7 Earth-size planets identified in orbit around a dwarf star

Not just one, but seven Earth-size planets that could potentially harbor life have been identified orbiting a tiny star not too far away, offering the first realistic opportunity to search for biological signs of alien life outside of the solar system.

The planets orbit a dwarf star named Trappist-1, about 40 light-years, or about 235 trillion miles, from Earth.

That is quite close, and by happy accident, the orientation of the orbits of the seven planets allows them to be studied in great detail.

The findings appeared Wednesday in the journal Nature.

One or more of the exoplanets — planets around stars other than the sun — in this new system could be at the right temperature to be awash in oceans of water, astronomers said, based on the distance of the planets from the dwarf star.

“This is the first time so many planets of this kind are found around the same star,” said Michael Gillon, an astronomer at the University of Liege in Belgium and the leader of an international team that has been observing Trappist-1.

They could even discover convincing evidence of aliens.

“I think that we have made a crucial step toward finding if there is life out there,” said Amaury H.M.J. Triaud, an astronomer at the University of Cambridge in England and another member of the research team.

“Here, if life managed to thrive and releases gases similar to that we have on Earth, then we will know.”

Telescopes on the ground and the Hubble Space Telescope in orbit will be able to discern some of the molecules in the planetary atmospheres.

The James Webb Telescope, scheduled to launch next year, will peer at the infrared wavelengths of light, ideal for studying the dimmer longer wavelength light coming from Trappist-1.

Comparisons among the different conditions of the seven will also be revealing.

Even if the planets all turn out to be lifeless, gaining an understanding of the constraints for when life can exist or cannot would also be important new knowledge.