In 1995, researchers were able to prove that a fifth state of matter — the Bose-Einstein condensate — could be created at very low temperatures. Until recently, this state of aggregation could only be generated using high-vacuum apparatus on Earth and was the state was extremely short-lived due to gravity. However, a German research team has now succeeded in generating and studying the Bose-Einstein condensate using an unmanned space rocket.
In addition to the standard aggregate states of solid, liquid, and gas, matter can also have other states.
A gas, for example, can be ionised at high temperatures to form a plasma.
In 1995, researchers were able to prove that a fifth state of matter could be created at very low temperatures — the Bose-Einstein condensate.
In quantum mechanics, the Bose-Einstein condensate is used to conduct quantum experiments. For example, it can be used to study gravitational waves or the Earth's gravitational field.
Until now, however, this special state of aggregation could only be generated using high-vacuum apparatus on Earth and the state was extremely short-lived due to gravity.
A German research team has now succeeded for the first time in generating and studying the Bose-Einstein condensate on board an unmanned space rocket — they published the results of their researched in journal Nature.
The duration of experiments is limited by gravity
The formation of such a condensate at extremely low temperatures was first predicted by the two physicists Satyendranath Bose and Albert Einstein.
Researchers detected the Bose-Einstein condensate after cooling atoms to a temperature only one millionth of a degree above absolute zero (0 Kelvin).
Have you read?
As the atoms are cooled, the movement of atoms decreases and, at the same time, the wavelength of the particles increases. Near absolute zero, an almost complete standstill is reached and the wave functions (each particle is described in quantum mechanics with its own wave function) of the individual particles overlap. In this state, all atoms in the system have the same physical properties — they behave like a single atom or a superatom.
Although experiments with Bose-Einstein condensates are extremely useful, they have so far proved difficult to carry out: due to the gravitational forces acting on the atoms in the condensate cloud, they fall down in a very short time and experiments can't continue.
In order to be able to study the cold condensate cloud for longer, researchers therefore use very high drop towers. In this way, the duration of the experiments can be extended.
But even very tall drop towers such as the 122-metre tower in Bremen, you can only achieve free-fall in weightlessness for a few seconds — or as we call it, microgravity," explained Maike Lachmann from the University of Hanover in World of Physics. "In space, on the other hand, much longer and more precise measurements can be made".
In order to conduct experiments with Bose-Einstein condensates in space, researchers developed a chip made of rubidium atoms and, in January 2017, transported it aboard space rocket MAIUS-1 from Esrange Space Center.
Once in space, the temperature of the atoms was reduced by laser and evaporative cooling until the condensate formed. The researchers were then able to investigate how the atomic gas behaved when manipulated in different ways. During its boost phase and six-minute space ﬂight, 110 experiments were performed.
In 2020 and 2021, further experiments will be carried out, including experiments with potassium atoms. Researchers from the German Aerospace Center (DLR) and NASA will use the findings of the German researchers in future for their own research on cold quantum gases aboard the ISS.