Astronomy

If you could board a spaceship capable of flying in a perfectly straight line forever, what would happen? Common sense says you’d travel through endless galaxies, never reaching an edge, never looping back. But common sense might be wrong. The universe could be finite — and if you flew far enough, you might eventually return to where you started, having circumnavigated all of existence like a cosmic Magellan. The question of whether the universe wraps back on itself — its topology — is one of the deepest and most persistently overlooked questions in cosmology. Now, a comprehensive review from the COMPACT Collaboration, invited for publication in Nature Astronomy, lays out everything we know, everything we don’t, and the astonishing possibility that the evidence may already be hiding in data we’ve already collected.

If you could look back in time at a newborn super-Earth and a newborn mini-Neptune, you might not be able to tell them apart. Both are worlds somewhere between the size of our planet and Neptune — a category of planet that doesn’t even exist in our solar system. Both orbit alien suns in the same stellar neighbourhoods. And yet, as a team of Chinese astronomers has now shown, these two types of planet followed radically different life paths. The scars are written in the shapes of their orbits.