Tiangong: atoms cooled to 10 picokelvins, a new record
· BehindLines newsroom
Researchers have brought a cloud of atoms down to roughly 10 picokelvins (10 trillionths of a kelvin) aboard China's Tiangong space station. According to Science News and Live Science, which point to a study published on November 5 in the journal Science, it is a record: the cloud forms a condensate colder than all earlier ones, barely above absolute zero (−273.15 °C).
A laser trap in orbit
According to Live Science, 20,000 rubidium atoms were loaded by the team into an optical trap, a kind of "tweezers" made by a laser beam, to restrict their motion. Science News recalls that at the atomic scale temperature is tied to agitation: the more slowly atoms move, the colder they are. In these experiments, an effective temperature is defined from how slowly the cloud spreads out once it is released.
Weightlessness as an ally
According to Science News, gravity makes clouds of atoms sag on Earth, which reduces the effectiveness of cooling. On board the station, the atoms experience microgravity, the sensation of weightlessness felt by an object falling freely. Live Science adds that this setting, combined with the reduced motion, allowed temperatures far lower than those possible on the ground. The resulting cloud is a Bose-Einstein condensate, a quantum phase in which the atoms behave as a single entity, Science News explains.
Earlier records
Science News says that condensates of this kind had already been produced aboard the International Space Station, with effective temperatures as low as 52 picokelvins. An experiment on Earth, in which atoms fell along a tower to reproduce weightlessness, reached 38 picokelvins. The outlet notes that such towers are limited by the duration of the free fall, a constraint that disappears in orbit, so cold-atom experiments in space are taking off.
Why it matters
According to Science News, ultracold atoms are used to study exotic states of matter and to test fundamental principles, such as the equivalence principle, which accounts for bodies of unequal mass falling equally fast in a vacuum. Live Science notes that, according to the team, the result could help future research carried out in space. Both outlets present this figure as the one announced by the study's authors.