Catch a fallen star. The Cassini spacecraft orbiting Saturn has picked up three dozen specks of stardust from interstellar space, a find that will help astronomers understand how bits of exploded stars wend their way through the cosmos and are reborn in new star systems.
Though mostly cold and empty, interstellar space contains wisps of gas and fine particles of dust that were released in the fiery deaths of giant stars. Similar in size and composition to grains of sand, the dust particles are a record of the heavy elements that determine the chemical makeup of new stars and galaxies.
鈥淭hey are of fundamental importance to understanding what primordial 鈥榖ricks鈥� we come from,鈥� says of the European Space Agency in Madrid, Spain.
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Dancing dust motes
But these tiny dust grains are difficult to find, as most are blocked by a protective bubble of solar plasma emitted that surrounds the solar system. The Stardust mission to comet Wild 2 returned a handful of interstellar grains, which scientists unveiled in 2014. Now Altobelli and colleagues have used the dust-analysing instrument on Cassini, which has been studying Saturn and its moons since 2004, to find a record 36 particles, mostly made of magnesium, calcium, iron, silicon and oxygen.
The particles were heavily weathered, which suggests they underwent major changes while in interstellar space, Altobelli says. Current wisdom suggests that pristine grains are battered by the process of star and planet-forming, but the new results suggest part of this process happens earlier, he says.
Interstellar bits and pieces
Detecting just 36 dust motes around Saturn was no mean feat 鈥� surrounded as it is by volumes of dust and ice that make up its iconic rings. Determining their origins depends on the path they took. The researchers filtered out any particles containing water, allowing them to discriminate between dust moving around Saturn and particles moving too fast to be orbiting the planet or even the sun, meaning they came from interstellar space.
We are stardust
, an astronomer at the University of California, Berkeley, who is studying the Stardust samples, says the findings will help scientists understand the solar system鈥檚 history.
鈥淲e鈥檙e kind of like archaeologists, looking for ancient fossil hominids. We are trying to understand our own origins,鈥� he says. 鈥淏ut this is even better. This is going even further back, to the original starter stuff of the solar system.鈥�
Journal reference: Science, DOI:
