An experiment currently on the International Space Station (ISS) has reached an incredibly low temperature, just a fraction of a degree above absolute zero, setting a new record for the lowest temperature ever achieved in space.
The experiment is the Cold Atom Laboratory (CAL) and its goal is to create a state of matter like no other, referred to as the fifth state of matter as it differs from liquids, gases, solids, and plasma: a Bose-Einstein Condensate (BEC). This is the first ever BEC produced in orbit.
A BEC is a particular state of matter that only happens when a low-density gas is cooled to ultra-low temperatures; atoms behave more like waves than particles in these conditions. The wave nature of matter is only typically observable in the minutest scales, but in a BEC this is macroscopic. The atoms begin to act like a single wave, becoming indistinguishable from one another. Studying this system is telling us what physics is like at its extremes.
"Having a BEC experiment operating on the space station is a dream come true," Robert Thompson, CAL project scientist from NASA's Jet Propulsion Laboratory, said in a statement. "It's been a long, hard road to get here, but completely worth the struggle, because there's so much we're going to be able to do with this facility."
CAL has reached temperatures of about 100 nanokelvins, significantly colder than outer space, which is at 3 Kelvins (-270.15°C/ -454.27°F) but not yet close to experimental records reached on Earth. The team has their eyes on those temperatures but there is a more important advantage in being in space: the BECs are longer-lived so can be studied for longer.
BECs are created within atom traps, created using magnetic fields or lasers. Low-density gas within the traps experiences decompression cooling as the atoms trap expand. The longer the gas is in the trap the cooler it gets. On Earth, because of gravity, BECs can only be studied for a fraction of a second. CAL allows for individual BECs that last between 5-10 seconds, and it's possible to repeat the experiment for up to six hours a day.
"CAL is an extremely complicated instrument," added Robert Shotwell, chief engineer of JPL's astronomy and physics directorate. "Typically, BEC experiments involve enough equipment to fill a room and require near-constant monitoring by scientists, whereas CAL is about the size of a small refrigerator and can be operated remotely from Earth. It was a struggle and required significant effort to overcome all the hurdles necessary to produce the sophisticated facility that's operating on the space station today."
CAL is currently in its commissioning phase, still being tested. It will start science operations in September and there are many scientists worldwide queueing up to use it over the next three years.