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Raumfahrt - ESA: Making planets in a rocket

16.11.2019

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How are celestial bodies created? Aside from philosophical questions, researchers are taking practical steps to investigate the very first moments when planets are born – on a sounding rocket launching from Sweden next week.

Astronomers conclude that planets are formed out of cosmic dust and gas from an interstellar cloud around a new-born star, but exactly how dust particles start to assemble into larger celestial bodies is still a mystery.

Go back far enough in time and Earth will not have existed, but its formation must have started somewhere, sometime. And this very first clumping together of dust particles in zero gravity will be investigated in the ICAPS experiment.

planet-drop-pillars

This video shows silicon dioxide – also called silica – dust particles being shot into a vacuum chamber in weightlessness to observe their growth, how they interact and stick together. The video was recorded during a drop tower experiment at the Zarm tower in Germany and played back at five times reduced speed.

Astronomers conclude that planets are formed out of cosmic dust and gas from an interstellar cloud around a new-born star, but exactly how dust particles start to assemble into larger celestial bodies is still a mystery.

Go back far enough in time and Earth will not have existed, but its formation must have started somewhere, sometime. And this very first clumping together of dust particles in zero gravity will be investigated in the ICAPS experiment.

Drop tower experiments allow for up to nine seconds of microgravity but the ICAPS team behind this experiment are aiming for more with a sounding rocket session that will allow researchers to watch up to six minutes of planet formation in progress.

The experiment aims to simulate growth of micrometre-sized particles – similar in size to talcum powder – to millimetre-sized aggregates and investigate the physical phenomenon of Brownian motion. This process is believed to be the main mechanism of how “planet embryos” evolved in the young Solar System.

The dramatic movement seen in the particles occurred when the "cloud manipulation system" that is part of ICAPS was switched on. This device keeps the dust cloud in place and also "squeezes" it. By toggling the cloud manipulation system on and off for roughly half of the time in weightless the researchers can compare how the dust aggregates form and better understand the difference when Brownian motion applies.

These experiments will provide insight into how dust first starts to clump together, and so into the very early stages of planet formation.

Researchers will shoot silicon dioxide – also called silica – dust particles into a vacuum chamber and observe their growth, how they interact and stick together.

“It is a bit like hosting a party where you want people to mingle and interact”, likens Astrid Orr of ESA’s SciSpacE team. “We are trying to create the ideal conditions for small groups to form by adjusting the style of the room, or playing the right music – in this case we are adjusting the conditions in the experiment chamber,  relative speed of the particles and especially particle concentration.

“Like making a snowman, you need the right snow.”

ICAPS experiment in Zarm drop tower
ICAPS experiment in Zarm drop tower

The ICAPS experiment is a 1.2-m-long module that houses the vacuum chamber, an injector of silica particles, and cameras to observe their interaction. The experiment has ‘flown’ with promising results in the ZARM drop tower in Bremen, Germany, but scientists want to observe the process for longer.

Drop tower experiments allow for up to nine seconds of microgravity whereas sounding rockets will allow researchers to watch up to six minutes of planet formation in progress.

The experiment aims to simulate growth of micrometre-sized particles – similar in size to talcum powder – to millimetre-sized aggregates and investigate the physical phenomenon of Brownian motion. This process is believed to be the main mechanism of how “planet embryos” evolved in the young Solar System.

Birth of a planet
Birth of a planet

“When you see dust moving in sunlight, the tumbling motion of the small dust is in part due to Brownian motion.” explains Astrid. “The Brownian model describes the movement of particles suspended in a gas or a liquid, but on Earth gravity also influences the movement and makes it hard to create a pure laboratory model of Brownian motion.”

The ICAPS experiment will provide insight into the very early stages of planet formation. Meanwhile, ESA’s exoplanet satellite Cheops – scheduled for launch in mid-December – will study the end result of this process: planets outside our Solar System typically orbiting other stars and known as exoplanets.

Quelle ESA

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