First space-based measurement of neutron lifetime

(11 June 2020)

MESSENGER spacecraft in orbit at Mercury. Credit: NASA/Johns Hopkins University Applied Physics Laboratory/Carnegie Institution of Washington

Our researchers have helped to find a way of measuring neutron lifetime from space for the first time.

The discovery could teach us more about the early universe as knowing the lifetime of neutrons is key to understanding the formation of elements after the Big Bang 13.8 billion years ago.

Scientists used data from NASA’s MErcury Surface, Space ENvironment, GEochemistry, and Ranging (MESSENGER) spacecraft.

Neutron particles

As MESSENGER flew over Venus and Mercury it measured the rates at which neutron particles were leaking out from the two planets.

The number of neutrons detected depended on the time it took them to fly up to the spacecraft relative to the neutron lifetime, giving the scientists a way of calculating how long the subatomic particles could survive.

Neutrons are normally found in the nucleus of an atom but quickly disintegrate into electrons and protons when outside the atom.

Space mission

Scientists have previously used two lab-based methods – the so-called “bottle method” and “beam” technique - to try and determine the lifetime of neutrons.

This latest research could provide a route to end a decades-long stalemate that has seen scientists disagree – by a matter of seconds – over how long neutrons are capable of surviving.

Researchers behind this study say that more precise measurements would require a dedicated space mission, possibly to Venus, as its thick atmosphere and large mass trap neutrons around the planet.

They hope to design and build an instrument that can make a high-precision measurement of the neutron lifetime using their new technique.

Find out more

• Read the full research paper in Physical Review Research.

• The study was carried out by Dr Vincent Eke and Dr Jacob Kegerreis in our Institute for Computational Cosmology, and was led by Johns Hopkins Applied Physics Laboratory, USA.

• NASA’s MESSENGER mission.

• Undergraduate and postgraduate study in Physics at Durham.

• The research was funded by the US Department of Energy Office of Nuclear Physics, the Science and Technology Facilities Council (STFC), and the ICC PhD Scholarships Fund.