwaves," explains Professor Hjorth, head of the Dark Cosmology Centre at the Niels Bohr Institute at the University of Copenhagen.

The researchers observe supernovae using the astronomical instrument X-shooter on the European Southern Observatory's Very Large Telescope in Chile. Part of the X-shooter was developed and built by Danish researchers at the Niels Bohr Institute and what is special about the instrument is both that it is extremely sensitive and the three spectrographs observe all light at once - from ultraviolet to visible light to infrared light. This is extremely important when observing phenomena in the distant universe.

Jens Hjorth explains that first they had to wait for the right, luminous supernova to explode. They were lucky and when it happened they initiated an observing campaign. This was a very bright supernova, 10 times brighter than the average supernova. The exploding star itself had been very massive, more than 40 times the mass of the Sun. Researchers from the Dark Cosmology Centre at the Niels Bohr Institute, Aarhus University, and NASA, among others, followed the explosion right from the start and the following 2½ years and analysed the light from the very bright supernova.

Dust formed through shock interaction

"Sust absorbs light and from our data we could calculate a curve that told us the about the amount of dust, the composition of the dust and the size of the dust grains. This showed something very exciting," explains Christa Gall, a postdoc at Aarhus University and affiliated with the Dark Cosmology Centre at the Niels Bohr Institute at the University of Copenhagen.

Christa Gall, who led the project, explains that the first step in dust formation is a mini-explosion, in which the star expels material containing hydrogen, helium and carbon. This gas cloud resides as a shell around the star. There are more of these outbursts and the shell around the star gets denser. Finally, the star explodes and the dense gas cloud take centre stage.

"When the star explodes, the shockwave hits the dense gas cloud like a brick wall. It is all in gas form and incredibly hot, but when the eruption hits the 'wall' the gas gets compressed and cools down to about 2,000 degrees. At this temperature and density elements can nucleate and form solid particles. We measured dust grains as large as around one micron (a thousandth of a millimeter), which is large for cosmic dust grains. They are so large that they can survive their onward journey out into the galaxy," explains Christa Gall.

The researchers believe they have thus found an avenue for how cosmic dust can form and survive the violent shockwaves of supernovae.
See film: X-shooter:

See film: Cosmic Explosions:

For more information contact:

Christa Gall, Postdoc at the Aarhus University and affiliated with the Dark Cosmology Centre at the Niels Bohr Institute at the University of Copenhagen.
+45 5366-2018, +

Jens Hjorth, Professor and head of the Dark Cosmology Centre at the Niels Bohr Institute at the University of Copenhagen. +45 3532-5928,

University of Copenhagen - Niels Bohr Institute

Related Supernova Articles from Brightsurf:

Scientists discover supernova that outshines all others
A supernova at least twice as bright and energetic, and likely much more massive than any yet recorded has been identified by an international team of astronomers, led by the University of Birmingham.

Supernova observation first of its kind using NASA satellite
Their research, detailed in the Monthly Notices of the Royal Astronomical Society, represents the first published findings about a supernova observed using TESS, and add new insights to long-held theories about the elements left behind after a white dwarf star explodes into a supernova.

Astronomers find possible elusive star behind supernova
Astronomers may have finally found a doomed star that seemed to have avoided detection before its explosive death.

Stellar thief is the surviving companion to a supernova
Hubble found the most compelling evidence that some supernovas originate in double-star systems.

Supernova may have 'burped' before exploding
Only by increasing the rate at which telescopes monitor the sky has it been possible to catch more Fast-Evolving Luminous Transients (FELTs) and begin to understand them.

An unusual white dwarf may be a supernova leftover
Astronomers have identified a white dwarf star in our galaxy that may be the leftover remains of a recently discovered type of supernova.

Researchers show how to make your own supernova
Researchers from the University of Oxford are using the largest, most intense lasers on the planet, to for the first time, show the general public how to recreate the effects of supernovae, in a laboratory.

The big star that couldn't become a supernova
For the first time in history, astronomers have been able to watch as a dying star was reborn as a black hole.

Seeing quadruple: Four images of the same supernova, a rare find
Galaxies bend light through an effect called gravitational lensing that helps astronomers peer deeper into the cosmos.

Explosive material: The making of a supernova
Pre-supernova stars may show signs of instability for months before the big explosion

Read More: Supernova News and Supernova Current Events is a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for sites to earn advertising fees by advertising and linking to