Researchers have found that all living organisms emit a faint glow which disappears when they die.

This glow uncovered in the fresh study is linked to metabolic processes, the chemical reactions that keep cells and organisms alive.

One key by-product of metabolism is a group of molecules called reactive oxygen species (ROS).

A team of scientists from Canada's University of Calgary said when too many ROS are produced, it can cause oxidative stress, triggering electron transfer between chemicals in the body.

Researchers have found that all living organisms emit a faint glow which disappears when they die

Researchers believe this process is connected to the faint glow emitted by all living beings.

The study published in The Journal of Physical Chemistry Letters investigates the mysterious glow, known as ultraweak photon emission (UPE), in mice.

The researchers observed that live mice emitted much stronger UPE signals than those that had recently died, confirming a link between the glow and life.

In plants, the glow also varied depending on stress factors such as changes in temperature, physical injury or exposure to chemicals.

The researchers observed that live mice emitted much stronger UPE signals than those that had recently died

The faint glow has been observed in a host of life forms, from single-cell organisms and bacteria, all the way up to humans.

The light sits between 200 to 1,000 nanometres in the spectral range and is invisible to the human eye.

However, scientists still know little about how death or stress affects UPE.

The latest study from the University of Calgary compared the glow in living and recently deceased animals, while also examining how temperature changes, injury and chemical treatments influenced UPE in plants.

The latest study from the University of Calgary researchers compared the glow in living and recently deceased animals

To study the glow, scientists built dark enclosures to block out all environmental light and used special cameras to capture emissions from both plants and animals.

Researchers observed that live mice produced noticeably strong light, while the faint glow from recently euthanised mice had almost disappeared, despite maintained the same body temperature.

In the study, scientists wrote: “Our investigation reveals a significant contrast between the UPE from live vs dead mice.

“In plants, we observed that an increase in the temperature and injuries both caused an increase in UPE intensity.”

Chemical treatments also changed how plants emitted the faint glow.

Researchers found that applying a local anaesthetic to an injured area of a plant produced the strongest light emission of all the compounds they tested.

The authors also hoped their findings help pave the way for UPE imaging in future research and clinical diagnostics.

The scientists wrote: “UPE imaging provides the possibility of non-invasive label-free imaging of vitality in animals and the responses of plants to stress."