ast radio bursts have a characteristic sweeping signal, shown in the final inset 'waterfall plot'. Pinpointing a fast radio burst's source requires a multi-telescope approach to zoom in – in this case, to an elliptical galaxy.
CREDIT: DAVID KAPLAN AND EVAN KEANE
What seems to be a simple game of "hide and seek" has huge implications for astronomers. Only 16 fast radio bursts have been detected, and their source is a cosmological mystery.
This particular fast radio burst appeared to come from a massive “trainwreck” galaxy six billion light-years away, which formed 100 billion Suns’ worth of stars, but is currently almost dead.
At the moment it's producing less than two Suns a decade (a factor of ten less than our much-smaller Milky Way galaxy).
Without new stars, the source of fast radio bursts seems to be collisions of dense, long-dead stars known as neutron stars, which typically explode as short gamma ray bursts.
There may even be different classes of objects that produced the 16 currently known fast radio bursts.
.
ast radio bursts have a characteristic sweeping signal, shown in the final inset 'waterfall plot'. Pinpointing a fast radio burst's source requires a multi-telescope approach to zoom in – in this case, to an elliptical galaxy.
CREDIT: DAVID KAPLAN AND EVAN KEANE
What seems to be a simple game of "hide and seek" has huge implications for astronomers. Only 16 fast radio bursts have been detected, and their source is a cosmological mystery.
This particular fast radio burst appeared to come from a massive “trainwreck” galaxy six billion light-years away, which formed 100 billion Suns’ worth of stars, but is currently almost dead.
At the moment it's producing less than two Suns a decade (a factor of ten less than our much-smaller Milky Way galaxy).
Without new stars, the source of fast radio bursts seems to be collisions of dense, long-dead stars known as neutron stars, which typically explode as short gamma ray bursts.
There may even be different classes of objects that produced the 16 currently known fast radio bursts.
.
An elliptical galaxy showing its fast radio burst pulse detected at Parkes.
CREDIT: DAVID KAPLAN AND DAWN ERB
But even though the cause of this fast radio burst is still a mystery, its light can be used to illuminate the otherwise impossible-to-detect wisps of material that lies between the galaxies in what’s called the “intergalactic medium”.
It’s hard to picture just how empty this space is – barely a handful of atoms per cubic metre. The same volume of air you’re breathing now contains a trillion trillion atoms.
If space was truly empty, radio waves from the explosion would race outwards at the speed of light. But even these few atoms will cause a noticeable delay over billions of light-years.
In particular, they slow down lower frequencies of light, This is a little like how white light shining through a glass prism splits into a rainbow as the redder colours (with lower frequencies) travel slower than blue.
This delay has a precise relation with distance. And with the six-billion-light-year distance to the host galaxy now known, astronomers calculated the average density of the material along our line of sight, and directly weighed the atomic content of the Universe.
The intergalactic medium, together with all atoms in stars, planets and gas in galaxies, makes up just 5% of the contents of the Universe. The rest is an unknown particle holding galaxies together termed Dark Matter, and an even more mysterious Dark Energy driving galaxies apart.
The 5% value is in perfect agreement with measurements made from the afterglow of the Big Bang, the Cosmic Microwave Background.
We are a small component of the Universe, but as far as we know, the only piece to look back and measure itself.
So don’t feel small – feel unique!
Quelle: COSMOS
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