Astronomers have discovered what appears to be the oldest known alien world that could be capable of supporting life, and it's just a stone's throw away from Earth.
The newfound exoplanet candidate Kapteyn b, which lies a mere 13 light-years away, is about 11.5 billion years old, scientists say. That makes it 2.5 times older than Earth, and just 2 billion years or so younger than the universe itself, which burst into existence with the Big Bang 13.8 billion years ago.
PHL @ UPR Arecibo, Aladin Sky Atlas
Artistic representation of the potentially habitable world Kapteyn b with the globular cluster Omega Centauri in the background.
"It does make you wonder what kind of life could have evolved on those planets over such a long time," study lead author Guillem Anglada-Escude, of Queen Mary University of London, said in a statement.
Anglada-Escude was referring to Kapteyn b and its newly discovered sister world, Kapteyn c, which both orbit a nearby red dwarf known as Kapteyn's Star. But only Kapteyn b, a "super-Earth" about five times as massive as our own planet, is thought to be potentially habitable; the larger Kapteyn c is likely too cold, researchers said.
The astronomers spotted both alien planets by noting the tiny wobbles their gravitational tugs induced in the motion of Kapteyn's Star. These tugs caused shifts in the star's light, which were first detected using the HARPS spectrometer at the European Southern Observatory's La Silla Observatory in Chile.
The team didn't expect to find a possibly habitable world around Kapteyn's Star, which is one-third as massive as the sun but so close to Earth that it's visible in amateur telescopes, in the southern constellation of Pictor.
"We were surprised to find planets orbiting Kapteyn's Star," Anglada-Escude said. "Previous data showed some moderate excess of variability, so we were looking for very short-period planets when the new signals showed up loud and clear."
Kapteyn b lies in the star's habitable zone, the range of distances that could support liquid water — and thus, perhaps, life as we know it — on a world's surface. The exoplanet completes one orbit every 48 days. The colder Kapteyn c is much farther out, circling the star once every 121 days.
- Mike Wall, Space.com
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First published June 4 2014, 12:08 PM