Why should NASA take photos from space

Matter research in space : Extreme form of matter generated on the International Space Station

The International Space Station (ISS) last made headlines when the Americans flew astronauts there again for the first time in almost a decade, and in Germany when Alexander Gerst was in command of the human outpost that circled 400 kilometers above the earth.

Now the station is delivering a scientific highlight: the production of a Bose-Einstein condensate in orbit, which physicists are now reporting on in the specialist journal "Nature".

A Bose-Einstein condensate is an extraordinary form of matter. In order to produce them, atoms are cooled to almost absolute zero, to a temperature close to 273 degrees Celsius below zero.

Quantum research and sensors

This massively slows down the movements of the atoms. If they are faster than sound at room temperature, they are slower than a snail near absolute zero. And they show a strange behavior: they give up their independence and form a kind of superatom in which everyone takes on the same physical properties. Instead of fidgeting around chaotically, they march in lockstep, so to speak. The atomic cloud behaves like a wave of matter. Effects from the quantum world become visible and can be researched.

The experiments in weightlessness enable advances in quantum research. Possible applications are, for example, highly sensitive sensors that detect raw materials, changes in the groundwater or cavities in the underground without contact, or make navigation more precise than it is today.

In order to produce a Bose-Einstein condensate, extensive structures are required. First, the fast atoms are slowed down using a laser. Then particularly high-energy atoms are removed so that only the slow ones remain and form the desired condensate.

After this was first achieved 25 years ago, research groups have now become quite routine. But there is a problem: the force of gravity destroys the special state of matter after a fraction of a second and limits research. If it is to be maintained longer, one would have to go into weightlessness.

17 billionths of a degree above zero

With this goal in mind, the “Cold Atom Lab” at NASA's Jet Propulsion Laboratory (JPL) was built. The engineers had to design the high-tech devices in such a way that they could survive a rocket launch and could be controlled from the JPL in orbit - and put everything in a refrigerator-sized container. In May 2018, the Cold Atom Lab was finally ready and brought to the ISS.

As in laboratories on earth, the Bose-Einstein condensate is generated in a magnetic trap and the magnetic field is then switched off to begin the investigations. If the force of gravity is active, the special condition is over after a few hundredths of a second and the cloud disintegrates.

As Robert Thompson from JPL and his team are now reporting, the Bose-Einstein condensate of rubidium atoms held in Earth orbit for more than a second and expanded much more slowly than comparable atomic clouds on Earth. A temperature of 17 nanokelvin was reached, that is 17 billionths of a degree Celsius above absolute zero.

Those involved in the Cold Atom Lab believe that even lower temperatures can be reached in the future and that the Bose-Einstein condensate could last for up to 20 seconds - which will further improve research opportunities.

Mass changes, raw materials and navigation

Maike Lachmann from the Institute for Quantum Optics at the University of Hanover wrote in an accompanying comment in “Nature” that the team succeeded in creating a “masterpiece” that was not only a “technological milestone” but could also improve basic physical understanding: Atomic interferometers could use the wave properties of atoms and record extremely small differences in gravity.

The sensitivity of an atomic interferometer increases exponentially with the life of the Bose-Einstein condensate. A wide variety of applications are conceivable, from basic research on dark matter and dark energy to the detection of mass changes in the subsurface, which can occur due to fluctuating amounts of groundwater or magma flows. The search for raw materials or cavities under the surface, which as surprising sinkholes are also dangerous in this country, is part of it. Last but not least, atomic interferometers promise a clear specification of navigation systems.

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