LULU GARCIA-NAVARRO, HOST:
This is Lulu's log, stardate Feb. 11, 2018, where we explore matters of space, the stars, and the universe.
(SOUNDBITE OF C418'S "MOOG CITY")
GARCIA-NAVARRO: We like to think we're not alone in the universe. It stands to reason, after all, there are billions of galaxies and solar systems out there. But this week, researchers discovered evidence of planets outside our galaxy. How far out there, though? We asked Eddie Guerras, a postdoctoral researcher at the University of Oklahoma who made the finding.
EDDIE GUERRAS: The light that comes from the sun takes eight minutes to arrive to Earth, and the light from the moon takes one second.
GARCIA-NAVARRO: But these newly discovered planets?
GUERRAS: Four billion light years.
GARCIA-NAVARRO: Because of how far away they are, his team found them indirectly with a technique called gravitational lensing.
GUERRAS: That's a system in which you have a very far away source of light and something in between, just in the line of sight. It's a very happy coincidence. And that something in between is a big galaxy that distorts the light.
GARCIA-NAVARRO: We already knew that there were galaxies outside our own, but Guerras' team identified a group of planets inside one of those other galaxies for the first time. Guerras thinks the planets are between the sizes of the moon and Jupiter, but because they're so far away, we'll probably never actually see them.
GUERRAS: There is a limit to our knowledge and a limit to the portion of space and time we can explore. It's a big curtain because we got to look behind that for physical reasons.
GARCIA-NAVARRO: So even as we continue to expand our understanding of the universe, it turns out there actually is a limit to what we can know.
(SOUNDBITE OF C418'S "MOOG CITY") Transcript provided by NPR, Copyright NPR.