US, WASHINGTON (ORDO NEWS) — For the first time, scientists measured the life span of a neutron in outer space.
You see, with a safe location in the nucleus of an atom, subatomic particles, which we call neutrons, have a fairly stable existence. After ejection from this nucleus, the life span of a neutron is much shorter.
How short is it? Well, we don’t know for sure, because our measurement methods give two different results – but scientists would really like to resolve the issue. A new method for measuring neutrons in space can help solve a mystery.
In turn, this could help us better understand how quickly the elements formed from the “soup” of particles that filled the Universe immediately after the Big Bang, about 13.8 billion years ago.
This process is known as the Big Bang Nucleosynthesis and is thought to have occurred between 10 seconds and 20 minutes after the Big Bang. Knowing how long neutrons can survive on their own will allow cosmologists to limit the upper limit of this period.
“The first time anyone has measured the neutron lifetime in space,” said planetary scientist Jack Wilson of Johns Hopkins University’s Applied Physics Laboratory, lead author of an article describing new results.
Since the 1990s on Earth, two different classes of experiments have been used to measure neutron lifetime: “bottle” and “beam”.
In bottle methods, scientists create a trap — mechanical, gravitational, magnetic, or a combination of them — and measure how long it takes the neutrons inside to decay.
In radiation methods, scientists launch a neutron beam and count the protons and electrons that are produced as a result of neutron decay.
Both of these methods are very accurate, but there is a problem. Bottle methods, on average, show a decay time of 879.5 seconds, or 14 minutes and 39 seconds, with an error of 0.5 seconds. Radiation with an average value of 888 seconds, or 14 minutes and 48 seconds, with an error of 2 seconds.
This 9-second difference between the two averages may not seem too big, but when you try to narrow the neutron’s lifetime it is huge. And here outer space appears.
Between 2011 and 2015, NASA’s MESSENGER spacecraft revolved around Mercury, and the route was difficult, involving two Venus overflights and three Mercury overflights.
As it approached Venus, the MESSENGER neutron spectrometer collected data on neutrons emitted from the planet at a speed of several kilometers per second.
At an altitude of 339 kilometers, MESSENGER was close to the maximum distance that these neutrons could travel before decay. Similar measurements were taken during the flight of Mercury at a minimum altitude of 205 kilometers.
“It’s like a big bottle experiment, but instead of walls and magnetic fields, we use Venus’s gravity to hold neutrons for a time comparable to their lifetime,” Wilson said.
To calculate the neutron lifetime, the team modeled how many neutrons they should detect at altitudes of Venus’s flight for a lifespan range of 10 to 17 minutes. According to this model, a lifespan of about 780 seconds – 13 minutes – was the best.
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