Millions of years ago, a massive star exploded somewhere far away in our galaxy.
During this violent event, called a supernova, the dying star blasted huge amounts of matter into space.
These materials included carbon, nitrogen and oxygen—the essential ingredients for life—as well as many other elements, some as heavy as iron.
The explosion itself lasted only a short time, but the particles it launched into space are still traveling today.
Some of them are only now reaching Earth after journeys that have taken millions of years.
These fast-moving particles are known as cosmic rays. Unlike X-rays or ultraviolet rays, which are forms of energy, cosmic rays are actual particles that race through space at nearly the speed of light.
They contain a variety of elements, including phosphorus, chlorine, potassium, argon and calcium.
Scientists are fascinated by cosmic rays because they carry clues about how stars explode and how matter moves through the universe.
One long-standing mystery is why these particles are still traveling so fast.
The initial blast from a supernova should have slowed down over time, suggesting that some unknown process may be accelerating them during their journey.
To investigate these questions, scientists rely on the Alpha Magnetic Spectrometer, or AMS-02, a particle detector attached to the International Space Station. Since it was installed in 2011, AMS-02 has spent more than 13 years collecting data in space.
Its location above Earth’s atmosphere is crucial. Our atmosphere protects us from cosmic rays, but it also prevents scientists from measuring them accurately from the ground. By operating in orbit, AMS-02 can directly detect these particles as they arrive from space.
Over the years, the instrument has recorded an astonishing 230 trillion cosmic ray events. Most involve common elements such as hydrogen and helium.
However, a tiny number involve heavier elements such as iron, nickel and zinc, making these rare events especially valuable to researchers.
By analyzing the particles’ properties, scientists can identify their parent elements and learn how the particles were created and traveled across the galaxy.
The latest findings have revealed something unexpected. Researchers found that the 20 elements they studied can be divided into four distinct groups of cosmic rays.
Some elements belong mainly to primary cosmic rays. These particles travel relatively directly from their sources in deep space. Others belong mostly to secondary cosmic rays, which have collided with gases between stars and become mixed with other particles during their journey.
The researchers identified two groups of primary cosmic rays and two groups of secondary cosmic rays. The way these elements naturally organize themselves into four separate classes does not match current scientific theories.
This is particularly important because the AMS-02 measurements are extremely precise. The unexpected patterns suggest that scientists may be missing an important piece of the puzzle about how cosmic rays are formed, accelerated and spread throughout the universe.
The Alpha Magnetic Spectrometer continues to uncover surprises from particles created by stars that died millions of years ago. By studying these ancient messengers from deep space, scientists hope to gain a deeper understanding of stars, matter and the fundamental workings of the cosmos itself.
