Doyle Rice

USA TODAY

Our science fiction dreams of Martians may never come true, but three earth-like planets discovered orbiting a nearby star have potential life and water, astronomers announced Monday.

The sizes and temperatures of these worlds are similar to those of Earth and Venus, and hold the best promise yet for the search for life outside the solar system. All three planets may have regions with temperatures that are within a range suitable for sustaining liquid water and life, according to the report published Monday in the British journal Nature.

The three planets orbit around an "ultracool" dwarf star just 40 light-years from Earth, or some 240 trillion miles away. In astronomical terms, that's pretty close considering our own Milky Way galaxy spans 100,000 light years.

'Toasty' exoplanet resembles Earth but for oven-like temperature

Since the planets are outside our solar system, they are called exoplanets.

"This really is a paradigm shift with regards to the planet population and the path towards finding life in the Universe," said Emmanuël Jehin, a co-author of the new study and an astronomer at the University of Liège in Belgium.

"So far, the existence of such 'red worlds' orbiting ultra-cool dwarf stars was purely theoretical, but now we have not just one lonely planet around such a faint red star but a complete system of three planets," he said.

Astronomers spot young, 'Jupiter-like' planet

The group of international astronomers from MIT, NASA, the University California at San Diego, the University of Liège and other institutions made the discovery. Astronomers focused the Belgian TRAPPIST telescope on the star now known as TRAPPIST-1, a Jupiter-sized star in the constellation Aquarius that is one-eighth the size of our sun and significantly cooler.

The new planets were detected by the faint dimming of the star as the planets orbited, blocking some of its light.

Despite being so close to the Earth, the star is too dim and too red to be seen with the naked eye or even with a large amateur telescope.