Scientists have discovered that an Earth-sized planet outside our solar system has its own atmosphere.

It is the first such discovery around a low-mass rocky planet, marking an important step in our understanding of the potential for life on other worlds.

"The detection of an atmosphere around the super-Earth GJ 1132b marks the first time that an atmosphere has been detected around an Earth-like planet other than Earth itself," said lead author John Southworth from Keele University in England, whose research was published in The Astronomical Journal.

The planet, which is 1.4 times the diameter of Earth and 1.6 times its mass, is orbiting a red dwarf star just 12 parsecs, or 39 light years, away.

While the star is a relatively cool 3000 degrees – almost half the temperature of the sun – the planet orbits just 2.3 million kilometres away, making its temperature a steamy 370 degrees.

"We simulated a range of possible atmospheres for this planet, finding that those rich in water and/or methane would explain the observations," Dr Southworth said.

"The planet is significantly hotter than Earth, so one possibility is that it is a 'water world' with an atmosphere of hot steam."

"This is really exciting stuff," said Lucyna Chudczer, a research fellow in astronomy at the University of NSW. "We are just scratching the surface of exoplanet discoveries; there will be a lot more coming soon."

Dr Chudczer said GJ 1132b was not likely a planet where life as we understand it could emerge, as atmospheric pressure would need to be very high for water to be liquid.

"However, it is very encouraging that an atmosphere has lasted so long on a planet around such a star," she said.

The planet's host star is about 5 billion years old, so GJ 1132b is likely a similar age to Earth, Dr Chudczer said.

According to the exoplanet database operated by the Paris Astronomical Data Centre, there are now more than 3600 confirmed exoplanets – many in multiplanetary systems. There is data for thousands more candidate objects for scientists and citizen scientists to study.

New technology and increased data collected from stars has seen a huge growth in the discovery of exoplanets, including more recent involvement of "citizen scientists".

On ABC's Stargazing Live program on Thursday night, Darwin mechanic Andrew Grey was announced as the first to find information revealing a new four-planet solar system 600 light years away.

He had been looking through new data from the Kepler space telescope on the Exoplanet Explorers site.

Mr Grey told the ABC: "[I'm] just glad that I can contribute. It feels very good.

"The first night I jumped on ... I catalogued 1000 [objects], so I punched a few out," he said.

While the method of discovery was notable, it was unclear how significant the find was scientifically.

"These sorts of exoplanet discoveries are as common as dirt nowadays," said Professor Chris Tinney, head of exoplanetary science at the University of NSW.

"It's another multiplanetary system to add to the many hundred we have found in the Kepler data."

Professor Sarah Maddison, head of the planets group at Swinburne University, said it was exciting to have citizens involved.

"We are finding so many interesting planets around distant stars that we need all the help we can get," she said.