The researchers said the findings were made possible by a first-of-its-kind telescope imaging system that allowed the astronomers to pick out the planets amidst the bright glare of their parent star and measure their spectra, the rainbows of light that reveal the chemical signatures of planetary atmospheres.
"These warm, red planets are unlike any other known objects in our universe," study lead author Ben R. Oppenheimer, an astronomer at the American Museum of Natural History, said. "And the planets are very different from one another as well. All four planets have different spectra and all four are peculiar."
Previous images of these four planets, which orbit a star called HR 8799 located 128 light years away, have been recorded but because a star's light is tens of millions to billions of times brighter than the light from that star's own planets, distinguishing planet light from starlight so as to directly measure the spectra from the planets alone is difficult, the researchers said.
But a new device fitted to the Hale Telescope at Caltech's Palomar Observatory in Southern California blocks the otherwise overwhelming starlight, picks out the faint specks that are planets, and obtains their spectra, they said.
And what the spectra of their four planets show is that they are quite strange, Caltech astronomy Professor Lynne Hillenbrand said.
"A remarkable thing about these planets is their unexpected spectroscopic diversity," she said.
Further study is needed to further explore this solar system's unusual characteristics, researchers said.
"The spectra of these four worlds clearly show that they are far too toxic and hot to sustain life as we know it," said study co-author Ian Parry, a senior lecturer at the Institute of Astronomy at Cambridge University in Britain. "But the really exciting thing is that, one day, the techniques we've developed will give us our first secure evidence of the existence of life on a planet outside our solar system."