Two huge planets found orbiting a star 375 light-years away are the oldest alien worlds yet discovered, scientists say.

With an estimated age of 12.8 billion years, the host star—and thus the planets—most likely formed at the dawn of the universe, less than a billion years after the big bang.

"The Milky Way itself was not completely formed yet," said study leader Johny Setiawan, who conducted the research while at the Max-Planck Institute for Astronomy in Heidelberg, Germany.

Physicists struggling to reconcile gravity with quantum mechanics have hailed a theory – inspired by pencil lead – that could make it all very simple

IT WAS a speech that changed the way we think of space and time. The year was 1908, and the German mathematician Hermann Minkowski had been trying to make sense of Albert Einstein's hot new idea - what we now know as special relativity - describing how things shrink as they move faster and time becomes distorted. "Henceforth space by itself and time by itself are doomed to fade into the mere shadows," Minkowski proclaimed, "and only a union of the two will preserve an independent reality."

And so space-time - the malleable fabric whose geometry can be changed by the gravity of stars, planets and matter - was born. It is a concept that has served us well, but if physicist Petr Horava is right, it may be no more than a mirage. Horava, who is at the University of California, Berkeley, wants to rip this fabric apart and set time and space f

Pick up a 30-year-old astronomy textbook and you will find more illustrations of planets than actual pictures; Pluto still holds onto its full planet status and exoplanets are theoretical. In the intervening decades, new instruments and methods have acted together to form one giant, interdisciplinary zoom lens on our planetary companions in the solar system. We now not only have hi-res images of planets, we can also predict their weather, dig for water under their surfaces and send spacecraft through icy plumes on their moons. Planet by planet, here's a quick guide to how our vision of the solar system has changed in the past 30 years.