Of all the spacecraft humans have launched, there have been some impressively fast movers. But which holds the record? It’s not an entirely idle question. Apart from the wow factor, it’s an interesting yardstick for gauging our capacity to explore the cosmos, from familiar planets to the icy depths of space. However, as I quickly [...]

Far from the Sun planetary bodies can hold onto many more moons. The latest count for Pluto is five satellites, and the most recent two need names. Back in 2011 and 2012 it was announced that Hubble Space Telescope observations of the Pluto system had spied first one and then another new candidate moon. For [...]

Pluto is certainly the most famous (and beloved) object among the group that astronomers call dwarf planets, but for years it’s appeared to rank a distant second in terms of size. Eris, a dwarf planet discovered in 2005, has been estimated to be as much as 700 kilometers larger than Pluto in diameter. But a [...]

Pluto’s controversial demotion from planetary status came in 2006 after the rapid discovery of comparably sized bodies—now named Haumea, Makemake and Eris—made Pluto look rather ordinary. In particular, Eris was found to be larger in diameter than Pluto, raising the question of what separated a planet from numerous smaller bodies. The International Astronomical Union decided [...]

[The text below is a modified transcript of this video.] 5) Supernova Space Rays Here on Earth, we’re under constant attack from space. Charged particles, primarily protons, crash into our atmosphere at close to the speed of light. We call them cosmic rays and we’ve finally found out where they come from. In order to [...]

Mike Brown always wanted to discover a planet. On August 25, 2006, Mike Brown killed Pluto. Well, the truth is Pluto had been killed long before, but it wasn’t until August 25 that the International Astronomical Union met, in Prague, to have the official vote. And it wasn’t until August 25 that the press conference [...]