An international research team at the Center for Rare Isotope Beams (FRIB) at Michigan State University has successfully created five new isotopes by moving stars closer to Earth.

The isotopes known as thulium-182, thulium-183, ytterbium-186, ytterbium-187 and lutetium-190 were reported in the journal Feb. 15. Physical Examination Letters.

These represent the first new set of isotopes produced at the U.S. Department of Energy’s Office of Science, or FRIB, DOE-SC, which supports the mission of the DOE-SC Office of Nuclear Physics. The new isotopes show that FRIB is close to creating nuclear samples that currently only exist when superdense celestial bodies known as neutron stars collide together.

“This is the exciting part,” said Oleksandra Gade, professor of physics at FRIB and scientific director of the MSU College of Physics and Astronomy and FRIB. “We are confident that we can get even closer to the nuclei that are important for astrophysics.”

Gade is also one of the speakers on the project, led by Oleg Tarasov, senior research physicist at FRIB.

The research team included a group from FRIB and MSU, as well as staff from the Institute for Basic Sciences in South Korea and RIKEN in Japan; The abbreviation stands for Physical and Chemical Research Institute.

“This is probably the first time these isotopes have existed on the Earth’s surface,” said Bradley Sherrill, professor emeritus at MSU’s School of Life Sciences and head of the Advanced Rare Isotope Separator at FRIB.

To explain what “advanced” means in this context, Sherrill said researchers needed only a few individual particles to confirm the existence and identity of a new isotope with FRIB’s state-of-the-art instruments.

Researchers now know how to produce these new isotopes and can begin producing them in larger quantities to perform experiments that were not possible before. Researchers are also trying to follow their lead to create new isotopes that are much more similar to those found in stars.

“I like to use the analogy of a road trip. We were looking forward to going somewhere we’ve never been before, and that’s the first step,” Sherrill said. “We leave the house and start exploring.”

Almost a star

Our sun is a cosmic atomic factory. It is powerful enough to take the nuclei of two hydrogen atoms or nuclei and turn them into a single helium nucleus. Hydrogen and helium are the first and lightest entries in the periodic table of elements. Reaching the heavier elements on the table requires a much denser environment than can be found in the sun. Scientists suggest that elements such as gold with a mass approximately 200 times greater than hydrogen were formed by the merger of two neutron stars.

Neutron stars are the remnants of the cores of exploded stars that were initially much larger than our Sun, but not large enough to become black holes in their final movements. Although neutron stars are not black holes, they still have a huge mass in very small sizes.

“With the mass of our sun, they are about the size of Lansing,” Sherrill said. “It’s unclear, but people think all the gold on Earth is created by neutron star collisions.”

By creating isotopes present in the neutron star collision zone, scientists were able to better investigate and understand the processes involved in the formation of these heavy elements. The five new isotopes aren’t part of this environment, but they’re the closest scientists have come to reaching this particular region, and there’s a very good chance they’ll eventually get there.

To create the new isotopes, the team directed a beam of platinum ions at a carbon target. The beam current divided by the state of charge was 50 nanoamperes. Since conducting these experiments, FRIB has increased the power of the beam to 350 nanoamps and plans to reach 15,000 nanoamps. Meanwhile, new isotopes are exciting in their own right and open new opportunities for the nuclear research community to step into the unknown.

“It’s not surprising that these isotopes exist, but now that we have them, we have colleagues who will be very interested in what we can measure next,” Gade said. “I’m starting to think about what we can do next in terms of measuring their half-lives, their masses, and other properties.”

Probing these quantities in isotopes that have never existed before will inform and improve our understanding of basic nuclear science.

“There’s still a lot to learn,” Sherrill said. “And we’re on our way.”