Galaxies are running out of gas, causing the universe to form fewer stars, according to technology blog TG Daily. The reason behind the star deficiency is a shortage of molecular hydrogen, an Australian research team explained.

Astronomers have long known that the rate at which stars form reached its peak when the universe was only a few billion years old, suggesting that our universe is past its prime.

Dr. Robert Braun of CSIRO and his team used the Mopra radio telescope in order to compare distant, older galaxies to our neighborhood galaxies. The team found that galaxies between three and five billion years old are equipped with more molecular hydrogen gas, which enables galaxy formation.

Our result helps us understand why the lights are going out, Braun said. Star formation has used up most of the available molecular hydrogen gas, he added.

Braun also said that galaxies lose considerable amounts of gas as they become older and in events such as supernovae. 

Galaxies are refueled when gas falls inside of them from the intergalactic medium, the space between them. 

The drop-off in both gas availability and star formation seems to have started around the time that Dark Energy took control of the universe, Braun said. Braun also said that Dark Energy has taken over our universe, causing it to rapidly expand and making it harder for galaxies to find needed gas.