The new technique will help astronomers better understand how galaxies have evolved over billions of years.

Researchers will also be able to collect data on galaxies hosting active black holes and study how they have changed.

"It's exciting to think about how many doors this has unlocked for the future," astronomer Jessica Thorne said.

"The black holes we're looking for are between a million and a billion times more massive than our sun."

They are also very bright and typically found in the centre of the largest galaxies in the universe.

"As they suck in matter from around them, the matter gets super-heated because of friction and becomes very, very luminous," Ms Thorne said.

"And when they're active, these black holes can outshine the rest of the galaxy."

Identifying bright black holes has previously been challenging.

Astronomers have had to look for them using complex methods unique to different types of telescopes.

The new technique uses existing data collected from standard telescope observations of millions of galaxies to find those containing active black holes.

"We can identify these active black holes and look at how much light they are emitting," Ms Thorne said.

Researchers will also be able to measure the properties of the galaxy it is in at the same time.

"By doing both at once we can have a better idea of exactly how the black hole is impacting its host galaxy," Ms Thorne said.

The new technique uses an algorithm called ProSpect, which models emissions from galaxies and black holes at different wavelengths of light.

The method has already been applied to almost half a million galaxies from Anglo-Australian Telescope's Deep Extragalactic VIsible Legacy Survey.

It has also been used on data from more than 200,000 galaxies from the Galaxy and Mass Assembly survey, which brings together observations from six of the world's best ground and space-based telescopes.

Astronomer Sabine Bellstedt said scientists had often ignored researching bright black holes in galaxies because they were hard to find.

"We do not really understand these bright black holes to incorporate them into our modelling with sufficient detail," she said.

The new technique makes it much easier. It is also more consistent and thorough.

"It suddenly means we can look for active black holes in so many more places than we were able to before," Dr Bellstedt said.

"It's going to help us search more galaxies, and look further back in time to the distant universe."

Supermassive black holes are thought to have a huge impact on how galaxies evolve.

"We think that an active black hole in a galaxy is able to decrease the amount of star formation really quickly and stop the galaxy from growing any further," Ms Thorne said.

"It can effectively kill it."

The research was published in Monthly Notices of the Royal Astronomical Society.

The International Centre for Radio Astronomy Research team are jointly supported by the Curtin University and the University of Western Australia.

Australian Associated Press