Deep beneath the mountains of Japan, scientists are preparing a powerful instrument that may soon reveal signals from stars that died billions of years ago. With a major upgrade to a huge underground detector, astronomers hope to observe ghost particles released during ancient stellar explosions.
These particles come from supernovas, the violent deaths of massive stars. Although such explosions shine brightly, the light shows only a small part of the event. Most of the energy escapes in the form of ghost particles known as neutrinos.
Because these particles rarely interact with matter, they travel through space almost untouched. As a result, many have journeyed across the universe for billions of years before reaching Earth.
Ancient stellar explosions leave hidden signals
Sometimes a star suddenly erupts in an intense flash of light. For a short time, the burst can outshine an entire galaxy. However, this spectacular ending happens only to very massive stars.
Astronomers estimate that fewer than one percent of stars possess enough mass to explode as supernovas. These stars must contain at least eight times the mass of the Sun.
Observers have witnessed such explosions for centuries. In 1572, Danish astronomer Tycho Brahe recorded a supernova so bright that people could see it without telescopes for two years.
However, visible light tells only a small part of the story. During a supernova, roughly ninety nine percent of the energy leaves as ghost particles rather than light.
Underground detector seeks ghost particles
Scientists hope to detect these elusive signals using the Super Kamiokande detector in Japan. The telescope sits deep underground inside a massive chamber filled with specialised sensors.
Researchers recently upgraded the facility to improve its sensitivity. Because of this improvement, the detector may soon capture extremely faint signals from distant stellar explosions.
For particle astrophysicists, this possibility is remarkable. The detector may reveal the combined glow of ghost particles produced by countless supernovas across cosmic history.
These particles carry information from stars that died long before Earth formed. Some have travelled for more than ten billion years before arriving here.
Clues about what remains after a star dies
Astronomers still debate what remains after a massive star collapses. In some cases, the core may become a black hole. In others, it may form a neutron star.
A neutron star is extremely dense yet very small. Despite containing enormous mass, it measures only about twenty kilometres across.
If scientists detect the collective signal of supernova ghost particles, they may answer important questions about these outcomes. The data would also reveal how massive stars lived and died throughout the history of the universe.
Although supernovas occur rarely in the Milky Way, they happen frequently across the wider cosmos. On average, one massive star explodes somewhere in the universe every second.
Therefore, ghost particles from these events constantly stream through space. Even now, countless particles pass through Earth and through every person without leaving a trace.
However, with the upgraded underground detector, scientists may finally catch them. If researchers confirm the signal, astronomy could enter a new era of discovery.